Moving soil on slopes. The earthen bed on the slopes is arranged in the form of an embankment, half-excavation, half-fill, excavation. Soil excavation by earth-moving machines

General Provisions. Subgrade construction highways in mountainous terrain, as a rule, it is complicated by the fact that in the places where the route is laid there are steep slopes with intensive manifestation of exogenous processes (landslides, landslides, falls, taluses) in a certain area of \u200b\u200bshort length In connection with this, it is recommended when drawing up a project for the production of works (PPR) take into account the geotechnical features of a site or a group of sites that differ in the indicated characteristics. It is recommended to designate the technology for the production of work on the construction of the roadbed, taking into account the design features of the embankment or excavation, the construction region as a whole, the structure of the slope (slope) and the properties of the constituent rocks.

In the PPR, it is necessary to provide for a set of technological measures to ensure the stability of natural slopes and slopes of excavations during the construction and subsequent operation of the road.

When developing PPR, choosing technology, machines and method of drilling and blasting operations, the presence of cracks in the developed massif and the nature of the layering of sedimentary rocks are taken into account.

Availabilitycracks in rocky igneous rocks reduces the stability of slopes and slopes of excavations. The fall of cracks at an angle of more than 35 ° towards the road contributes to the occurrence of landslides, landslides, falls already in the process of work. Falling cracks towards the massif is safe.

Layering leads to a weakening of the massif in the slopes and slopes, especially when trimming or undermining.

With an increase in the angle of the strike of the bedding with the longitudinal axis of the road, the stability of the slopes and slopes increases sharply. The most stable position of the bedding meeting angle in relation to the road axis will be 90 °. When the azimuth of the bedding strike coincides with the direction of the road axis, the undercut or undermined slopes and slopes of the excavations are destroyed only along the bedding planes.

When building roads in mountainous conditions, the main difficulties are associated with the development of rocks, a reduction in the front of work, limited transport accessibility of the working area, movement, leveling, compaction of coarse soils, and finishing work.

If the working area is inaccessible for the direct operation of machines, the first stage of construction should include the laying of a pioneer road along the projected route. If the laying of the pioneer road along the projected route is impossible, it is arranged as close as possible to it with approaches to the work area of \u200b\u200bindividual structures. In this case, a footpath is laid along the route itself.

Loosening and mining of rocks belonging to the V group and higher in terms of mining difficulty is carried out by the blasting method. The blasting method is also recommended to be used for the formation of deep excavations by massive explosions for release or purposeful explosions for the construction of embankments in hard-to-reach places of mountainous terrain.

At all stages of the work, measures should be constantly taken on slopes and slopes to prevent geodynamic phenomena (landslides, talus, avalanches, etc.) that can pose a danger to working people, equipment, structures. For these purposes, before the start of work, as well as in the process of developing mountain slopes, constant monitoring of the stability of both individual rock fragments and the entire slope from the upstream side should be organized. If signs of instability are found, safety measures must be taken immediately, such as demolishing and removing overhanging boulders. In the presence of active landslides, intensive landslides, large falls, drilling and blasting operations are performed only for loosening with small-hole charges.

Work on the construction of the subgrade on slopes, stable and landslide slopes include: a preparatory complex associated with laying out works, removal of vegetative soil; construction of a drainage system, parking for equipment, special anti-landslide structures; basic work on the construction of the roadbed, located on various elements of the slope relief or in its environment, and a set of anti-landslide measures.

It should be borne in mind that the choice of technology is also associated with the need to develop deluvial, rocky or semi-rocky rocks, as well as their use in the form of coarse soils for filling embankments. The latter depends on the passage of the route in highly rugged terrain.

Construction of embankments and excavations. The construction of a roadbed in a mountainous area includes the device of the following structures, depending on the conditions of the route in a specific region and area of \u200b\u200ba mountainous area, their hypsometric, geomorphological and engineering-geological features: a subgrade in a shelf, a half-fill-half-excavation, an excavation in a rock mass, an embankment from rocky or coarse soils.

The choice of technology for the development of excavations and the construction of embankments is determined by the design features of the roadbed, the category of rocks according to the difficulty of their development, the sources of obtaining rocky or coarse-grained soil for the roadbed of the embankments.

Construction of subgrade in shelves on pressure areas with a slope steepness of more than 1: 3 in rocks, it is carried out by blasting, followed by excavation of the blasted mass, and its transportation to the embankment sections. In the presence of deluvial deposits on the slopes, the subgrade in the shelf is developed by first cutting the slope with powerful bulldozers of the 250-300 tf class, followed by refinement by excavators and transportation of coarse soils by dump trucks.

Construction of embankments and notches on slopes with a steepness of 1: 3 or more is performed by the method of sequential cutting of flanges for recesses or semi-recesses or ledges at the base of the embankment. Cutting of ledges (shelves) is performed, as a rule, starting from the upper tier. When the stability of the slope is ensured and the need to create a passage for drilling operations, the first shelf is developed at the level of the lower edge of the excavation (shelf).

Excavation of rock cuttings they are carried out at once with a little overkill in order to avoid the subsequent difficult and expensive work to remove an under-selected thin layer of rocky soils. The subgrade is leveled to the design marks with fine torn stone and rubble.

The development of excavations in deluvial soils, softened and highly weathered demountable, fractured rocks is recommended to be carried out according to the "sliding shelf" scheme, when, after the implementation of the pioneer trench-face, necessary for placing and safe work excavator, to it from top to bottom the soil is developed and moved by powerful bulldozers of class 250-300 tf. With the help of an excavator, the soil is further processed and loaded into vehicles with movement to the embankment construction sites.

For the formation of flat surfaces of slopes during the construction of excavations and semi-excavations in favorable engineering and geological conditions (weak fracture toughness of rocks, separation into rectangular parts with vertical direction of separation planes, the ability of rocks to brittle cleavage, etc.), contour blasting is used.

The choice of the method and parameters for loosening rocky and coarse-grained soil should be carried out in accordance with the group of soil according to the difficulty of development, with the area and conditions of its application. If the calculated amount of oversized in the loosened soil and their maximum size is exceeded, it is necessary to make appropriate changes to the scheme and parameters of loosening.

Prior to drilling and blasting operations, the vegetation cover, fertile soil layer and overburden are removed and removed. When the thickness of the overburden is not more than 1/3 of the depth of excavation, loosening of the rocky soil is allowed without removing them.

Drilling and blasting works and loading of loose rock with excavators can be carried out in parallel. In this case, the first work should be carried out ahead of time. If the method of borehole charges is used for loosening in grooves or benches up to 5 m deep, drilling and blasting operations should be performed ahead of time, providing at least a replaceable stock of blasted rock. At the same time, the minimum lead distance must be maintained in accordance with the Unified Safety Rules for Blasting Operations (Moscow: Nedra, 1985).

Before starting the excavator, the oversized items located in the upper layer of the blasted soil are crushed by additional explosions. In the process of excavation, oversized items are rolled to the side and then also crushed by explosions, moving the blasted rock with a bulldozer to the excavator face.

When developing semi-cuts on the rocky slopes, at first, a shelf for a working passage with a width of 3.5 m is arranged, which provides the possibility of passage of the main machines (drilling rigs, excavators, bulldozers, dump trucks, etc.). Then the shelf is widened, bringing the subgrade to the design outline.

When designing recesses loosening of rocks to the required particle size must be ensured by the proper technology of drilling and blasting operations and proceed from the required compaction conditions stipulated by SNiP 2.05.02-85. Crushing of large oversized debris is carried out by overhead charges. This method is used with limited compressor capacity or in the absence of hammer drills and a small amount of oversized. The rock ledges remaining on the slopes and the main excavation site are also crushed.

With explosive methods of development and loosening, shortages at the base of the excavations are not allowed. Shortages on the surface of the slopes should not exceed 0.2 m, provided that their stability is ensured. The amount of overkill after the final cleaning of the bottom and slopes of the excavations should not be more than the values \u200b\u200bindicated in table. one.

When reworking excavations in rocky soils after explosions for release, the following work procedure should be observed:

crushing oversized materials located on the surface, formed during the explosion of the trench;

leveling heaps of loosened soil with a bulldozer;

removal of blasted soil from slopes by an excavator (trimming of slopes);

removal of non-hanging stones and canopies with an excavator and small explosions;

completion of the excavation to the design outline by explosions; alignment of the main platform.

Table 1

Note. During drilling operations under water and in offshore areas and roadsteads, the sizes of overruns are established by the construction organization project.

In case of longline excavation, each layer must be modified to the design contour and cleaned before starting work on the next layer.

When constructing embankments from coarse soils, which are the product of loosening or weathering of rocks, the maximum particle size of the block fraction should be assigned depending on the thickness of the compacted layer, the type and technical parameters of the compaction means and the physical and mechanical characteristics of the soil, but should not exceed 2/3 of the thickness of the compacted layer.

Oversized debris, the dimensions of which do not meet the specified requirements, may be placed in the side (slope) parts and in the lower layer of the embankment in one row so that they do not fall into the working layer of the embankment.

When laying oversized debris in the base of the embankment, to avoid uneven sediment due to spillage of fine-grained aggregate from the overlying layers into the underlying layers, intermittent layers of crushed stone (pebble), sandy or clayey soils should be arranged.

The filling of the embankment from coarse-grained soils is carried out by a bulldozer in the "away from oneself" method so that the largest fragments are located in the lower parts of the embankment. The most rational use of a bulldozer with a universal blade, which allows in the distribution process to reject oversized items with their subsequent laying in the side of the embankment.

There are two schemes for the distribution of coarse soil: longitudinal and diagonal. Depending on the method of soil filling, the longitudinal and diagonal distribution patterns can be one-sided or two-sided.

With axial filling, a two-sided distribution scheme is used, with lateral filling - one-sided.

It is rational to use specially equipped dumps with a mixed sorting device like a ripper for rejecting oversized items.

Before compaction, the lateral parts of the embankment, including the slopes, made of oversized bulk, are leveled with soil of smaller fractions. When constructing a subgrade on slopes with a steepness of more than 1: 3, it is advisable to arrange leveling from soils with sand filler according to the method of splitting.

The development of coarse soils after blasting operations is advisable to be carried out by an excavator with a bucket capacity of 0.65-1 m 3 with loading into vehicles. If it is necessary to huddle the soil of an oversized dump on horizontal surfaces and slopes with a steepness of up to 1: 3, bulldozers are used.

With a layered bedding of easily weathered softened rocks, alternating with layers of clay soils, the development is carried out to the entire thickness of the face, taking into account that the developed soils contain 30-40% (by weight) of clayey fine earth. Otherwise, development is carried out in separate layers.

Stylingand compaction of coarse soils. Coarse-grained soils of frame and imperfect frame structure made of durable water-resistant rocks should be compacted, as a rule, by vibration method. Coarse soils containing more than 30% clay aggregate are compacted at a moisture content not exceeding the permissible values \u200b\u200bfor heavy sandy loams and light loams, and with a clay aggregate content of less than 30% - at a moisture content not exceeding the permissible values \u200b\u200bfor light and silty sandy loams.

Compaction of coarse-grained soils, the strength of which is less than 5.0 MPa (50 kg / cm 2), should be carried out in two stages: at the first - with lattice rollers; on the second - with rollers on pneumatic tires with a mass of at least 25-30 tons. When using softened coarse soils, work should be carried out in dry weather with minimal gaps in time between separate technological operations.

Methods and technical means of compaction of easily weathered non-water-resistant coarse-grained soils are prescribed from the condition of ensuring the destruction of aggregates until the pores are filled with fine earth. To increase the efficiency of destruction of aggregates, they are periodically moistened.

Good results are obtained by the technological scheme of compaction in two stages: at the first (immediately after leveling and moistening) - with lattice rollers, which carry out additional crushing of the soil, at the second - with heavy rollers on pneumatic tires. The required degree of soil compaction is achieved after 10-12 passes along one track of rollers on pneumatic tires weighing 25-30 tons. For coarse-grained soils of low strength, compaction by tamping is effective.

If it is impossible to ensure the destruction of aggregates of non-water resistant rocks, they should be protected in the embankment from the effects of weather and climatic factors. When installing protective layers of clay or loamy soils, the latter are poured to a predetermined thickness, layer by layer, flush with the layer of detrital soil and compacted together with it.

When installing a protective layer 15-20 cm thick from soils strengthened with organic binders, the soil is pre-mixed with binders in stationary or mobile installations and transported by dump trucks to the place of laying. Bulldozers or leveling excavators are recommended for spreading the mixture on the surface of slopes. Platform vibrators or vibrating screeds moved along the slope from top to bottom or bottom to top can be used as sealing means.

Quality control of work when constructing a subgrade on slopes, stable and landslide slopes, in addition to the general requirements provided for by SNiP 3.06.03-85, includes: control over the restoration, consolidation and breakdown of the subgrade on the marked relief elements; quality control of ledges cutting (in compliance with the design geometric parameters), compliance with the technology for the development of slopes and slopes when constructing a subgrade in the ledge and the sequence of a complex of anti-landslide measures (drainage, drainage and retaining structures).

Organization of works on the construction of highways in the presence of landslides, it includes two independent issues: the construction of the subgrade and the construction of a complex of anti-landslide structures established by the project. The sequence of these works is determined by the specific conditions of the territory, the location of the subgrade, the composition and types of anti-landslide structures and should be stipulated in the design and calculation documentation. In practice, there are several options for organizing the sequence of earthworks and the device of anti-landslide structures: construction of a complex of anti-landslide structures before the construction of the subgrade; implementation of anti-landslide structures during its construction; construction of anti-landslide structures after the construction of embankments or excavation.

As a rule, the first scheme is most expedient when constructing a road on landslide slopes, when the construction of the subgrade is possible only under the direct protection of supporting structures or after taking measures to regulate surface and underground runoff. The second scheme is used when the subgrade is located in deep excavations and high embankments. For example, as each tier is developed, slopes are strengthened and drainage structures are constructed. The third scheme is used in many cases in the construction of roads in mountainous conditions, when, in particular, after the installation of the subgrade, upper retaining walls or anchor structures are erected in the shelf.

Of course, the variety of complex conditions for the construction of highways in landslide or potentially landslide areas requires the creative application of these schemes with the subsequent development of specific technological and organizational solutions in work projects. IN this section only general issues of organizing construction in landslide areas are considered and the specifics of construction are not covered specific types landslide structures, which is reflected in other chapters.

In addition to the features associated with the sequence of earthworks and the construction of anti-landslide structures, it should be noted that the technology of earthworks production largely depends on the design principles (in relation to the relief) of highways. There are the following types of individual technological schemes organization of earthworks: development of deep excavations and construction of high embankments; construction of embankments on slopes with the intersection of landslide areas; the device of the subgrade in the shelves. One of the most difficult cases of work is carrying out them at emergency facilities, when landslides have destroyed sections of operated roads.

The fact of violation of the stability of natural slopes and slopes of the subgrade established by repeated surveys during the construction of highways in various regions of our country convincingly shows that the influence of technological factors can be significant, and in some cases prevail.

Technological factors in this case include: the method and time for the development of excavations or the construction of embankments, the method and time for the construction of anti-landslide structures. These factors can be combined into a general technological system for the construction of individual structures of the subgrade, which, during its implementation, will have certain effects on the stability of the slopes of the subgrade and adjacent slopes, especially landslide ones.

The analysis of the construction of highways in landslide areas showed that the impact of the technological system on the stability of slopes and slopes is manifested in the following.

An unsuccessfully chosen direction of work in the development of deep excavations can lead to the development of landslides in the slopes. The degree of intensity of excavation work affects the parameters of the stability of slopes during the construction process. So with a short front of work and a high speed of excavation in the slopes (at the working depth of development), deformations do not have time to occur, leading to landslides, which allows you to give the slopes of the working tiers more steep angles. The construction of high embankments and embankments on slopes (including landslide ones), on the contrary, requires a slower mode of soil filling, due to the need for thorough soil compaction, as well as the gradual transfer of the load from the weight of the embankment to the slope foundation, which ensures its stability and further stability.

The order and timing of their design configuration have a significant impact on the development of landslides on slopes and slopes. The most common mistake in this regard is associated with the construction of berms, longlines, drainage structures and strengthening works on the slopes, not during the development of excavations and construction of embankments, but after their completion. Of particular importance is technological sequence construction of embankments on the slopes. In projects for the production of work, such a principle of work should be laid down, which would guarantee the stability of the inclined base during the construction of the subgrade. In particular, for example, in many cases, the stability of the embankments on the slopes was disturbed due to the wrong method of work: instead of sequential construction of the embankment on the lower side of the slope, work was carried out from the upper side, which led to the development of unconsolidated zones in the slope parts, overstressing of the slope base the development of landslides both in the slopes and in the slopes of the embankments.

Technological factors become very important when carrying out earthworks on landslide slopes or in their environment. Correct placement of earthmoving equipment, determination of the required pace, maintaining the required development depth or slope steepness provide not only the possibility of implementing design solutions, but also their further reliability during the operation of the road section, as well as the degree of preservation in a stable state of the landslide slope itself.

The choice of the method for the production of earthworks depends on the properties of the soil, the amount of work, the type of earthworks, hydrogeological conditions and other factors. The technological process of performing earthworks consists of soil development, transportation, laying in a dump or embankment, compaction and leveling. For the mechanization of earthworks, single-bucket construction excavators with flexible and rigid suspension of working equipment in the form of a forward and backward shovel, dragline, grab, earthmoving, leveling and loading devices are used; continuous excavators, which include multi-bucket chain, scraper chain, multi-bucket rotary and bucket-free rotary (milling) excavators; bulldozers, scrapers, graders (trailed and self-propelled), graders, elevators, rippers, boring machines. In addition to the leading earth-moving machine, the set of machines for mechanized soil excavation also includes auxiliary machines for transporting soil, cleaning up excavation of the bottom, compaction of soil, finishing slopes, preliminary loosening of the soil, etc., depending on the type of work.

Soil excavation with single-bucket excavators

In industrial and civil construction, excavators with a bucket with a capacity of 0.15 to 4 m3 are used. When performing large volumes of earthworks in hydraulic engineering, more powerful excavators with a bucket capacity of up to 16 m3 or more are used.

Wheeled excavators are recommended to be used when working on soils with high bearing capacity with dispersed volumes of work, when working in urban environments with frequent relocations; crawler excavators are used for concentrated volumes of work with rare relocations, when working on soft soils and developing rocks; mounted excavators on pneumatic-wheeled tractors - for scattered volumes of work and when working in off-road conditions.

The excavation of the soil with single-bucket excavators is carried out by sinking. The number of penetrations, faces and their parameters are provided for in projects and technological maps earthworks for each specific object in accordance with the parameters of earthworks (according to working drawings) with the optimal working dimensions of excavator equipment.

Single bucket excavators are cyclic machines. The working cycle time is determined by the sum of individual operations: the duration of filling the bucket, turning to unload, unloading and turning into the face. The smallest time spent on the execution of the working cycle is ensured under the following conditions:

• the width of penetrations (faces) is taken in such a way as to ensure the operation of the excavator with an average turn of no more than 70 degrees;
• the depth (height) of the faces must not be less than the length of the soil shavings required to fill the bucket with a heap in one digging;
• the length of penetrations is taken taking into account the smallest possible number of inputs and outputs of the excavator into and out of the face.

The face is called the working area of \u200b\u200bthe excavator. This zone includes the site where the excavator is located, part of the surface of the developed massif and the place for installing vehicles or the site for laying the excavated soil. The geometric dimensions and shape of the face depend on the equipment of the excavator and its parameters, the size of the excavation, the types of transport and the adopted soil development scheme. In the technical characteristics of excavators of any brand, as a rule, their maximum indicators are given: cutting radii, unloading, unloading height, etc. During excavation work, optimal operating parameters are taken, which are 0.9 of the maximum passport data. The optimal height (depth) of the face should be sufficient to fill the excavator bucket in one dig, it should be equal to the vertical distance from the horizon of the excavator parking to the level of the pressure shaft, multiplied by a factor of 1.2. If the face height is relatively small (for example, when developing a grading cut), it is advisable to use an excavator together with a bulldozer: the bulldozer develops the soil and moves it to the excavator's workplace, then heaps the soil, while ensuring a sufficient face height. The excavator and vehicles should be located so that the average angle of rotation of the excavator from the bucket filling to the point of unloading is minimal, since the boom rotation takes up to 70% of the excavator's cycle time.

As the soil is developed in the face, the excavator moves, the worked out areas are called penetrations. In the direction of movement of the excavator relative to the longitudinal axis of the excavation, longitudinal (with a frontal or end face) and transverse (lateral) development methods are distinguished. The longitudinal method consists in the development of a cut by penetrations, the direction of which is chosen along the largest side of the cut. The frontal face is used when developing an exit to the pit and when digging the beginning of the excavation on steep slopes. With a head-on bottomhole, the soil is developed over the entire width of the penetration. The end face is used when excavating excavations below the level of the excavator parking, while the excavator, moving in reverse on the ground surface or at a level located above the bottom of the excavation, develops the end of the excavation. Sidewalls are used to develop excavation with a straight shovel, while the paths of vehicles are arranged parallel to the axis of movement of the excavator or above the bottom of the face. With the sideways method, the full penetration width can be obtained by sequentially developing a series of penetrations. In the transverse (lateral) way, excavations are developed with soil filling in a direction perpendicular to the axis of the excavation. The transverse method is used in the development of long, narrow excavations with filling of cavaliers or in the construction of embankments from lateral reserves.

Some types of excavations (for example, grading) can be developed with a sidewall with traffic on the same level as the excavator. Sometimes, in order to move to the development with a sidewall, it is first necessary to tear off the so-called pioneer trench, which the excavator begins to develop, descending to the bottom of the face along a ramp. If the unloading height of the excavator is greater than or equal to the sum of the depth of the excavation, the height of the side of the dump truck and the "cap" above the side (0.5 m), the pioneer trench is developed with a sidewall when transport is moving on the day surface at a distance of at least 1 m from the edge of the excavation. With significant excavation dimensions, it is developed by transverse penetrations along the smaller side, while ensuring the minimum length of the pioneer trench, which makes it possible to organize the most efficient circular traffic of transport. Excavations, the depth of which exceeds the maximum bottomhole depth for this type of excavator, are developed in several tiers. In this case, the lower tier is developed in the same way as the upper one, and the cars are fed to the excavator so that the bucket is on the back of the body. In this case, the route of the vehicle should be parallel to the excavator penetration axis, but directed in the opposite direction.

An excavator equipped with a backhoe is used for excavation below the parking level and is most often used when digging trenches for laying underground utilities and small pits for foundations and other structures. When working with a back shovel, an end or side face is also used. It is most advisable to use an excavator with a backhoe for excavating pits with a depth of no more than 5.5 m and trenches up to 7 m. The rigid attachment of the backhoe bucket makes it possible for it to dig narrow trenches with vertical walls. The depth of the narrow trenches being mined is greater than the depth of the excavations, as the excavator can lower the boom and stick to the lowest position while maintaining stability.

An excavator with dragline working equipment is used in the development of large and deep pits, when erecting an embankment from reserves, etc. The advantages of a dragline are a large radius of action and a digging depth of up to 16-20 m, the ability to develop faces with a large inflow of groundwater. Dragline designs cuts with face or side penetrations. For front and side penetrations, the organization of dragline work is similar to that of a backhoe. The ratio of the maximum depth of cut remains the same. The dragline usually moves between stops 1/5 of the boom length. The development of soil by dragline is most often done in a dump (one-sided or two-sided), less often - for transport.

Excavators cut pits and trenches to a depth somewhat less than the design depth, leaving the so-called shortage. The shortage is left in order to avoid damage to the base and to prevent overburdening of the soil, it is usually 5-10 cm. To increase the efficiency of the excavator, a scraper knife mounted on the bucket is used. This device makes it possible to mechanize operations for cleaning the bottom of pits and trenches and carry them out with an error of no more than plus or minus 2 cm, which eliminates the need for manual modifications.

The development of the soil by continuous excavators is carried out in the absence of stones, roots, etc. in the soil. marks (for water flow). Multi-bucket excavators mine trenches of limited dimensions and usually with vertical walls.

Soil excavation by earth-moving machines

The main types of earth-moving vehicles are bulldozers, scrapers and graders, which in one cycle excavate the soil, move it, unload it into the embankment and return empty to the face.

Excavation by bulldozers

Bulldozers are used in construction for the development of soil in shallow and extended excavations and reserves for moving it in the embankment at a distance of up to 100 m (when using more powerful machines, the distance of soil movement can be increased), as well as for clearing the territory and planning works, for cleaning the bases under embankments and foundations of buildings and structures, when arranging access roads, excavating soil on slopes, etc.

Figure: 7.:
a - conventional cutting; b - comb cutting

In the practice of earthworks, there are several ways to cut soil with a bulldozer (Fig. 7):

• ordinary cutting - the knife first goes deep to the maximum depth for a given soil and gradually rises as it is loaded, since the drag of the drag prism increases, which consumes the tractor's tractive effort;
• comb cutting - the blade is filled with several alternating depressions and elevations.

The comb pattern reduces the length of cut by increasing the average chip depth. In addition, with each penetration of the knife, the soil is chipped off under the drawing prism and the already cut soil is compacted on the blade. This reduces cutting time and increases the amount of soil on the blade.

In earthworks with bulldozers, the slope cutting method is successfully used, based on the rational use of the tractive effort of the tractor. Its essence is that when the tractor moves downhill, part of the tractive effort required to move the machine itself is released, due to which the soil can be destroyed with a thicker layer. When the bulldozer operates downhill, it facilitates the chipping of the soil, the drag of the drag prism decreases, which moves partially under its own weight. In the absence of a natural slope, it can be created with the first passes of the bulldozer. When working at a slope of 10-15 degrees, productivity increases by about 1.5-1.7 times.

Figure: 8. :
a - single-layer cutting; b - trench cutting. The numbers indicate the cutting order

The bulldozer works according to the schemes shown in fig. 8. The vegetation layer is removed by single-layer cutting with overlapping strips by 0.3-0.5 m. The bulldozer then moves the soil into the blade or intermediate shaft and returns to the new cut without turning, in reverse (shuttle pattern), or with two turns. Trenching is carried out with the leaving of lintels 0.4 m wide in cohesive soils and 0.6 m in weakly cohesive soils. The depth of the trenches is taken as 0.4-0.6 m. Lintels are developed after the passage of each trench.

Excavation with scrapers

The operational capabilities of the scrapers allow them to be used for excavating excavations and leveling surfaces, for arranging various excavations and embankments. Scrapers are classified:

• by the geometrical volume of the bucket - small (up to 3 m3), medium (from 3 to 10 m3) and large (over 10 m3);
• by the type of aggregation with a tractor - trailed and self-propelled (including semitrailer and saddle ones);
• by the method of loading the bucket - loaded due to the traction force of the tractor and with mechanical (elevator) loading;
• by the method of unloading the bucket - with free, semi-forced and forced unloading;
• by the method of driving the working bodies - hydraulic and rope.

Scrapers are engaged in development, transportation (the distance of soil transportation varies from 50 m to 3 km) and laying of sandy, sandy loam, loess, loamy, clayey and other soils that do not have boulders, and the admixture of pebbles and crushed stone should not exceed 10%. Depending on the category of soils, it is most effective to cut them on a straight section of the path when driving down a slope of 3-7 degrees. The thickness of the developed layer, depending on the power of the scraper, ranges from 0.15 to 0.3 m. The scraper is unloaded on a straight section, while the soil surface is leveled with the bottom of the scraper.

Figure: 9. :
a - with filling the bucket with shavings of constant thickness; b - with filling the bucket with shavings of variable section; c - comb method of filling the bucket with shavings; d - filling the bucket by pecking

There are several ways to cut the chips during the scraper operation (Fig. 9):

• shavings of constant thickness. The method is used for planning works;
• shavings of variable section. In this case, the soil is cut off with a gradual decrease in the thickness of the shavings as the bucket is filled, that is, with a gradual protrusion of the scraper knife towards the end of the set;
• comb method. In this case, the soil is cut with alternating deepening and gradual lifting of the scraper bucket: at different stages, the thickness of the shavings changes from 0.2-0.3 m to 0.08-0.12 m;
• pecks. The bucket is filled by repeatedly deepening the scraper knives to the greatest possible depth. The method is used when working in loose loose soils.

Depending on the size of the earthen structure, the relative position of the excavations and embankments, various scraper operation schemes are used. The most common is the elliptical pattern. In this case, the scraper turns in one direction each time.

Figure: ten. :
a - trench-comb; b - ribbed chess

When working in wide and long faces, the scraper bucket is filled with trench-comb and ribbed-checkerboard methods. With the trench-comb method (Fig. 10), the development of the face is carried out from the edge of the reserve or excavation in parallel strips of constant depth of 0.1-0.2 m, the same length. Between the strips of the first row, strips of uncut soil are left - ridges, in width equal to half the width of the bucket. In the second row of passages, the soil is taken to the full width of the bucket, cutting off the ridge and forming a trench under it. In this case, the thickness of the shavings is 0.2-0.4 m in the middle of the bucket, and 0.1-0.2 m at the edges.

In the case of the ribbed-checkerboard method (Fig. 10), the working of the face is carried out from the edge of the excavation or reserve in parallel strips so that between the scraper penetrations there are strips of uncut soil equal in width to half the width of the bucket.

The second row of penetrations is developed, retreating from the beginning of the first row by half the length of the first row. Scraper work should be combined with bulldozer work, using them to excavate elevated areas and move soil over short distances to lower places.

Excavation by graders

Graders are used when planning the territory, slopes of earthen structures, cleaning the bottom of pits and cutting ditches up to 0.7 m deep, when erecting extended embankments up to 1 m high and the lower layer of higher embankments from the reserve. The road bed, driveways and roads are profiled by motor graders. It is most effective to use motor graders with a driving length of 400-500 m. Dense soils are preliminarily loosened before mining by a grader. When erecting an embankment from the developed reserve, the inclined knife moves the cut soil towards the embankment. During the next excavation of the grader, this soil moves even further in the same direction, therefore it is advisable to organize the work with two graders, one of which cuts and the other moves the cut soil.

When erecting embankments and a profiled roadbed, soil cutting begins from the inner edge of the reserve and is carried out in layers: first, the triangular shavings are cut, then the shavings are rectangular to the end of the layer. When developing wide reserves in soils that do not require preliminary loosening, cutting begins from the outer edge of the reserve and is carried out layer by layer, with all passes, triangular shavings; another way is possible: the chips are thus obtained triangular and quadrangular.

When performing various operations, the tilt angles of the grader vary within the following limits: capture angle - 30-70 degrees, cutting angle - 35-60 degrees, tilt angle - 2-18 degrees. In construction practice, several methods of laying soil are used:

• the soil is laid in layers, pouring it from the edge to the axis of the road (grading works at zero marks with an embankment height not exceeding 0.1-0.15 m);
• the rollers are placed one next to the other with their contact only by the bases (filling of embankments with a height of 0.15-0.25 m);
• each subsequent roller is partially pressed against the previously laid one, overlapping it with a base by 20-25%; the crests of these two rollers are located at a distance of 0.3-0.4 m from one another (filling of embankments up to 0.3-0.4 m high);
• each subsequent roller is pressed against the previously laid one without any gap; the new roller is moved with the blade close to the previously laid one with a capture of it by 5-10 cm; one wide dense shaft is formed 10-15 cm above the first roller (filling of embankments up to 0.5-0.6 m high).

Development of frozen soils

Frozen soils have the following main properties: increased mechanical strength, plastic deformation, heaving and increased electrical resistance. The manifestation of these properties depends on the type of soil, its moisture content and temperature. Sandy, coarse-grained and gravel soils with a thick layer, as a rule, contain little water and almost do not freeze at subzero temperatures, therefore, their winter development is almost the same as summer. When excavating in winter pits and trenches in dry loose soils, they do not form vertical slopes, do not heave and do not sag in spring. Dusty, clayey and moist soils change their properties significantly when frozen. The depth and rate of freezing depends on the degree of soil moisture. Earthworks in winter are carried out by the following methods:

• by the method of preliminary preparation of soils with their subsequent development by conventional methods;
• by the method of preliminary cutting of frozen soils into blocks;
• by the method of soil development without preliminary preparation.

Preliminary preparation of the soil for development in winter consists in protecting it from freezing, thawing frozen soil and preliminary loosening of frozen soil. The simplest way to protect the soil surface from freezing is to insulate it with thermal insulating materials; for this, peat fines, shavings and sawdust, slag, straw mats, etc. are used, which are laid in a layer of 20-40 cm directly on the ground. Surface insulation is used mainly for recesses that are small in area.

To insulate large areas, mechanical loosening is used, in which the soil is plowed with tractor plows or rippers to a depth of 20-35 cm, followed by harrowing to a depth of 15-20 cm.

Mechanical loosening of frozen soil at a freezing depth of up to 0.25 m is carried out with heavy rippers. When freezing up to 0.6-0.7 m, when cutting small pits and trenches, the so-called loosening by splitting is used. Impact permafrost rippers work well at low soil temperatures, when it is characterized by brittle deformations that contribute to its splitting under the impact of an impact. A diesel hammer with a wedge is used to loosen the soil at a large freezing depth (up to 1.3 m). Development of frozen ground by cutting consists in cutting mutually perpendicular furrows with a depth of 0.8 of the freezing depth. The block size should be 10-15% smaller than the excavator bucket size.

Thawing of frozen ground is carried out using hot water, steam, electric current or fire. Defrosting is the most difficult, time consuming and expensive method, therefore it is used in exceptional cases, for example, during emergency operations.

© 2000 - 2009 Oleg V. site ™

Soil can be worked in three main ways: cutting - earth-moving (single-bucket excavator with interchangeable equipment "forward" and "reverse" shovels and multi-bucket rotary or chain excavator) and earth-moving (scraper, bulldozer, grader) machines; hydromechanical - with the help of water monitors and dredgers in the presence of powerful sources of water supply, while soil erosion and its supply to the place of laying occur due to the kinetic energy of the water jet; explosion using various explosives. In addition to the above, there are special methods of soil destruction - ultrasound, high-frequency currents, thermal installations, combined methods.

Soil development by cutting

Development of soil by earth-moving mechanisms (single- and multi-bucket excavators). Excavators are single-bucket cyclic action on pneumatic or caterpillar tracks and multi-bucket continuous action. Single-bucket excavators are equipped with various replaceable equipment (Fig. 1.7).

Slaughter is called the excavator's workplace, including the place of its standing and soil intake. A penetration is a recess formed by a single excavator stroke. Passages are: frontal (end), in which the development is carried out on steep slopes along the axis of the excavation and in front of itself and on both sides of the axis, and lateral, in which the development of the soil occurs from one side in the direction of travel. Excavations of considerable depth are developed in tiers-ledges arranged at different levels. Vehicles are positioned at or above the excavator level. Diagrams of frontal penetrations of an excavator with "forward" and "back" shovels are shown in Fig. 1.8: longitudinal symmetrical, longitudinal with lateral movement, zigzag.

Figure: 1.7. Types of construction excavators with various interchangeable equipment: a - straight shovel; b - back shovel; in - grab; g - dragline; d- pile driver for driving piles; e, and - crane for installation and handling operations; to - diesel hammer for loosening frozen soil; f - device for removing stumps

The development of dense soils in the face plane is carried out in a checkerboard pattern, i.e. offset from the previous cutting strip by an amount less than the bucket width. When the boom is turned in the opposite direction, strips of uncut soil are removed, which ensures quick filling of the bucket with soil, since the lateral cutting resistance is thereby reduced. Sandy soils are developed in successive strips (shavings) with a slight overlap of the previous strips.

Multi-bucket excavators are divided according to the type of main working equipment into chainused in the development of soft soils of category 1-3 at a depth of less than 4 m, and rotaryused for soils of increased strength, including frozen ones, at a depth of less than 2.5 m. Development of soil by rotary and chain excavators in cohesive soils (clay, loam) is carried out to a depth of 3 m without additional fastening.

Figure: 1.8. Soil excavation with single-bucket excavators when excavating pits: a - frontal driving of an excavator equipped with a straight shovel, with one-sided loading into a transport vehicle; b - the same, with two-way loading; in - widened frontal penetration with a zigzag movement of the excavator; d - the same with the movement of the excavator across the pit; d - side driving of an excavator equipped with a straight shovel; f, g, h - end driving along the foundation pit with an excavator equipped with a backhoe; and, k - the same, when driving across the pit; l - lateral penetration; m - cross-shuttle penetration

dragline excavator

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Development of soil by earth-moving machines. Trailed, semi-trailed and self-propelled scrapers are used depending on the type of interconnection between the working equipment and the tractor. Scrapers are used when planning an area and arranging linear-extended earthworks (Fig. 1.9).

The possibility and conditions of soil development with a scraper are determined by the consistency of the soil (B): B \u003d (IV- N / r) / (IV, - Щ,), Where IV- natural soil moisture,%; Щ, - soil moisture at the border of rolling,%; IV, - soil moisture at the yield point,%. With a hard soil consistency (B 0) and semi-solid ( B \u003d 0-0.25), the soil should be loosened beforehand. With a stiff-plastic consistency (IN- 0.25-0.5) and soft-plastic consistency (5 \u003d 0.5-0.75), the soil can be developed without loosening. With ductile ( IN-0.75-1) and viscous (?\u003e 1) consistency scrapers cannot be used.

Figure: 1.9. The sequence of technological operations performed by the scraper: a - loading the bucket with soil with a pusher;

b - unloading soil from the bucket

The full working cycle of soil development includes: cutting and filling the bucket, moving, unloading, laying in an even layer and compaction with the scraper wheels. The bucket is filled while the scraper moves with the knife lowered. Cutting can be performed along the following profiles: smooth shavings (Fig. 1.10, c) (used for leveling work); shavings of variable cross-section from 20 to 36 mm with a comb profile (Fig. 1.10, b); wedge profile (Fig. 1.10, and).

Figure: 1.10. Soil cutting profiles with a scraper: a - wedge-shaped shavings; b - comb shavings; in - fine chips of constant size

Depending on the direction of the soil intake in relation to the axis of the excavation, a transverse or longitudinal scheme of soil transportation can be selected. Transverse the transportation scheme is adopted with a close relative position of the cut and embankment. With this scheme, it is necessary to arrange entrances to the embankment and exits from it. When longitudinal The loaded scrapers move along a dumped embankment with two end ramps. The main part of the scraper's working cycle is its movement to and from the unloading point. The most common scraper movement patterns are: by ellipse, used in the planning of sites and filling of embankments from reserves with a limited number of captures (Fig. 1.11 , and); figure eight - with a work front that allows twice during the cycle to take soil in reserve and unload it into an embankment (Figure 1.11, b); in a spiral - at low embankments, if large volumes of work on the arrangement of ramps are not required (Fig. 1.11, d); zigzag - with columnar development of soil in reserves of great length (Fig. 1.11, c) cross-shuttle -with a concentrated movement of soil masses and a large distance from each other (Fig. 1.11.5); longitudinal shuttle (Fig. 1.11, c); at one end of the embankment and alternating embankments (fig. 1.11 , g, h).

Technological schemes for the development of soil by a bulldozer. Bulldozers are used for the development of shallow excavations up to 2 m or embankments with a height of less than 1.5 m with the movement of soil into the dump at a distance of up to 200 m; for rough site planning; backfilling of trenches, pits sinuses; hilling soil in the area of \u200b\u200bloader operation, as well as an additional tractor when excavating soil with scrapers. The maximum cutting depth is 20-60 cm. The working body of the bulldozer is a straight hinged blade, rigidly fixed and rotated in the vertical (90-54 °) and horizontal (3-8 °) planes.

Dozer cutting profiles are the same as scraper cutting profiles. The most rational are wedge-shaped and comb cutting schemes. When excavating soil in wide openings and on sites, several technological schemes can be used (Fig. 1.12), which provide the highest productivity: transverse with long-trench excavation; trench according to the shuttle scheme (when developing foundation pits); continuous layer; step-tiered; stripes; trench-strip, etc. In the trench method of soil development between the parallel penetrations of the bulldozer, they leave untouched earth shafts bordering the trenches and preventing soil loss.

The shafts are bulldozed last. When moving over a distance of more than 40 m, the development method with an intermediate shaft or the paired operation of bulldozers moving next to the same speed at a distance of 0.5 m from each other is used. With the shuttle scheme (in shallow and wide recesses), the soil is cut and moved in the pit along the axis of the pit, starting from the middle,

round trip. First, a pit is developed at the first capture to a depth of 1 m, and then at the second at the same depth, etc. Bridges of untouched soil and shafts 0.5-1.2 m wide are left between adjacent trenches, which are cut off after several trenches have been developed. When constructing linear structures of small width, the soil is developed according to the scheme ellipse or eight.

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soil collection soil unloading

scraper travel direction

Figure: 1.11. Soil development scheme with scrapers: a - along an ellipse; b - figure eight; in - zigzag; d - in a spiral; d - cross-shuttle; e - longitudinal shuttle; g - when reserves or excavations are located at one end of the embankment; h - during development

notches alternating with embankments

hut for the device of the subgrade trough; leveling of soil, poured into an embankment with a height of no more than 1.2 m; cuts and grading of slopes of excavations and embankments; profiling the earthen trough of the sand layer; leveling crushed stone; mixing road building materials with binders; devices for diverting ditches and upland ditches up to 0.7 m deep. The main grader body is a blade with a knife for cutting and moving the soil and an auxiliary scarifier used for removing small stumps, roots, loosening soils and road surfaces (Figure 1.13).

Design surface

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Figure: 1.12. Methods and schemes of soil development by bulldozers: a - paired work; b - shuttle scheme; c - layer-by-layer development;

d - layer-by-layer filling; d, e - in piles without layer-by-layer compaction; g - development of soil "from the head"; 1-7 - sequence of movement of the bulldozer; 8- soil moved by a single bulldozer;

9- additional volume of soil moved by two bulldozers; I-VII - sequence of soil development during planning

Figure: 1.13. The position of the grader blade: a - transport; b - blade installation at an angle (3; c, d - the same at different angles

to the horizontal plane

The development of soil by a motor grader is performed by removing rectangular and triangular shavings, which depends on the adopted scheme of work in reserve. When erecting an embankment, the most rational is the layer-by-layer cutting of the soil of rectangular shavings, and when developing the soil from the outer edge of the reserve to the inner one, cutting is performed by removing triangular shavings. During the operation of motor graders, various methods of laying the soil are used - in a press-down, half-crimp, in staggered, a layer with a given slope, etc. (fig. 1.14). Laying the soil press produced by rollers pressed against each other without a gap (with embankments up to 0.7 m high).

With the method half-pressed the soil is poured into the shafts with partial pressing to the previously laid, overlapping its base by "/ 4 width (with an embankment up to 0.5 m high). at random the soil is poured with shafts that touch only the base (with an embankment up to 0.25 m high). When carrying out profiling works, the soil is laid layers with a thickness of 10-15 cm, and soil filling is carried out from the edge to the axis of the road with a given transverse slope. The lack of soil in 5-7 cm to the design mark in the pits and trenches is cleaned up manually. Sometimes, instead of manual methods, soil compaction is used by mechanical vibratory ramming.

Filling the sinuses of trenches with soil is carried out with bulldozers according to a shuttle or cross-shuttle scheme, as well as manually. The filling of the sinuses is necessarily accompanied by soil compaction, which is carried out in layers. The thickness of the first compaction of the layer is 1 m, and of the subsequent layers - 0.4-0.6 m.If it is impossible for the worker to access the narrow sinus (laid collector), the soil is leveled with a micro-bulldozer, and then with a small-sized bulldozer, compacted with a self-propelled rammer. The soil in the sinuses of the collector is compacted with parallel passages of a small-sized vibratory ram-

coy. Backfilling is performed immediately after laying the pipes in order to avoid collapse of the trench walls from precipitation, overdrying or wetting of the soil in the dumps.

Figure: 1.14. Methods of laying soil into the body of the embankment by a grader (dimensions in m): a - press down; b- half-pressed; in - at random; r - in layers; d - a diagram of the work of a column of motor graders during layer-by-layer leveling of the soil in the embankment; e - grading of embankment slopes with a steepness of 1: 3 by a motor grader; 1 - the first cut of the bead No. 1; 2- passes for moving roller No. 1 to the place of laying; 3 - the second pass for cutting the bead No. 2; 4 - passes for moving roller No. 2 to the place of laying;

C is the length of the working grip; / 1 - reserve width; / 2 - embankment width;

/ 3 - the width of the roadbed

V... Preparation of foundations for embankments

1. Cutting off vegetation and cutting benches on slopes

On horizontal terrain, as well as on slopes with a steepness of up to 1:10, embankments with a height of more than 0.5 m on a dry and solid foundation are poured directly onto the natural surface, and vegetation (turf) is removed at the base of embankments up to 0.5 m high.

With a slope steepness from 1:10 to 1: 5 at the base of embankments up to 1.0 m high and at zero places, sod is also removed, and at the base of embankments more than 1 m high, sod is not cut off, but before filling the embankment from clay soils, the base surface is loosened ...

Within the slopes with a steepness from 1: 5 to 1: 3, regardless of the height of the embankment, they arrange ledges with a width of 2 to 4 m, but not less than 1 m, and a height of up to 2 m with a transverse slope to the downstream side of 0.01-0.02.

Removal of vegetation cover and cutting of benches are performed by bulldozers or motor graders.

On a slope, it is advisable to cut off the vegetative soil during the working movement of the bulldozer or motor grader from top to bottom. In this case, the soil is laid from the lower side of the embankment into the berm or removed.

The cutting of ledges can be done before the erection of the embankments from top to bottom (Fig. 29, a), starting from the upland border of the embankment slope or in the process of erecting the embankment from the bottom up (Fig. 29, b), starting from the submontane border of the embankment slope. In the first case, the width of the benches should be at least 3 m (based on the installation of the bulldozer), and in the second case, it can be reduced to 1 m.The lower ledge in both cases must be made at least 4 m wide in order to accommodate the unloaded from dump trucks soil and soil compaction machine when erecting an embankment.

The ledges are cut with a bulldozer or motor grader. The most effective is a universal dozer with a dozer that is installed at an angle to its longitudinal axis.

When cutting ledges from top to bottom, before the erection of the embankment, the soil is moved by a bulldozer in the longitudinal or transverse direction. In the latter case, it is placed in a berm.

Cutting ledges from bottom to top is carried out as the embankment is being erected. First, the lower ledge is cut, in the place of which the layers of the embankment are then poured. After filling the soil layer to the level of the top of the ledge, the next ledge is cut, etc. The ledge soil is leveled along the width of the filled layer, if it is suitable for laying in an embankment, or removed outside the embankment.

It is advisable to use a motor grader to give the ledges a transverse slope.

2. Arrangement of trenches and drainage slots in swamps

Soils of weak foundations with a height of embankments up to 2 m are preliminarily drained or cut out. In bogs, partial or complete removal of peat from the base of the embankments is provided with backfilling of the trenches formed with soils suitable for the construction of embankments.

Trenches up to 4 m deep, as a rule, are developed by dragline excavators of the E-652 type with a TsNIIS bucket with a capacity of 0.8 m3.

In swamps with insufficient bearing capacity, it is advisable to carry out work on preparing the base in winter. In the summer, excavators move on portable boards. It is advisable to use excavators and bulldozers with widened tracks.

The peat, taken out of the trench by an excavator, is then moved by a bulldozer and leveled with a layer 0.5 m thick.If it is impossible to use a bulldozer due to insufficient bearing capacity of the surface of the swamp, the peat is thrown by an excavator or left unleveled in winter, leveled with a bulldozer in spring as it thaws.

The excavation of the trench with an excavator, depending on its width, is carried out with an end (Fig. 30, a) or side (Fig. 30, b) face for one or several penetrations.

The performance of the excavator in the end face is higher than in the side face.

The scheme for the development of a trench with an end face is used in cases that do not require a preliminary arrangement of drainage ditches.

According to the scheme of development with a sidewall, simultaneously with the development of the trench, it is possible to arrange a drainage ditch from the side of the excavator.

In both schemes, a dragline excavator of the E-652 type with a 13 m long boom arranges trenches up to 12 m wide and 2.5 m deep.

Development of trenches up to 25 m wide (Fig. 30, in) is carried out by sidewall with two penetrations. The excavator moves to the side of the trench, develops it half the width, and then, on the way back, develops the other half. At each pass of the excavator, it is possible to arrange a drainage ditch.

Trenches more than 25 m wide (Fig. 30, r) are arranged with three excavator penetrations. Simultaneously with the development of parts of the trench, drainage ditches can be arranged.

Trenches up to 1m deep in dry bogs with underlying dense soils with a width of the embankment base of more than 12m can be effectively developed with bulldozers. In this case, it is advisable to use bulldozers on a widened caterpillar track, as well as with shovel-type dumps.

Excavation of soil with bulldozers is performed by transverse penetrations. The peat is moved outside the placement of drainage ditches and leveled with a layer up to 0.5 m thick. Drainage ditches are arranged after peat extraction.

In swamps, to ensure vertical drainage of the base of embankments, as well as to accelerate the consolidation (hardening) of the base soils and increase their stability, longitudinal drainage cuts are sometimes arranged.

For the device of drainage slots, dragline excavators, backhoe excavators, as well as trench bucket excavators are used.

Draglines are used in the summer with a swamp depth of up to 4m. Trench bucket excavators are used in swamps with a depth of no more than 3 m both in summer and in winter, and in summer - on a widened caterpillar track, and in winter - with special replaceable working equipment designed for the development of frozen soils.

Backhoe excavators of the E-652 type can be used for the device of drainage slots in winter in swamps up to 4 m deep and with a frost penetration thickness of no more than 0.3 m.

The peat removed from the slot is moved with a bulldozer and leveled with a layer up to 0.5 m thick.

Following the fragment, the slots are covered with drainage soil (simultaneously with the construction of the embankment).

3. Preparation of foundations for embankments on mari, areas with underground ice, kurums and stone placers.

The preparation of the foundations for the embankment on the sails consists in ensuring the drainage of surface water, excluding the possibility of its accumulation at the foot of the slope, filling in low places, as well as lakes of thermokarst origin located near the embankment.

Backfilling is performed with local clay soil as the lower layer of the embankment is backfilled. Clay soil delivered by vehicles 0 \u003d dump trucks over the filled layer of the embankment is unloaded near the lowered meta and then pushed on by a bulldozer.

The top of the embankment is made in the form of a berm with a height of 0.2-0.3 m above the mari surface with a transverse slope of 0.02-0.04 to the side from the embankment.

As a rule, peat extraction is not provided within the marys.

In the permafrost zone, in areas of embankments with a height of up to 1 m, as well as in zero places, at the base of which waterlogged clayey soils lie, it is necessary to cut these soils to a depth of at least half the thickness of the Active layer, giving the bottom of the trench a longitudinal slope of at least 0.005.

Cutting out of soils in a thawed state is carried out by bulldozers. Frozen soils are preliminarily loosened with mounted rippers on bulldozers with a capacity of 300 liters. from. and more or in an explosive way. The loosened soil is moved by bulldozers into the shafts, from which it is immersed in dump trucks with an excavator and taken outside the embankment.

It is advisable to perform work on loosening permafrost soils at a high positive air temperature with a certain interval (in time) between loosening of individual soil layers. During the time between cleaning the loosened soil layer and loosening the next layer, the strength of the frozen soil decreases and its loosening requires less effort.

In the presence of subsidence foundations on areas of underground ice, both the preparatory period and during the erection of embankments, measures should be taken to preserve the natural conditions of the right-of-way to the maximum in order to prevent ice melting and related subsidence of embankments. This requires:

not to disturb the vegetation and moss cover at the base of the embankments and in the right-of-way;

felling trees in the minimum required amount;

prevent the drainage of the wetland and the device of longitudinal and transverse cuts in the base and at the foot of the embankment slope;

erect the embankments after the freezing of the active layer and before the onset of positive temperatures, pour it to a height of at least 1.2 m;

systematically remove snow from the entire area of \u200b\u200bthe base, which contributes to an increase in the depth of freezing of the base soil;

to allocate areas with underground ice to the restricted area and during construction and operation to prevent off-road traffic in this area, the construction of various structures, haymaking, etc.

In the areas of underground ice occurrence directly under the active layer, in some cases, it is envisaged to completely or partially remove this ice from the base of the embankments to a certain width. When the ice is completely removed, the trench is filled with drainage soil, and when the ice is partially removed, with clay soil. In the latter case, the thickness of the filled soil together with the embankment above the remaining ice should be at least 4 m. The slope of the trench is given a slope of 1: 0.2.

The process of removing soil from the active layer is indicated above. The ice is loosened in an explosive way, and individual layers and ice lenses are loosened with mounted rippers on 300 hp bulldozers. from. and more. The loosened ice is bulldozed into the shafts and loaded into dump trucks with an excavator. In winter, loosening of the soil of the active layer and ice by blasting should be done simultaneously.

Backfilling of the trench is carried out with the delivery of soil by dump trucks. In the summertime, the first layer of soil must be poured onto the surface of the ice or permafrost soil of the trench without driving dump trucks. For this, the soil unloaded by dump trucks is pushed forward with a bulldozer. Dump trucks are deployed for unloading on previously planned ground near the unloading point. The dumped soil is compacted layer by layer with soil compactors to the established density norm.

Construction of subgrade in highly rugged and mountainous terrain

Experimental work on the comprehensive mechanization of the construction of the roadbed was carried out by DORNII not only in flat and slightly rugged areas, but also in mountainous and highly rugged terrain.

The relief of the area where the work was carried out has a typical mountainous character, since the roads in it are designed mainly along steep slopes and ravines with serpentines, partly with retaining walls and with the use of drilling and blasting operations in some places.

Soil conditions in this area are characterized by a predominance of highly gravelly soils of categories III and IV, interspersed with individual areas of rock (limestone). The conditions for mechanization of earthworks in this area differ sharply from the usual conditions of flat and sparsely rugged terrain; the use of grader-elevators in these conditions is completely excluded, and the use of graders and motor graders is possible only in the most limited size for finishing work. The main machines suitable for work in mountainous conditions are: an excavator working with a front shovel without transport, a bulldozer and a scraper. The main type of roadbed in mountainous areas is a semi-embankment-floor near an excavation on slopes, often cut by ravines, in which artificial structures (pipes) are located with approaches in the form of relatively high and small embankments. Thus, the entire complex of work on the construction of the roadbed in these conditions consists of:
a) development of relatively gentle slopes in the gyulunasp-semi-excavation,
b) development of steep slopes,
c) construction of embankments in ravines for approaches to artificial structures.

In the construction area, this complex of works was complicated by the fact that all slopes were covered with dense deciduous forest.

Figure: 25. Scheme of felling timber with uprooting using a tension rope: 1-tractor, 2 - rope Felling timber from below

The use of excavators and bulldozers for slope work allows in many cases to get rid of a number of the most difficult preparatory work - uprooting stumps and combing out the root system from the upper layers of the road lane soil. Mandatory in all cases of construction of a canvas in mountainous terrain in the presence of a forest is the work of felling the forest and clearing the strip from bushes. Forest felling can be done simultaneously with uprooting, which is quite cost-effective in mountainous conditions. Terrain conditions with slopes with a steepness of 35 ° and more often do not allow the delivery of mechanization equipment directly to the route of the road under construction and force them to be placed below or above the road route on the existing temporary roads.

Let us examine these cases.

When the temporary road is located below the main road route (Fig. 25), it is advantageous to carry out felling together with uprooting, grabbing 10-15 trees simultaneously with a gripping rope, as shown in Fig. 26. In this case, after the felling of the forest from the root, no more preparatory work is required, since the logs of the felled trees are removed from the road lane in one step with felling and uprooting. When the temporary access road is located above the route (Fig. 26), it is impractical and very difficult to make timber felling with a straight cable upward. In such cases, the use of a block and an anchor stump located below the route is required, as indicated in Fig. 26. As in the first case, uprooting with simultaneous felling is more profitable here, since it requires only a tractor and a cable. A separate felling of the forest with electric saws, obviously, in these cases from the organizational side will be unprofitable, since it will require, on the one hand, the delivery of the power plant and saws to the work site, and on the other hand, will cause the need for an extra operation to clear the felled trees from the road strip, which in conditions mountainous terrain will create additional organizational difficulties. With gentle slopes, you can also use the above method of simultaneous felling and uprooting of the forest. Separate felling with saws can only be profitable when the growing forest consists of such large and thick trees that it will be difficult to remove them with a tractor.

Figure: 26. Scheme of felling wood with uprooting using a tension cable:
1 - tractor; 2- rope, 3 - block, 4 - anchor Felling timber from above

After clearing the dumped tree trunks from the production strip, you can begin to carry out the main excavation work. The development of gentle slopes with a steepness of up to 20 ° should be carried out mainly by bulldozers, since the use of excavators for it is unprofitable, because the latter will have to work mainly in low-height faces, which will reduce their production. The development of gentle slopes in the presence of rotary-type bulldozers can be carried out according to two fundamentally different basic work schemes.

The first scheme can be used with rotary bulldozers D-161 or D-149. It consists in the preliminary development of the slope layer by layer with a gradual movement of soil from the excavation to the embankment.

Subsequent passes cut with the right edge of the knife 30-50 cm from the line of each previous cutting. After 3-4 cuts, a mass of soil is formed, sufficient for a full-fledged passage along the movement of soil into the embankment without cutting. When designing each gouge layer, the first pass is usually not entirely complete.

The length of the processed section should be as large as possible in order to reduce the number of knife permutations during the return stroke. On average, each permutation takes about 1 minute.

This scheme has a number of significant disadvantages, which are as follows.
1. The scheme can be carried out only with rotary bulldozers. It is impossible to work with ordinary bulldozers according to this scheme.
2. The scheme requires repeated movement of the soil before laying in place in several passes. As a result of this scheme, each soil particle moves not only in the transverse, but also in the longitudinal direction. therefore design features bulldozers are used insufficiently expediently and their productivity is reduced.
3. At the beginning of work, the swivel bulldozer should work with a relatively large skew in relation to its longitudinal axis.

With a slope of more than 12-15%, such a skew can cause the tractor to derail its tracks. With a slope of 18%, skewed work becomes completely impossible due to the frequent descent of the tractor from the tracks.

Figure: 27. Development scheme of a slope with a slope of 20 ° into a half-fill-floor with a cut

4. The scheme requires frequent permutations of the blade angle (at each turn of the machine), which also affects the rational use of machines.

All these negative aspects of such a scheme of work make it possible to consider it inappropriate for widespread use in production, despite the fact that it is recommended by some authors.

The second scheme is applicable for the development of slopes with a steepness of up to 20 and even 25 ° (with an experienced operator) and consists in the fact that the development of the slope is carried out from the very first pass by transversely moving the soil with a bulldozer. The order of the development of the slope according to this scheme is shown on a specific example.

After placing the bulldozer perpendicular to the axis of the road, so that its knife is located 5 m from the transition point of the half-cut into the half-fill, we will make the first cut. Moving the bulldozer another 5 m, we will make the second cutting, which, together with the first in this case, will cover the entire surface of the slope to be developed into a half-cut.

The next (3,4 and 5) cuts will be performed in the same order. Obviously, the gouging marked in Fig. 27 No. 6, it is impossible to do it with a bulldozer, since a steep step has formed between the surface of the slope outside the half-cut and the surface of the soil in the half-cut after the first cutting. Therefore, cutting the soil in sections 6, 8, 10, etc. will have to be done with a grip angle of 67 ° with the left end of the knife or with a motor grader. Thus, the final development of the slope for the side ditch can be done with the joint operation of the bulldozer and only partially of the rotary bulldozer and the motor grader; the device of the ditch is performed by a number of additional passes of the motor grader in the process of finishing the roughly finished subgrade. This scheme is devoid of most of the disadvantages of the first scheme and can be recommended for widespread use.

If the balance of earth masses allows the development of a slope with a shallower slope of a semi-cut (up to 25 °), the scheme can be significantly simplified and all the main work can be done with a bulldozer without the participation of more complex machines such as D-149 or D-161.

In many cases, the development of reserves for the construction of approaches to artificial structures on slope sections of the Road in the places where it intersects with ravines is difficult, and it becomes necessary to prepare reserves in the course of the development of slopes. As a particular solution to this problem, a method of developing a slope with a widened ditch used as a reserve for filling pipes in ravines can be proposed.

In case of slopes overgrown with forest, the first passes of the bulldozer near the felling of the forest are made specifically for the purpose of uprooting the remaining stumps and harvesting the upper vegetation cover. Thus, when developing gentle slopes, a set of machines should be used as part of tractors for uprooting, bulldozers, a scraper, a D-162 ripper (for loosening dense soils before scraper work) and a motor grader for finishing work.

The development of steep slopes cannot be done with bulldozers alone, since bulldozers cannot work on large slopes either in the direction of the slope, and even more so, in the direction along the slope due to the inevitable derailing of the tractors from the tracks.

Of the available machines, the most suitable for the development of steep slopes are excavators working with a front shovel with a bucket capacity of 0.5 to 1.0 m3. In the pilot works in 1948, the development of steep slopes was carried out mainly by excavators with a bucket capacity of 0.5 m3. Excavators with a bucket capacity of 1 m3 can operate not only in soils of III, IV and V categories, but also in previously loosened soils of the highest category. The performance of these excavators is almost twice that of excavators with a bucket with a capacity of 0.5 m3, but their lower mobility is both construction site, and when transferring from object to object, greatly reduces the effectiveness of their use in linear road works.

The development of steep slopes cannot be completed by excavators. In the best case, only 50-60% of the volume of earthworks on the slope is put into place by an excavator, the rest of the work must be done by bulldozers or their varieties (D-149 and D-161), and partially by other machines. Thus, in the development of steep slopes, even more than in other terrain conditions, the complex work of a number of machines that make up the mechanized link is required. The development of the slope begins with the preparation of the site, from which the pioneer trench begins, necessary for the excavator to enter the mark of the future roadbed (Fig. 28).

Figure: 28. The beginning of the development of the pioneer trench with an excavator with a bucket of 0.5 m3

The pioneer trench is usually cut with a rise of up to 10-12%; it is developed with a straight shovel to the width necessary for the excavator to pass, that is, by 2.5-3.5 m. After the excavator reaches the level of the subgrade, it must begin the development of the main trench, depositing soil from the lower side of the slope. The width of the trench being developed should not exceed 4.5-5 m in order to increase the excavator output along the length of the road. On experimental work in 1948, in some cases, the Stakhanovites-excavators (comrades Efimenko and Gavryushin) achieved production up to 100 linear meters. m per working day with a productivity of up to 500 m3 per shift, which was about 200% of the norm. After the excavator, the development of the shaft dumped by it was carried out by bulldozers, and the development of the latter for leveling the shaft and expanding the trench made by the excavator was several times higher per linear meter. m excavator output. Thus, in order to more evenly load the machines participating in the slope development squad, it is necessary to strive to reduce the width of the excavator trench in order to increase its production along the length of the road and at the same time to load the bulldozers more. Experience has shown that one bulldozer can easily service the work of 2-3 excavators, even with a certain amount of time for independent work on the development of less steep slope sections.

With a slope of less than 30 °, the development of a slope in this way is possible with the construction of a subgrade in a semi-fill-semi-excavation without a retaining wall, but with the obligatory device of at least one ledge to stop the soil of a semi-fill. In the experimental work in 1948, the ledges were made manually, which, of course, should not be allowed in the future with the comprehensive mechanization of work. It must be borne in mind that the benches can also be made mechanically using small excavators with a bucket capacity of 0.25 m3. In fig. 29 shows the location of the benches: the main one - for the road bed and the auxiliary one, produced by a small excavator, - to stop the embankment slope.

With slopes steeper than 33 °, a semi-fill-semi-excavation device without retaining walls is impossible if it is required to withstand a half-fill slope.

If the device of the retaining wall, according to calculations, turns out to be not economical, and if we take into account that when determining the techno-economic indicators of the device of the retaining wall, it is necessary to reckon with a decrease in the degree of mechanization and production per worker in physical terms, then the development of the slope should be carried out without a half-fill, so that the entire shelf the road bed was located on the mainland in a recess (Fig. 30). In this case, all the soil produced by the excavator and after it by the bulldozer will go down the slope of the slope for ejection without registering it into a cavalier.

Figure: 29. Layout of ledges for abutting the soil during sloping work

It is necessary to make a reservation that in the construction of roads in mountains made of massive rock, in many cases the construction of retaining walls can be much more profitable than the expansion of excavations, since work in dense rocky soils requires a significant amount of relatively expensive and labor-intensive drilling and blasting operations. Per last years In the practice of the Ministry of Railways and other departments, mass explosions were often used to eject excavations and semi-excavations. Since these works are of a specific nature and in road conditions require special equipment, specialists, explosives, etc., this issue is not addressed in this work, especially since a fairly extensive literature is devoted to drilling and blasting operations in the construction of communication lines.

Figure: 30. Cross-section of the road on the slope in the cut

Figure: 31. Development of a trench for lowering an excavator into a ravine

Let us now turn to the question of arranging ravine crossings on a mountain road traced along the slopes of steep slopes. It has already been mentioned that in many cases the establishment of special reserves for the construction of these embankments is hampered by local conditions. In particular, the impossibility of laying separate reserves took place at almost all intersections of ravines along the route of the mountain road, which was being built in 1948.

The development of slopes at the approaches of the road route to the ravine can be organized in such a way as to create a reserve of soil on the road route itself so that in the future it can be fed into the embankment with scrapers with a longitudinal carriage. This can be achieved by developing a slope at the approach to the ravine at elevations higher than for the projected roadbed.

Having determined in advance, by appropriate calculation, the volume of soil required for the formation of the embankment, the development of the slope when approaching the ravine should, with a certain calculation of the place, be carried out above the design mark until the descent into the ravine. Approaching the descent, a pioneer trench should be developed for lowering the excavator into the ravine and crossing it downward (Fig. 31). On the other side of the ravine, the beginning of the development of the slope also begins at a higher elevation. In cross-section, the ratio of the design cross-section of the road and that actually developed by the excavator when approaching the ravine is shown in Fig. 32.

Figure: 32. Scheme of the ratio of the design diameter of the road and the diameter actually developed by the excavator when approaching the ravine: 1 - the shaft of soil, developed by the bulldozer under the slope, 2 - full-fill, 3 - reserve for the scraper, h - the height of the trench, I - slope of the excavator trench

All soil, not removed by an excavator in height with this method of slope development, is easily fed into the embankment by a bulldozer and a scraper (Fig. 33). The bulldozer feeds a shaft of soil, developed by the excavator, down into the ravine and softens the descent to the limits at which the scraper can be turned on.

The work of bulldozers in the development of steep slopes is carried out according to schemes that are somewhat different from those used in flat and slightly rugged terrain. It consists in leveling relatively high shafts of soil previously developed by an excavator, in preparing the front for the work of scrapers and, where possible, sites for installing excavators in the face.

The most common operation carried out by bulldozers in the development of steep slopes is moving down a slope and leveling the shafts of soil poured by an excavator to expand the breakdown of that shelf to the width of the roadbed required by the project.

Figure: 33. Scraper excavation of soil shafts dumped by an excavator

It can be seen from this table that with slopes up to 12 °, the excavator puts in place only about 10% of the soil it produces. Thus, with slopes with a low slope, up to 90% of the excavator's output requires secondary processing, which indicates the obvious disadvantage of using excavators when developing gentle slopes.

At slopes of 24 ° and higher, the excavator puts in place already about 30-35% of the soil it has worked out. The cross-sectional area of \u200b\u200bthe trench he is developing, depending on the steepness of the slope, ranges from 8.5 to 20-plus m2, and the dimensions of the shaft to be further processed by a bulldozer reach 17 m3 per linear meter. m of the road. To complete the work done by the excavator in 1 hour of work, it is required to spend from 0.17 to 0.27 car-hours of the bulldozer's work.

Therefore, on average, one bulldozer can serve the work of 4 excavators. Obviously, with an increase in the bucket capacity of an excavator to 1 m3, the number of excavators serviced by one bulldozer decreases on average to 2. In addition, these data also indicate that a decrease in the section of the trench produced by the excavator will increase the rate of construction of the roadbed in linear meters. m and will load bulldozers more fully.

The shafts filled with an excavator can be developed with the D-157 or D-161 bulldozers. The swivel bulldozer is more efficient in working conditions more convenient, since its operations require a smaller trench width (for the operation of the D-157 bulldozer, it is necessary to provide a trench width of about 6 m, and for the D-161, 4.5 m is enough). The bulldozer starts mining with the knife raised and pushes the soil forward (fig. 34). At this moment, the soil above the bulldozer blade falls down. It turns out the development of the shaft by digging. A bulldozer knife is lowered onto the ground that has fallen down. In one or two passes, the soil is dumped down a slope and the excavator trench expands. From table. 18 shows how great the performance of bulldozers is at this job. To develop a shaft with a volume of 57.4 m3 in a loose body (with an average loosening coefficient of 1.3), only 0.23 machine-hours are required. of work of the bulldozer, i.e. the productivity of the bulldozer is about 140 m3 per hour of clean work, and for the development of a shaft with a volume of 50.6 m3 - 0.2 machine-hours, i.e., the productivity in this case will be 115 m3 / hour. On average, the performance of the D-157 and D-161 bulldozers when processing shafts downhill will be about 1200 m3 per shift.

In cases where it is required to dump the shaft not down a slope, but to move it along the slope to backfill any lowering, the development of the shaft should be carried out in two steps: the first step, the bulldozer, rising from the end side to the crest of the shaft, slightly smoothes and expands the upper part shaft so that a tractor with a scraper can subsequently climb onto it for further longitudinal transport of the soil.

Therefore, the task of the bulldozer operator includes not only smoothing the crest of the shaft with its expansion on top of at least 3 m, but also laying the entry and exit from the shaft to create a convenient front for the scraper.

In cases where the length of the longitudinal movement of the soil is small, the bulldozer can independently carry out the work of moving the soil into place. With high and relatively narrow shafts, this work is done by digging with the installation of a knife during the first pass approximately in the middle of the shaft height - to crumble the soil, and then the knife is buried in the ground by half or a third of its length, to the entire height of the dump and moves with the ground along the axis of the road ...

Figure: 34. Movement of shafts filled with an excavator or bulldozers

The performance of the bulldozer with such a design of the shafts is also very high and with a travel distance of 30-40 m it is from 800 to 1000 m3 per shift.

Thus, the composition of the detachment for the construction of the road in the mountainous area was determined: the main vehicle of this detachment is an excavator. When working on steep slopes, it is better to work with one excavator with a bucket capacity of 1 m3 on the main shelf and one small excavator with a bucket capacity of 0.25 m3, included in the detachment specifically for making benches.

To service such a small detachment, only one bulldozer needs to be assigned, but it will not be fully loaded either.

Therefore, it is advisable to make a detachment of two excavator links (4 excavators), serviced by one bulldozer and one scraper.

Such a detachment should include a D-162 ripper (to ensure the work of scrapers in heavy stony soils) and a supply of rope for felling wood.

The front of such a detachment should be at least 1-1.5 km, and the excavator links should work with a gap of at least 1 km between themselves in order to avoid frequent transfer of these heavy machines.

TO Category: - Mechanization of earthworks