The smallest digging radius at a given depth (Ri) is determined depending on the development depth, position and angle of repose.
The greatest digging depth (Hk) is set to the level of the bucket teeth at the greatest inclination of the boom and depends on the amount of movement (a). The shallower the digging depth, the longer the travel length can be.
The radius of unloading of the bucket (Rp) is the distance from the axis of the excavator to the teeth of the bucket at the required height at the moment when it begins to pour out of it. For mechanical excavators with a bucket rigidly connected to the handle, unloading occurs when the handle is turned from the initial to the final unloading radius, and the location of the blade or vehicle body must be taken into account. For hydraulic excavators, bucket unloading is not related to the position of the boom and arm.
Bucket unloading height (hp) is a value that depends on Rp and the height of the vehicle body (or dump), taking into account the margin between them and the bottom point of the bucket at the time of unloading, equal to 0.1 m.
An excavator with dragline working equipment is used to develop soils of groups I-VI below the standing level when digging pits, trenches, canals, constructing embankments from reserves, extracting sand and gravel from under water with loading the soil into vehicles and working outwards (Fig. 4.5, G). The dragline bucket is suspended on two ropes (lifting and traction). The traction rope is used to move the bucket (drawing) when collecting soil, and the lifting rope is used to lift the bucket. The raised bucket is held in a horizontal position (inclination 10... 15° to the horizon towards the rear wall) by a traction rope. At the unloading site, the traction rope weakens and the bucket tips over.
Let's consider the main technological parameters of the dragline (Fig. 4.5, d). The radius of the overall installation (R0) is determined in the same way as for forward and reverse shovels.
The smallest digging radius at the parking level: R1 = Z0 + y/tg0 (assumed not less than Ro + 1m).
The largest dripping radius at the parking level: R2 = Rp + Hgtgβ.
The distance Hгtgβ is called the bucket throw value. The angle P is almost 7° on average.
The smallest digging radius at the level of the excavation bottom (R3) depends on the digging depth and on the position and magnitude of the excavation slope: R3 = R1 – H3/tg0.
The largest digging radius at the level of the bottom of the excavation (R4) depends on the position and length of the boom, as well as on the amount of cast:
R4 = R2 + 0.123H3.
The greatest working depth (Hmax) is the distance from the excavator parking level to the teeth of the bucket thrown down, with full use of the lengths of the traction and lifting ropes. Taking into account the need for horizontal movement of the bucket along the bottom of the excavation to move the excavator, the greatest development depth is calculated with the smallest amount of movement (for example, 1 m).
The smallest development depth (Hmin) is the depth at which a slope of length lн is formed, ensuring normal filling of the bucket with soil:
The angle of repose 6 depends on the soil group according to the complexity of development: for group I 9 = 45°, for groups II-III 0 = 38°, for groups IV-V 6 = 33°, for group VI 6 = 29°.
The length of the advance (a) depends on the development method (the width of the excavation and the location of the excavator) and the depth of the excavation. It should be such that from the new parking lot the excavator can excavate the most remote areas of the slope.
An excavator with working equipment, a grab, is used to develop soils of groups I-III, located below or above the level of the machine, when digging deep pits with vertical walls, trenches, extracting sand and gravel from under water, loading and unloading bulk materials, supplying soil during backfilling of trenches and pits. The grab is used on excavators with mechanical and hydraulic drive. In the first version, it is suspended on ropes to the dragline boom or, in the second, it has a flexible or rigid suspension to the handle. A grab with a rigid suspension consists of a stand with a cylinder and bucket jaws. Let's consider the main technological parameters of an excavator equipped with a grab (Fig. 4.5, f).
The radius of the overall installation of an excavator with a grab (Ro) is determined in the same way as for the excavators discussed above.
The smallest digging radius at the parking level (R1) depends on the maximum rotation angles of the boom and arm, as well as on the size of the grab bucket.
The largest digging radius at the parking level (R2) also depends on the linear dimensions of the elements of the working equipment.
The development depth (H3) for mechanically driven excavators is determined by the length of the lifting rope and the angle of inclination of the boom. For hydraulic excavators, the bucket is lowered when the boom is tilted and H3 mainly depends on the length of the stand and the working stroke of the hydraulic cylinder rod. Practically for mechanical excavators H3< 6 м, для гидравлических- H3<10 м.
Slaughter– an excavator workplace, which also includes a vehicle maneuvering area. There are frontal and side faces.
Frontal face(Fig. 7.6). In frontal mining, soil development is carried out in front and on both sides of the excavator in a strip determined by the operating parameters of the excavator and the position of the vehicles. The face parameters (width B and depth H) depend on the parameters of the excavator and the location of the vehicles.
When vehicles are located at the bottom of the excavation (at the excavator parking level), the face parameters also depend on the requirements for the excavation profile and the straightness of the slope. They are easy to determine if you know the parameters of the excavator and vehicles.
Rice. 7.6. Frontal face schemes
a) with unloading into a dump; b) with loading onto a vehicle above the parking level; c) with loading onto the vehicle at the parking level
If possible, excavation with a “wavy” slope
If it is necessary to accurately maintain the profile of the excavation and the straightness of the slope
(7.5)
lper = (0.6 ÷ 0.7)∙lх.р. (0.8 ÷ 1.2 m – for low-power excavators, 1.5 ÷ 2.0 m – for medium-power excavators, 4.0 ÷ 6.0 m – for high-power excavators).
When vehicles are located above the parking level (on the edge of the excavation), the parameters of the excavation depend on the conditions of loading soil onto the vehicle (one-sided or two-sided unloading) (Fig. 7.6b).
For one-sided unloading
Нз = Нв – htr. -a
where: Tue. – width of vehicles; C – distance from the edge of the slope to vehicles; htr. – height of the vehicle; a – reserve in the position of the bucket above the vehicle during the unloading period.
With 2-sided unloading
B = 2B1 £ 2Rp (7.7)
Side face(Fig. 7.7). The side face is used when developing soil on one side of the excavation axis and loading soil onto vehicles for large excavation sizes.
Rice. 7.7. Side face scheme
Face parameters:
Bmax = B1max + B2max Hp £ Hp.max
– when working with a flat slope.
B1max = Rp.max – when working with a wavy slope.
B2.max = Rv.max – 0.5 vtr – C – when the transport is located at the level of the boom rotation axis (b = 90°). (7.8)
В2.max = Rв.max Sinb - 0.5 vtr. – C – when the transport is located in front of the excavator. Usually bav. = 70 – 90°. (7.9)
Face width:
For fun = B1 + B2 – (Rp – Rmax) (7.10)
All designations are the same.
At significant depths and large dimensions of the excavation (H > Hp max), it is divided into tiers and separate strips - faces (Fig. 7.8). The excavator enters each tier through a passage pioneer trench, the depth of which is determined by the soil unloading conditions and the location of the transport.
Number of tiers: , (7.11) Number of full tapes: 
, (7.12)
where: H – total depth of the excavation; Нз – maximum face height; B is the width of the recess in each tier at the top; Вп – width of the first tape (pioneer trench); VL – width of one development strip; nл – number of full ribbons in one tier (rounded up to a higher number).
Rice. 7.8. Scheme for developing a large area pit
a) plan; b) cut
1 – pioneer trench; 2 – path of movement of the excavator; 3 – excavator
Approximate practical dimensions of face heights for straight shovels vary:
7.3. Technology for performing work with backhoe excavators
Excavator operation with straight shovel equipment
The working equipment of a straight shovel is used when excavating soil above the excavator parking level. An excavator equipped with a shovel is most often used when excavating soil with loading into vehicles. Work can also be done in a dump, but in this case it is more advisable to use a dragline, since its working dimensions are larger than those of a straight shovel.
Before starting work, you should carefully prepare the face. ‘Preparing the face consists of clearing its bottom from stones, uneven surfaces, scattered soil and foreign objects. After cleaning, the axes of the excavator are laid out and roads are prepared for transport.
Rice. 1. Loading soil into dump trucks using an excavator with a straight shovel during side mining
Working with a straight shovel when loading into vehicles can be done in two main ways:
a) side face, when transport routes are located on the side of the excavation;
b) a lot face, in which transport is fed from behind the excavator along the bottom of the excavation being formed.
Rice. 2. Frontal faces: a - with a penetration width of less than 1.5 R; b- with a penetration width of 1.5-1.9 R
The first method provides more high performance than the second, so it is used more often.
The most common type of side face of an excavator with a straight shovel is one in which work is carried out with loading soil into vehicles at the excavator parking level. In this figure (and further) R is the largest cutting radius in m, and Rcm is the largest cutting radius at the excavator parking level in m. Side faces are also used, in which the soil is loaded into a vehicle located slightly above the excavator parking level. Such models (E-258, E-505, OM-202, etc.). For example, when digging pits with a width of about 2.5 R, innovating excavator operators work by moving the excavator in a zigzag.
Rice. 3. Frontal face with unloading of soil into vehicles moving along the edge
Rice. 4. Widening of the frontal face when moving the excavator in a zigzag
Rice. 5. Widened three-stage transverse frontal face
Excavations up to (3.0 3.5) R wide in some cases can be developed using a three-stage transverse face.
Techniques for working with a straight shovel
To increase the productivity of the excavator, it is recommended to use the following operating techniques.
Before starting work, the excavator should be installed strictly horizontally in order to reduce wear on the ring gear and central axle. In this case, the tracks must rest on the ground along their entire length so that the machine is stable and does not tend to roll back during operation.
Rice. 6. Formation of a visor in the face when working with a straight shovel
The development of the face must begin from the side of the bucket unloading. This allows you to start turning immediately after filling the bucket and combine it with lifting the bucket. Lowering the bucket into the face is combined with a reverse rotation. It is also necessary to take into account the location of the access roads: transport should always be supplied from the control panel so that the driver can see its position during unloading. If the soil is loose, then initially scooping should be done only half the width of the bucket so that the soil does not crumble onto the access roads. After three or four such scoops, you can move on to normal work.
First, the lower part of the face is developed using full force of pressure. In this case, the rock sheds from the upper part of the face and the filling of the bucket improves. If the face height is low, the bucket must be filled in two steps. If the face height is less than three times the height of the bucket, you can rearrange the attachment rods of the bucket and handle to increase the cutting angle.
At the beginning of digging, the angle between the handle and the vertical when throwing the bucket is set to at least 10°, since at a lower angle, cutting the bucket into the ground will be difficult. The time for filling the bucket should be reduced by cutting the soil with thick chips, and the bucket should be raised only to a height that ensures its filling.
When working in the face, it is necessary to ensure that collapse prisms, the so-called peaks, do not form (Fig. 35). In cases where they do appear, they should be brought down immediately with a bucket or a pointed log inserted into the bucket. It is necessary to strive to work with incomplete reach of the handle. It is especially not recommended to bring the bucket for unloading at the maximum reach of the handle and at the maximum unloading height, since in this case the time for emptying the bucket increases. However, when scooping loose soils, you need to work at the maximum reach of the handle in order to avoid the excavator from collapsing when the upper layers of soil collapse. In heavy soils, medium and small reach of the handle should be used, which allows you to increase the thickness of the chips and fill the bucket with a “hat”. Working at medium reach in light soils allows you to shorten the excavation cycle.
The place where vehicles stop for loading must be marked with poles or a stop bar must be laid for their rear wheels. This will allow you to work at the same reach of the handle and with the smallest angle of rotation.
Correct operation of the control levers is also of great importance. The levers must be turned on a little earlier than required for a particular working movement, since a fraction of a second passes from the movement of the lever to the activation of the mechanism. This allows you to save up to two seconds per cycle and increase excavator productivity by 10-12%. In addition, the operator must strive to combine working movements: turning with lifting or lowering and moving the handle forward or backward. For an experienced driver, all elements of the cycle smoothly transition into one another and merge with each other. There should be no pauses (breaks) between filling the bucket and the beginning of the turn to unload, between the end of unloading and the return turn to the face. The pressure on the ground to plunge the bucket into it should begin a little earlier than the bucket rests on the ground, and the lift should begin simultaneously with the start of the bucket touching the ground.
Indicators of proper operation of the excavator are the capacity of the dragline bucket usually does not exceed 1 m3.
Preparation of the face when working with a dragline is carried out in the same way as when working with a straight shovel. The excavator parking area and the lane along which vehicles will move are cleared and leveled. Pegs and milestones mark the contours of the face, as well as parking areas for excavators and vehicles (dump trucks or trailers).
Rice. 7. Widened dragline face with transverse-end movement of the excavator
Soil development by draglines can be carried out in the following two main ways: a) end faces, with the movement of the excavator within the strip on which the soil is being excavated;
b) side faces, with the excavator moving outside this strip. With end faces, you can work with a small average angle of rotation of the boom and get fairly wide, symmetrical openings with steep side slopes. The width of the side faces is small, it practically does not exceed 0.7 -0.8 R, but in this case the soil can be unloaded at a considerable distance from the excavation. The choice of development method depends on the type and size of the earthen structure (excavation, channel, pit, embankment, etc.)
To develop excavations with a width of up to 1.2-1.3 R with double-sided laying of soil in dumps and excavations with a width of up to 1.7-1.8 R with loading of soil into transport supplied on both sides of the excavation, it is advisable to use an end face with the installation of an excavator along the axis of the penetration. If the blade or transport path is one-sided, the dragline should be installed offset towards the blade or transport path to reduce the angle of rotation.
Recesses with a width of more than 1.2-1.3 R when laying soil in a dump and more than 1.7-1.8 R when loading soil into a vehicle cannot be dug in a straight line in one dragline pass, so advanced excavator workers have proposed new ways of working that allow increase the width of the passage. These methods include working with the excavator moving in a zigzag and with transverse-end movement.
Dragline techniques
To increase the productivity of an excavator equipped with a dragline bucket, the following work techniques should be used.
When installing an excavator in a face, you need to take into account the direction of the wind, especially if the area is open. It is advisable that the wind blows into the rear or side wall of the body, since in this position sand and small particles of soil will not fall into the driver’s face or fill the excavator.
Work with a dragline should begin from the side of the blade and immediately to the full depth of the excavation, and the bucket should be loaded along the shortest possible path, and the bucket should move without jerking or digging. The cutting depth is adjusted by the height of the attachment of the traction chains to the bucket. In heavy soils, the chains are attached to the lower holes of the bucket's traction eye, and in light soils - to the upper ones.
The lifting rope must not sag during scooping so that the bucket can be lifted immediately after filling. It is also not recommended to pull the bucket too close to the excavator, since the resulting roller of soil contaminates the caterpillar track and interferes with the movement of the excavator.
In the intervals between transport approaches for loading, soil should be collected at distant points of the face, increasing the radius of action of the dragline by throwing the bucket (throwing work). Throwing the bucket is achieved by pulling it up and then releasing the traction drum brake. To prevent the bucket from turning over when throwing it, the traction rope should not be released too much from the winch. It should be borne in mind that throwing the bucket increases the radius of the excavator, but at the same time lengthens the cycle time, so it should not be used unless absolutely necessary.
The development of the face should be carried out at the smallest possible angles of rotation, and to shorten the cycle, the operations of lifting the bucket and turning the excavator for unloading must be combined in time. In this case, the bucket should be smoothly, without jerking, separated from the soil and transported to the unloading site with slightly raised teeth, which prevents soil from scattering. When turning, the bucket should not be raised too high.
Unloading the bucket is performed between two operations: turning to unload and turning to the face. Turning the excavator and lowering the bucket into the face also needs to be combined in time as much as possible. When turning into the face, you should simultaneously throw the bucket so that by the end of the turn it is in a position from which you can begin collecting soil. Unloading the bucket into transport should be done from a minimum height, so as not to damage the car body and not touch the sides with the bucket. The turning brake should be applied a little earlier than the bucket reaches the unloading point. In this case, the bucket moves by inertia towards the vehicle and is unloaded by briefly releasing the traction drum brake.
When working in a dump, unloading must be done on the move. If the angle of rotation for unloading is at least 140°, then the turn back to the face must be made in the same direction without reversing the turning mechanism. The excavator makes a 360° turn. Due to the absence of time loss on braking and acceleration of the turntable, time savings in this case amount to 10-12% of the cycle duration.
Excavator operation with backhoe equipment
Backhoe equipment is installed on excavators with a bucket capacity of only up to 0.65 m3, since excavators with a larger bucket capacity are not stable enough during operation. A backhoe is used when developing soil below the excavator parking level (digging pits, trenches, channels, etc.).
The faces for backhoe excavators, as well as for excavators equipped with a dragline bucket, are divided into two main groups - end and side. Most often, end faces are used, since in this method it is possible to tear off a narrow long trench, which in urban and industrial construction is the main purpose of a reverse excavation.
When digging narrow trenches, the excavator is installed along its axis. When working in a dump, the trench width reaches 0.7-0.8; when working in transport with one-sided unloading, it can be increased to 1.2 R, and with two-sided unloading - up to 1.5 R. To further increase the width of the trench, the excavator is moved not along the axis of the trench, but in a zigzag manner: it is placed at one edge of the trench, That's the other one. This organization of work allows the bucket to be unloaded evenly on both sides of the trench and ensures the required dimensions of the slopes.
Side faces are used in cases where, due to working conditions, unloading should be carried out only in one direction. In this case, the excavator is installed parallel to the axis of the trench, and scooping is carried out perpendicular to the axis. The angle of rotation during unloading increases slightly. Unloading must be done in the direction opposite to the movement of the excavator. With side slaughter, the trench profile turns out to be asymmetrical, since there is a shortage of soil at the opposite wall and the near wall is cut. With this method of operation, the excavator should not be installed too close to the edge of the trench to avoid shedding and collapse of the soil.
A backhoe, like a dragline, is widely used in reclamation work for cleaning and deepening old irrigation canals, as well as for digging new ones. Cleaning and deepening of channels should be done downstream to avoid the formation of a dam, since in this case the flow of water will wash the soil and negate the work of the excavator. If there is no water in the canal, then scooping should be done in the direction of the water. When digging new irrigation canals, it is necessary to take into account that during operation they will have to be cleaned frequently, so the soil should be dumped as far as possible from the edge of the canal.
TO category: - Single-bucket excavators
Excavation work performed by single-bucket excavators is divided into two main groups: non-transport and transport. Without transport are called works in which an excavator, developing soil, places it in a dump, cavalier or in an earthen structure. Non-transport work can be simple or complex. In simple transport-free mining, the soil is placed in a cavalier or embankment without subsequent transshipment (re-excavation). In complex non-transport mining, the soil is placed with an excavator into a temporary (primary) dump, and then partial or complete re-excavation is carried out.
Transport refers to work in which soil is loaded with an excavator and dump trucks and transported to a given location. At the same time, various traffic patterns for group transport are possible; for example, when working with a straight shovel, dead-end and through (dead-end - in which dump trucks approach the excavator and return along the same path; through - in which cars drive up to the excavator without maneuvering and leave after loading the soil on the road, which is a continuation of the entrance route).
The choice of work production system depends on the construction features. Thus, in water management, oil and gas and transport construction, non-transport construction prevails.
work, and in industrial and residential construction - transport.
Soil development is carried out by frontal or lateral penetrations. Lateral penetration is called one in which the axis of movement of the excavator coincides with the axis of the earthen structure or is located in its cross-sectional area.
There are two types of side penetrations: closed, in which the axis of movement of the excavator is located on the side of the excavation section (while moving, the excavator develops three slopes of the excavation - two side and end); open, in which the excavator, moving along the strip being developed, develops the side and end slopes.
Direct execution of work shovel. When using a straight shovel, only transport schemes are used, since due to the small linear dimensions of the working equipment, the excavator cannot provide a sufficient volume of the dump for normal operation. A straight shovel is used when constructing cutting and pioneer trenches in quarries, large pits and excavations in road and hydraulic engineering.
The soil is developed above the level of the excavator parking area with frontal excavators (Fig. 2.1, A- a) or side (Fig. 2.1, G] penetrations. If the width of the frontal penetration is small, the excavator is moved along the center of the penetration; if the width is large, zigzag.
When excavating soil with loading into vehicles, it is recommended to take the following dimensions of penetrations depending on the capacity of the bucket:
0.2 0.4. ..0.5 0.65.. .0,8 1...1.25 1,6...2,5
1,9 2,8 3 3,6 4.5
2.1. Mining with an excavator, equipped straight shovel
s - frontal driving with soil loading on both sides of the face; b- the same, with a double-sided log of soil into vehicles moving along the top of the face; “--a wide frontal passage with loading of soil and vehicles moving along the face; G- side penetration with
soil load and vehicles
 |
2.3. Development reverse recesses shovel A- lateral closed penetration with the same steepness of slopes; b-- the same, with different slope steepnesses; V- side open penetration
Soft soils are developed so that each subsequent digging overlaps the previous one; hard soils - in a checkerboard pattern; deep excavations - with ledges, while first developing a pioneer trench with a frontal or extended face, and then with side faces. The bottom of each ledge should slope towards the development to drain storm water.
When constructing deep excavations in hydraulic engineering and road construction, the design depth of the excavations can significantly exceed the technological capabilities of the excavator. In this case, deep excavations are divided into ledges and tiers, the height of which must correspond to the parameters
excavator frames (Fig. 2.2). Upper part excavations are developed with bulldozers, then part of the excavation is developed with scrapers. The remaining part of the excavation is divided into tiers and excavated using excavators equipped with a straight shovel. At the end of the work, the remaining soil and slopes are finished with draglines.
Performing work with a backhoe. When working with a backhoe, transport and non-transport development schemes are used using lateral (Fig. 2.3) and frontal (Fig. 2.4) penetrations, in which the axis of the working excavator is shifted towards the approach of vehicles. Lateral penetration when working with a backhoe can be open or closed.
2.4. Mining with an excavator equipped with a backhoe frontal tunnelingA- loading soil into vehicles; 6 - to the dump
With open excavation, one side of the workplace remains free of soil. With closed and open side penetrations, the parameters of the structure being developed will be different. Thus, with closed excavation, the steepness of both slopes of the excavation can be set to the same, but it can also be different.
Moreover, in the second case, the possible development depth can be increased by 1.6 times. When developing an excavation using open tunneling, the development depth can be increased by another 20%. However, with such a scheme, the possible volume of the dump and the distance
between the dump and the excavation decrease by about 10 times. This predetermines the need for lateral open excavation to use soil loading into vehicles.
When developing wide pits, the soil is developed by frontal penetrations, while the excavator moves in a zigzag or parallel manner. The dimensions of the penetrations depend on the parameters of the backhoe. When loading soil into transport, the width of the penetration is 1.2...1.3, and when dumping into a dump - 0.5...0.8 of the largest digging radius, and the axis of working movement of the excavator is shifted to the side
2.5. Mining with an excavator equipped with a dragline
A-frontal; b - lateral penetration with loading of soil into vehicles
approach of vehicles.
Excavator and vehicles during unloading. The bucket is installed so that the angle between the axis of the excavator and the longitudinal axis of the vehicle is no more than 40°, and the angle of rotation of the excavator is no more than 70°.
Dragline work. The soil is developed below the excavator parking level using frontal and lateral penetrations (Fig. 2.5) into the dump or into vehicles. The angle of inclination of the boom to the horizon is 30...40°. The depth of development depends on the capacity of the bucket and the length of the boom (Table 2.6). When unloading soil into a dump, the angle of rotation is 90...120°, when loading into a trans-
2.6. Depth of soil development by dragline depending on bucket capacity and lengths: booms, m
| Bucket capacity, m3 | Boom length, and | Prokhodka | ||||
| lateral | frontal | |||||
| 0,4 | 10,5 | 5,3 . | 3,8 | 7.8. | .6,1 | |
| 0,75 | 9,4.. | 7.4 | 10. | .9.2 | ||
| 0.8 | 4,4.. | 3.8 | 7.3. | .5.6 | ||
| 0.8 | 6,6.. | 5,9 | 10. | .7,8 | ||
| 1,0 | 12,5 | 5,5,. | 4,4 | 7,8, | .5.7 | |
| 1,5 | 6.5.. | 5,1 | 9,5. | .7,5 | ||
| 1,5 | 14... | 12,5 | 20,5. | . 16,6 | ||
port located at the same level with an excavator - 180°. Depending on the operating conditions, the transport moves
Mechanical method soil development is based on the use of machines and mechanisms for developing, moving, laying, leveling and compacting soil.
Excavation work generally consists of three processes: excavation development, soil transportation, embankment filling - with the leading process being the development of soil. Development of excavations is carried out in three main ways: cutting, jet erosion and explosive method.
With the mechanical method of development, the cutting force (chipping) of the working body of various machines acts on the soil. As a result, certain portions of soil are separated from the massif and can be moved and placed in an embankment.
During development cutting method is used earth-moving, earth-moving and transport and earth-moving and leveling machines.
Earthmoving machines: excavators, ditch diggers - intended only for soil development.
Earthmoving machines: scrapers and bulldozers - designed to develop soil in an excavation, transport it and dump it into embankments. These machines provide complete mechanization of the entire complex excavation process.
Earthmoving and leveling machines: trailed and self-propelled graders and bulldozers - designed for developing, moving and leveling soil.
To develop soil by eroding a stream of water and moving liquefied soil through pipes, they are used hydraulic monitors, dredging units.
An effective form of mechanized method of excavation work is complex mechanization. The basic principle of integrated mechanization is that all machines involved in performing processes and operations must correspond to each other in their technical, economic and technological parameters.
In this case, the concept of a complex (system) of machines is introduced, and the entire production process is called a complex-mechanized technological process for the production of earthworks.
Depending on the technological processes performed, excavation machines can be divided into the following groups: excavators; earth moving machines; loaders; soil compaction machines; machines and equipment for developing frozen soils; machines and equipment for preparatory work; machines and equipment for drilling wells; machines for hydromechanical soil development; machines for transporting soil.
The main share of earthworks (about 45%) is carried out by single-bucket excavators (EB). The main parameter of the EO is the bucket capacity, m3. To develop EO soil in industrial and civil construction, excavators with a bucket with a capacity of 0.15 - 2 m 3 are used, less often up to 4 m 3. In various industries (coal, mining), single-bucket excavators with a bucket capacity of up to 100 m 3 are used.
Construction excavators are produced on caterpillar and pneumatic wheels. The most common types of work equipment are straight, backhoe, dragline and grab(Fig. 3.1).
The process of developing soil with an excavator with any type of working equipment consists of alternating in a certain sequence of operations in one cycle: cutting the soil and filling the bucket, lifting the bucket with soil, rotating the excavator around its axis to the unloading site, unloading the soil from the bucket, turning the excavator back, lowering the bucket and returning it to its original position.
The maximum dimensions of excavations that can be made by an EO from one parking lot depend on its operating parameters.
Main operating parameters single-bucket excavators when developing excavations are:
maximum possible digging height + N(for an excavator, a straight shovel). The “+” sign indicates that the excavator is digging above its position;
digging depth (cutting) – N(for other types of excavators). The “–” sign indicates that the excavator is digging below its parking lot;
the largest and smallest digging radii at the excavator parking level Rmax And Rmin respectively;
unloading radius Rb;
unloading height Hb.
Rice. 3.1. Operating patterns of hydraulic excavators and face profiles:
A) with a straight shovel; b) with a backhoe; V) with grab equipment;
G) with dragline equipment
EO soil development is carried out positionally. The area in which the excavator operates at a given position is called slaughter It includes the site on which the excavator is located, part of the soil mass being mined from one parking lot, and the site on which transport is installed for loading or a soil dump is located. Upon completion of excavation of the soil in a given face, the excavator moves to a new position.
The excavator and vehicles must be located in the face in such a way that the average angle of rotation of the excavator from the place where the bucket is filled to the place where it is unloaded is minimal, since up to 70% of the working cycle time of the excavator can be spent on the boom rotation time.
Most single-bucket construction excavators are universal machines that can be equipped with various types replaceable working equipment. IN recent years Due to the widespread use of hydraulic drives, the versatility of EO has increased even more. A modern hydraulic excavator can be equipped with more than ten types of working equipment, which significantly expand its technological capabilities.
The use of replaceable working equipment makes it possible to mechanize processes such as: cleaning the bottom of excavations; crushing and removal of oversized debris and boulders; finishing the surface of slopes of earthen structures, the bottom of excavations; layer-by-layer compaction of soil in cramped conditions, when installing backfills; loosening frozen and difficult-to-develop soil.
It is assumed that in further development single-bucket excavators will be associated with the improvement of their technological characteristics, the development of working parts that allow them to flexibly respond to changing work conditions. This will make it possible to fully exploit the potential capabilities of hydraulic machines, which are an example of modern manipulators.
Depending on conditions construction site choosing an excavator begins with determining the most appropriate bucket capacity And excavator type, as well as the required parameters - boom length, cutting radius, unloading, etc. The choice of replaceable excavator equipment depends on the level groundwater and the nature of the excavation being developed (trench, narrow or wide pit). In Fig. 3.2 presents generalized diagrams of penetrations during the operation of various types of excavators.
Basics work equipment EO is used depending on the nature of the work performed.
Excavator with straight shovel– for the development of soils located above the excavator parking area, excavation of soils from pits and reserves with their loading into vehicles.
A straight shovel is an open-top bucket with a cutting leading edge. The bucket is pivotally connected to the handle, which, in turn, is pivotally connected to the boom of the machine and moves forward using a pressure mechanism. The design of the excavator allows it to dig below the level of its parking no more than 10...20 cm; standard productivity can be achieved with a face height of at least 1.5 m. The bucket is emptied by opening its bottom. This design of a straight shovel provides it with the greatest productivity due to filling the bucket with a “hat”.
Rice. 3.2. Drilling patterns for soil development using single-bucket excavators:
A) frontal penetration of a straight shovel with a one-sided arrangement of transport;
b) the same, with bilateral; V) frontal extended penetration with a zigzag movement of a straight shovel; d), and) end penetrations of a backhoe or dragline;
h) widened end penetration during zigzag movement of a backhoe or dragline; And) lateral penetration of a backhoe or dragline;
To) cross-shuttle driving of a dragline; R– cutting radius;
R in– unloading radius; l p– length of movement; IN– pit width
It is not advisable to use an excavator if the groundwater level is higher than the base of the excavation, since the movement of the excavator and vehicles on wet soil is difficult.
The excavation process is carried out using frontal and side faces (Fig. 3.3).
Frontal face used when an excavator develops soil in front of itself and loads it onto vehicles that are fed to the excavator along the bottom of the face or from the side along the natural surface of the earth. In the first case, cars approach in reverse alternately from one side or the other, the size of which at the bottom should not be less than 7 m. Under such operating conditions, the rotation angle of the excavator reaches 140...180°, which significantly reduces its productivity. For these reasons, frontal mining is used extremely rarely, mainly when constructing an entrance ramp into a pit or when developing the first (pioneer) tunneling.
IN technical specifications Usually the maximum values of indicators are given, for example, cutting radius, etc. But working at the maximum values of indicators will lead to rapid wear of the excavator, so it is necessary to assign optimal operating parameters - usually 0.9 Pmax(for example, optimal cutting radius R o = 0,9 Rmax).
Depending on the width of the penetration, frontal faces are divided into narrow(the penetration width is less than 1.5 times the optimal cutting radius R o), normal(width – (1.5…1.9) R o) And widened(width – (2…2.5) R o).
With narrow faces, dump trucks are loaded from one side behind the excavator, and with normal faces, they are fed alternately from both sides of the excavator, which eliminates downtime for the excavator when changing vehicles. With these faces, the excavator moves linearly along the axis of the face.
In some cases, soil development is carried out using a widened face with the excavator moving in a zigzag. In widened faces, the idle penetrations of the excavator are reduced and the conditions for maneuvering and setting up dump trucks for loading are simplified.
Width of frontal penetrations:
for frontal straight
for zigzag
Where R o– optimal cutting radius of the excavator; L p– the length of the working movement of the excavator (the difference between the maximum and minimum cutting radius); R c– cutting radius on a level parking lot.
Rice. 3.3. Drilling diagrams for an excavator with straight shovel working equipment:
A) frontal (end) penetration; b) the same with a two-way arrangement of transport;
V) widened frontal penetration with a zigzag movement of the excavator; G) side penetration; d) development of a pit in tiers; I, II, III, IV – development tiers;
1 – excavator; 2 – dump truck; 3 – direction of traffic
Soil development is more efficient side face, when the bucket is filled with soil mainly on one side of the excavator’s movement and partially in front of itself. According to this scheme, vehicles are supplied for loading from the side of the excavation, which achieves a significant reduction in the angle of rotation of the excavator boom (within 70...90°) when loading soil into vehicles. In side faces, transport routes run parallel to the axis of movement of the excavator and, as a rule, at the level of its parking.
Side penetration width
Recesses whose depth exceeds maximum height the face for this type of excavator is developed in several tiers.
Backhoe Excavator – for the development of soils located below the excavator parking level, mainly when digging trenches, small pits and reserves with loading the soil into vehicles and placing it in a dump. The time spent on one cycle of an excavator with a backhoe is 10...15% more than that of a straight shovel. Tiered excavation is not practiced with this type of equipment.
Backhoe- This is a bucket open at the bottom with a cutting leading edge, pivotally connected to the handle, which, in turn, is pivotally connected to the boom. As you pull it back, the bucket fills with soil. Then, with the handle in a vertical position, the bucket is transferred to the unloading site and unloaded by lifting and simultaneously tipping.
Soil development with a backhoe excavator is carried out using side and frontal faces with loading of soil into transport or into a dump (Fig. 3.4). When side facing, the excavator develops excavations from the side, the width of the excavation is limited by the cutting radius (optimally 0.8 R res), soil development is carried out across the caterpillar track, that is, in the least stable position of the excavator. At frontal At the face, soil is scooped by gradually moving the excavator in reverse; unloading is carried out into vehicles that are fed to the excavator along the bottom of the face or from the side along the natural surface of the earth. The width of the face is limited only by the requirement of normal performance of the mechanism and is 1.5...1.6 R res. During frontal mining, the excavator lowers the boom with the handle to the lowest position between the tracks, so the depth of development of narrow trenches is greater than that of wide ones.
The minimum depth of the face is determined from the condition of filling the bucket with a “cap” (for non-cohesive soils - 1...1.7 m, and for cohesive soils - 1.5...2.3 m). The width of the penetration depends on the largest radius: it is taken in size IN = (1,2…1,5)R o when loading into transport and IN = (0,5…0,8)R o when placing in a dump.
Excavation of a pit with a width of 12...14 m is usually carried out frontal penetration when moving the excavator in a zigzag, and with a larger width - cross-end.
In accordance with current regulatory documents The main working equipment for excavators is currently a backhoe. The excavator can be equipped with the following equipment: a straight shovel, a rigid grab, a hydraulic hammer, a ripper tooth, as well as replaceable buckets of various capacities and purposes.
Rice. 3.4. Drilling diagrams for an excavator with backhoe working equipment:
A) frontal penetration when loading soil into vehicles supplied along the bottom of the face;
b) the same, supplied at the excavator parking level and in a temporary dump;
V) side penetration; 1 – excavator; 2 – dump truck;
3 – direction of transport; 4 – blade
In some cases, excavators (especially with older brands of excavators, including those with cable steering) excavate pits and trenches to a depth slightly less than the design one, leaving a so-called shortfall of a layer of 5...10 cm in order to avoid damage to the base and prevent oversupply of soil. To increase the efficiency of excavators in such cases, you can use a scraper blade mounted on the excavator bucket. This device allows you to mechanize the operation of cleaning the bottom of pits and trenches and carry them out with an accuracy of ±2 cm, which eliminates the need for manual modifications.
Dragline excavator – for developing soils located below the excavator parking level, for digging deep pits, wide trenches, erecting embankments, excavating soil from under water, etc. They are also used for finishing earthworks when leveling areas and cleaning slopes.
The advantages of a dragline are its large range of action
(up to 10 m) and digging depth (up to 12 m). It is especially effective to use a dragline to develop soft and dense soils, including waterlogged ones.
In domestic practice, excavators equipped with a dragline are widely used (about 45%).
The excavator bucket is hung on ropes on an extended crane-type boom. Throwing the bucket into the excavation at a distance slightly greater than the length of the boom, the bucket is filled with soil by pulling it along the surface of the earth towards the boom. Then the bucket is raised to a horizontal position and the machine is turned to move it to the unloading location. The bucket is emptied when the tension in the traction rope is released.
Soil development using a dragline is carried out lateral and frontal penetrations similar to a backhoe excavator. The dragline usually moves between successive stops by 1/5 of the boom length. Depending on the width of the excavation, the method of unloading the soil (into a dump or into vehicles) and the characteristics of the earthen structure, in practice various schemes of frontal and lateral methods of soil development are used.
Since the dragline bucket is suspended flexibly, shuttle operating methods are very effective - cross-shuttle And longitudinal shuttle(Fig. 3.5).
The cross-shuttle scheme makes it possible to pick up soil alternately from each side of the dump truck, supplied for loading along the bottom of the excavation, without stopping the rotation of the boom at the moment of unloading the soil. With a longitudinal shuttle pattern, soil is collected in front of the rear wall of the body and, by lifting the bucket, it is unloaded above the body. In the excavator operating cycle, turns take up most of the time; in this regard, shuttle schemes with a minimum turning angle for loading and unloading are optimal. By reducing the lifting height of the bucket and reducing the rotation angle of the excavator (with a longitudinal-shuttle scheme about 0°, and with a transverse-shuttle scheme 9...20°), the productivity of the excavator increases by 1.5...2 times. Construction dragline excavators are used with a bucket with a capacity of 0.25...2.5 m 3.
Grab – for digging wells, narrow deep pits, trenches and similar work, especially in conditions of developing soils below the groundwater level, extracting sand and gravel from under water.
It is a bucket with two or more blades and a cable or, more recently, rack drive that forces the blades to close. The grab is hung on the boom and develops recesses with vertical walls. When the boom is rotated, the bucket moves to the unloading point and is emptied when the blades are forced to open. Immersion into the ground is carried out only due to its own mass and the forced lowering of the stand, so it is possible to develop soils of low and high density, including those under water. Construction grab excavators are used with a bucket with a capacity of 0.35...2.5 m 3.