A bulldozer is an earth-moving and transport machine that performs development, transport, backfilling and leveling of soil (Fig. 2.42). However, when a bulldozer operates, unlike a scraper, the developed soil does not move in a bucket, but is dragged along the ground, pushed by the working tool - the knife. The volume of pushed soil (drawing prism) depends on the size of the knife, which, in turn, determines the required energy (motor power of the base machine).
1. Type of product: site planning, construction of shallow (up to 3 m) pits, low (up to 3 m) embankments, completion of soil in the pit after the excavator, backfilling of trenches and pit cavities. The latter processes are carried out mainly using bulldozers.
2. Composition of the process: soil cutting, transportation (dragging) of soil, backfilling, leveling, return (idling) (Fig. 2.43).
3. Entry to the process is general (see page 29).
4. Resources.
4.1. Materials – soils of groups I–II of natural composition; loosened soils of groups III–IV.
4.2. Equipment: bulldozers. They are distinguished by their base: tracked - have a large traction force; wheeled ones are more mobile and do not require special transport for delivery to the site. The main technological parameters of a bulldozer are the dimensions of the knife (blade), which determine its performance.
The knife can be fixed rigidly - uncontrollable; it is possible to have a knife control system (rotation at a certain angle) in the horizontal and vertical plane (Fig. 2.44).
5. Process technology.
The bulldozer operation pattern can be: shuttle, shuttle with offset, zigzag, side penetration (for backfilling) (Fig. 2.45). The rational range of soil transport is 10–40 m, in some cases up to 70 m. When using special technologies: trenching, frontal movement - up to 100 m.
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| Rice. 2.44. Development and leveling of soil with a bulldozer: a – moving the blade in a vertical plane; b – installation of the blade in plan at an angle to the longitudinal axis of the bulldozer; c – the same, at an angle to the horizontal plane; d – slope planning with a bulldozer equipped with a slope blade; 1 – tractor; 2 - hydraulic cylinder or rope pulley; 3 – blade; 4 – slope leveler blade |
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The development of pits is carried out on one side (Fig. 2.46, a), and for large sizes, in order to reduce the hauling distance, the development is carried out from the center on two sides (Fig. 2.46, b; 2.47).
Soil is poured into the embankment in layers, alternating with compaction; the thickness of the layer is set by the power of the compaction mechanism and is 0.3–1.0 m. If necessary, intermediate moistening of the soil of each layer is carried out (Fig. 2.47).
Backfilling of trenches and pit cavities is also carried out in layers, alternating between filling the layer and compacting it. After filling, the soil layer is wetted for effective compaction.
When backfilling pipelines, two manual operations are performed before the bulldozer operates: adding soil (tamping) under the pipe and backfilling the pipe with a 30–50 cm layer of soil. After manual operations, the bulldozer begins to “throw” soil into the trench. When backfilling collectors, reinforced concrete trays of heating mains, etc. backfilling is carried out alternately: first on one side to a height of 0.5 m, then on the other to a height of 1.0 m and further, alternating 1.0 m at a time. Backfilling of the retaining wall sinuses is carried out in horizontal layers along the entire length of the wall or its section.
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| Rice. 2.50. Carrying out backfilling using a bulldozer with an inclined blade: 1 – dumping soil to fill the trench; 2 – backfilling of soil manually; 3 – direction of movement of bulldozer 1; 2; …5 |
All backfills within the city limits must be backfilled only with sand as soil with minimal settlement.
To increase the performance of the bulldozer, the following schemes are used:
Cutting and dragging soil when the bulldozer moves downhill. Increased productivity by 3–5% (Fig. 2.51);
To hold a large amount of soil pushed by a bulldozer, openers are installed on the knife. Increased productivity by 7–15% (Fig. 2.51);
Frontal movement (work) of two or three bulldozers. This allows you to significantly increase the volume of the drawing prism and increase productivity by 30–70%. However, this requires highly qualified drivers to ensure the synchronous operation of two or three bulldozers (Fig. 2.52);
Trenching. Here the walls of the trench hold the soil on the dump, and the bulldozer transports the maximum volume of soil possible for a given engine power. Walls can form naturally during bulldozer operation due to soil lost on the sides of the dump (Fig. 2.53), as well as from undeveloped soil during parallel excavation of two or three bulldozers with a certain distance between them.
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At a construction site, a bulldozer carries out the planning of roads, paths for tower cranes, the leveling of soil and sand dumped by dump trucks, as well as the construction of ramps into pits, etc.
Technology assessment. Based on the type of earthwork being constructed, the availability of specific equipment and the specified hauling distance, an approximate estimate of the costs of excavating soil can be made from the table. 2.3.
Source: Technology of construction processes. Snarsky V.I.
Schemes for performing work with bulldozers
There are three main schemes for developing and moving soil with bulldozers: straight, lateral and stepped.
The direct scheme is used when digging trenches and excavations, the width of which is slightly greater than the width of the bulldozer blade; when constructing entrances, when dumping soil in one place is allowed. Working according to this scheme, the bulldozer, when developing and moving soil, moves in a straight line, making a reciprocating motion without turning. This pattern of movement of bulldozers is often called pendulum. When moving forward, the bulldozer cuts the soil certain area path, and then transports it to the dump site (working stroke). Then it returns to the place where it started cutting the soil, moving in reverse (idling). The number of working and idling strokes of the bulldozer depends on the design depth of the excavation and the thickness of the soil chips cut in one pass.
The lateral operating pattern of the bulldozer is used when moving previously developed soil from dumps or bulk materials (sand, gravel, etc.) from bunkers, when developing light soils cut off in thick layers, as well as when working on slopes. In this case, the excavated soil is located on the side of the path along which the bulldozer transports it to the dumping site. The bulldozer grabs the soil with a blade, makes a turning movement, moving the soil onto the transport path, and then transports it to the dumping site. Only a qualified bulldozer operator can work in a lateral manner, since with insufficient experience in operating a bulldozer, a significant part of the soil can be lost while turning the bulldozer.
A stepwise scheme for the development and movement of soil is used mainly when constructing embankments, performing stripping operations and vertical planning of areas, when it is possible to pour the excavated soil over the entire width of the excavation. Working according to this scheme, the bulldozer develops the soil with parallel penetrations. Having moved the soil from one tunnel, the bulldozer makes an idling move at an angle to the axis of the working stroke and begins to develop and move the soil in a nearby tunnel (Fig. 96).
Rice. 96. Scheme of constructing an embankment with a bulldozer
1 - direction of the working stroke of the bulldozer; 2 - alignment pegs; 3 - high-altitude poles; 4 - filled layers of soil; 5 - direction of idling of the bulldozer; 6 - direction of the bulldozer's working stroke
The considered methods of developing and moving soil are used to a greater or lesser extent in almost all earthworks carried out by bulldozers. Below are specific examples of organizing bulldozer work on various earthen structures.
When performing stripping operations with soil dumping into a previously mined-out space, soil development is carried out with intersecting penetrations inclined towards the excavation under coal 10... 12°. Soil development begins in areas located in the immediate vicinity of the upper edge of the slope of the old excavation. In this case, the thickness of the cut soil layer is increased as the bulldozer approaches the excavation, so that it is maximum at its slope.
Vertical planning of areas using bulldozers is carried out after breaking down the entire area, indicating the depth of soil removal in high areas and the height of its filling in excavations. The soil is developed by parallel excavations. In this case, it is advisable to use a combined scheme for developing and moving soil, combining direct and stepped schemes.
The construction of embankments by bulldozers without the use of other machines (rollers, watering machines) is allowed only in cases where technical specifications The work does not require soil compaction and local data allows the use of soil from reserves.
Depending on the width of the embankment, soil development is carried out in one- or two-sided lateral reserves. An embankment is being erected in the next technological sequence. Before starting work, a geodetic breakdown of the embankment and lateral reserves is carried out, the purpose of which is to outline the axis and boundaries of the base of the embankment, the boundaries of the berm and reserves. Reserves are laid mainly on the upland side of the embankment with a transverse two-sided bottom slope of 0.02 towards the middle of the reserve. The longitudinal slope of the reserve bottom must be no less than 0.002 and no more than 0.008. For ease of work, the embankment is filled with grabs 50...100 m long.
Soil development begins from the field edge of the reserve. Moving at first speed, the bulldozer cuts off the soil in layers up to 30 cm and moves it towards the embankment. When approaching the berm, the bulldozer blade is gradually raised so as not to cut off the soil on the berm. The soil is placed into the body of the embankment using rollers, placing them along the width of the embankment. The bulldozer is idling in reserve at maximum reverse speed.
The soil from each excavation in reserve is placed in the body of the embankment, placing it along the width of the embankment, after which the bulldozer begins to develop the soil at the next excavation with rollers. After filling the first layer of the embankment along the entire length of the grapple, the bulldozer rises onto the embankment and, moving along the structure, levels the soil laid with rollers, simultaneously compacting it with caterpillars. The bulldozer fills subsequent layers of the embankment in the same sequence. Having finished filling the embankment to a given height, the bulldozer levels the top layer of soil, plans berms and the bottom of the reserve, bringing the longitudinal and transverse slopes to the design levels.
Filling of embankments with a height of 1.5...2 m can be done without layer-by-layer leveling of the poured soil immediately to its full height. In this case, the working elevation of the embankment should be increased against the design level by 10... 15%, since the embankment will settle for a long time after construction.
When constructing a roadway on slopes, soil is developed and moved into a semi-embankment using longitudinal and transverse moves of a bulldozer. On slopes with a transverse slope of 8...10°, it is advisable to develop the soil using longitudinal moves. In this case, the bulldozer moves the soil into shafts located across the entire width of the half-excavation. Subsequently, the bulldozer transports soil from the shafts to the half-embankment, moving at an angle to the axis of the Road surface under construction. On slopes with a transverse slope of 12...20°, soil development is carried out by transverse penetrations, on which the bulldozer moves perpendicular to the axis of the roadbed under construction. This allows you to increase the productivity of the bulldozer by increasing the thickness of the cut soil layer, since the bulk of the soil moves downhill.
Before moving the soil into the half-embankment, the surface of the slope, which is the base for the half-embankment, is loosened or ledges are cut with a bulldozer. To protect the road surface from the influence of surface water, a drainage ditch is torn off from the upland side using a ditch digger or a bulldozer, to the blade of which a special attachment is attached.
Backfilling of the trench with a bulldozer is carried out with soil from a dump located along the trench in the following technological sequence. After laying a pipeline, cable or other structure, it is simultaneously backfilled on both sides manually (so as not to damage or displace the backfilled pipeline or structure) to a height of 0.25 ... 0.3 m above the top of the structure. Further backfilling of the trench is carried out by a bulldozer, moving in criss-cross transverse moves.
The dump area is divided into separate sections, the bulldozer approaches the soil dump at a certain angle, picks up the soil in section I and moves it into the trench. After this, he moves soil from section II into the trench using transverse penetrations, then oblique penetrations from section III, transverse ones from section IV, etc. A similar pattern of bulldozer movement is used when filling the foundations of buildings. With this alternation of directions of movement of the bulldozer, the path of its movement with soil is reduced and the conditions for collecting soil are improved.
Backfilling of an artificial structure, the design of which does not require manual backfilling (reinforced concrete collectors, tunnels, pipes) large diameter etc.), are produced in the following order. First, the structure is sprinkled on one side to a height of up to 0.5, then it is sprinkled to a height of up to 1 m on the other side with soil brought by dump trucks. The final backfilling of the structure to its full height (after it has been covered on both sides) is carried out as indicated above. Compliance with this sequence of backfilling is necessary, since with one-sided backfilling, deformation of the structure is possible.
When clearing slopes with bulldozers, soil dumps are placed primarily along the lower edge of the slope being cleared. This allows soil to be moved from top to bottom. With the help of bulldozers, slopes whose steepness does not exceed 1:2.5 are cleared.
In some cases, it is allowed to clear slopes by moving soil up the slope. Organizing work according to this scheme is advisable in areas where the bulk of work on clearing slopes is carried out by excavators or other machines, and bulldozers only clean and level the slopes.
TO category: - Mechanization of earthworks
The exact price for filling trenches and pits with a bulldozer is determined taking into account several factors. First of all, these include the volume of work to be done and the equipment used. It is often necessary to organize additional delivery of soil or sand for backfilling. In such a situation, expenses will be required for the use of dump trucks, the most popular models of which are deservedly considered Scania And domestic KAMAZ trucks.
Obviously, filling trenches with sand allows for better quality work. In addition, this material, even without compaction, practically does not sag, which allows, if necessary, landscaping without fear of the subsequent formation of pits on the surface. When using soil, it needs additional compaction, for which various vibration compactors, produced by the most famous brand of such equipment Wacker Neuson.
Hire a bulldozer to fill the trench
Our company offers simple and quick way hire the equipment necessary to complete the work. At the same time, a competent manager will help you choose a model so that filling the trench sinuses with an excavator or bulldozer can be done not only quickly and efficiently, but also with minimal financial costs. An important advantage of working with us is the use of only serviceable equipment produced no earlier than 2011.
Backfilling and soil compaction in cramped conditions are largely determined by the technological specifics of the work: the limited scope of work and the peculiarities of the geometric elements of the earthen structure, which practically makes it difficult and sometimes excludes the possibility of using ordinary cars. Most often, soils are subject to compaction in the cavities of foundations, pipelines, sewers, manholes, foundations under floors inside buildings, at the intersections of various types of communications (Fig. 4.13).
The conditions for backfilling the sinuses of foundations, especially during the construction of industrial facilities with developed underground facilities, are distinguished by significant diversity. The external cavities of pits, which are mostly wedge-shaped, in combination with the cavities between underground structures and foundations inside buildings and structures, often form a system of closed cavities and corridors with limited clear dimensions and present a serious difficulty when performing backfilling.
For backfilling small objects are handed over entirely, and large ones - in large parts after complete completion of work on underground structures or after completion of work on a dedicated tier.
The most typical examples of backfilling and soil compaction in cramped conditions are discussed below.
Compaction of soils in the cavities of foundations under columns. When the column spacing is 6 m or more, when installed foundations do not interfere with the movement of vehicles; soil is filled from the farthest point of the working map “towards you”. In this case, dump trucks move along a base on which a layer of soil is laid.
The dump truck unloading scheme is set depending on the distance between the axes of the columns. The soil is filled in strips along the spans between the columns in order to reduce the labor intensity of layer-by-layer leveling of the soil.
When the column spacing is 6 m and the location of the foundations impedes the movement of dump trucks, soil is poured into the lower layers of backfill with the dump trucks driving over the dumped soil, covering the protruding parts of the foundations with a layer of at least 0.3 m thick to avoid their damage.
The dump truck is selected taking into account the dozer blade and maneuvering conditions at the work site.
Layer-by-layer leveling of soil is carried out by bulldozers D-159B, D-271M, etc., and in less accessible places - by a small-sized bulldozer based on the T-54V tractor and an M-B-4 micro-buldozer. When the width of the gap between the foundations of the columns is less than 0.8 m, where the use of bulldozers is impossible, the soil is leveled manually.
The work is carried out in two stages: Stage I - soil compaction between the foundations of the columns; Stage II - compaction of the soil above the foundations of the columns.
Soil compaction between column foundations is carried out in more cramped conditions than above foundations. Compaction of soil with heavy tampers, which have a large dynamic effect on the compacted soil, is not allowed in this case in order to avoid horizontal displacement of the columns.
To compact the soil in the area adjacent to free-standing foundations or other underground structures, rolling, vibratory compaction or a combined effect on the soil (vibratory rolling, vibratory compaction with a weight) is performed. To do this, depending on the degree of cramped work conditions and the properties of the soil, the following are used: self-propelled rollers with smooth rollers with cam bands on them, vibratory rollers, self-propelled vibrating plates produced by the GDR (SVP type), hydromechanical vibration compactors, electric self-propelled vibratory rammers and electric rammers.
First of all, excavation of soil compactors should be carried out in the immediate vicinity of the foundations, then in the area between the foundations. After filling the foundations of the columns with soil, when there is a layer of soil of at least 0.3 m above the upper edge of the foundation, the work of stage II begins.
As an example in Fig. 4.14 shows the technology for performing work on soil compaction in a trench with a row separately standing foundations, installed in 12 m increments.
Before backfilling the trench begins, the following work must be completed: the construction of the foundations is completely completed and their design position is checked; waterproofing of foundations was made and checked; all auxiliary materials, equipment, and mechanisms were removed from the trench; acts were drawn up on hidden work and the customer’s permission for backfilling was obtained.
Backfilling is carried out with imported soil, which is delivered to the work site by dump trucks; backfilling and leveling of the soil, with the exception of the last layer, is carried out with a leveling excavator equipped with a boom extension and equipped with a loading bucket. The leveling excavator moves along the upper edge along the trench. Zones 40 cm wide around foundations and kneecaps, as well as “dead zones” that cannot be leveled by a leveling excavator, are leveled manually.
The last layer is filled and leveled with a bulldozer with a rotary blade.
Compaction of cohesive soil is provided by manual electric tampers, and of non-cohesive soil by self-propelled vibrating plates, with the lower layers being compacted by smaller vibrating plates, and the upper ones by larger ones. Soil compaction must begin in the areas around the foundations (pillars), and then in the area between the foundations (pillars). Each subsequent pass of the compaction machine must overlap the trace of the previous layer by 0.1-0.2 m. The thickness of the compacted layer depends on the type of soil and the type of compaction machine (varies from 0.2 to 0.6 m).
Soil compaction in pits with complex foundations and underground structures. When constructing objects with complex foundations and underground structures that form a system of closed cavities, dead ends and narrow passages in plan, the movement of large-sized machines through them is excluded. Backfilling of soil is carried out immediately after the construction of the underground part of a building or structure (stripping and waterproofing the surfaces of underground communications) before starting work on the above-ground part.
Soil delivered by dump trucks using an excavator equipped with a grab (or a conveyor system) is supplied to the working map within the area limited by underground structures. Depending on the nature and size of the sinus, leveling the soil is carried out with a small-sized bulldozer of the UZBT-54V type or an MB-4 micro-buldozer. Soil compaction is carried out using electric rammers or a suspended vibrating rammer PVT-3. For this purpose, vibratory pile drivers VP-1 or VPP-1 installed on a metal pallet can be used.
To compact soil in closed cavities, soil compactors suspended from a crane are more convenient, and when working in cavities connected by passages, self-moving vibrating plates and manual rammers are used.
To fill the sinuses that communicate with each other, the in-line method of performing work is used. In this case, the machines performing layer-by-layer laying of soil, after filling the soil layer in the area of operation of the feeding unit, move to the next working map, and their place is taken by soil-compacting machines.
When backfilling foundation cavities with different depths, work is first carried out within the area with lower elevations until the general level is reached, then work is carried out throughout the entire foundation pit.
As an example in Fig. Figure 4.15 shows the technology for backfilling, leveling and compacting soils in pits with complex foundations for technological equipment in an industrial building with a column spacing of 12 m.
The soil for backfilling is delivered by ZIL-MMZ-555 dump trucks and supplied by an excavator with a grab bucket with a capacity of 1 m3.
With a pit depth of 4 m, leveling the soil to the 2 m mark is carried out manually. From a mark of 2 m to ±0.0 m, the soil is leveled with a DZ-14A bulldozer (shaded area in Fig. 4.15), and in hard-to-reach places - manually. The soil is leveled manually also around structures within a radius of 40 cm. Compaction non-cohesive soil Group I is carried out with vibrating plates of the SVP type, cohesive soil of Group II is carried out with electric rammers of the IE type.
If available in the workshop being reconstructed overhead crane the latter can be equipped with a grab bucket for feeding soil into work area(Fig. 4.16). The soil is leveled with an MB-4 micro-buldozer or manually in narrow spaces between foundations and walls, followed by compaction with a vibratory rammer and electric rammers. -
Compaction of soils in narrow and deep cavities. Sinuses with a width of less than 1.4 m are usually considered narrow (the maximum size of the sinus that allows the operation of a small-sized bulldozer). A worker can work in sinuses with a width of 0.7 to 1.4 m; worker access is impossible with a width of less than 0.7 m.
The soil, delivered to the work site by dump trucks or loaders in the volume necessary for laying the compacted layer, is poured on the edge of the pit and then fed by an excavator, leveling excavator, or pushed into the bosom by a bulldozer (Fig. 4.17). The soil must be fed and pushed in a dispersed manner to reduce the amount of work involved in leveling and moving the soil at the bottom of the cavity.
Layer-by-layer compaction of the soil in the lower (narrowest) part of the sinus is carried out using suspended vibrating ramming plates PVT-3, VTM-2 or pile vibrating drivers on metal pallets suspended from a crane installed on the edge of the pit.
In the middle (wider) part of the sinus, BM-4 micro-buldozers and small-sized rollers are used to level and compact the soil in layers of a given thickness, which are fed into the sinus by a crane. Then, as the sinus expands (more than 1.4 m), a small-sized bulldozer based on the T-54V tractor is used.
Very narrow and cramped places, saturated with communications, when the possibility of using mechanization means for layer-by-layer compaction is excluded, should be covered with sandy soil. Backfilling with sand is carried out with accompanying abundant watering, creating the effect of hydro-washing. This method is also suitable for backfilling cramped areas when sand is the local soil and underground structures allow for strong moisture. This method is not applicable in winter conditions.
To compact backfills made of loess-like loam in the cavities of foundations more than 2 m thick, the deep method can be used. This method of compaction is based on the immersion of dies, which form wells with the displacement of soil radially to the sides; in this case, the soil is compacted around the well.