Productivity of bulldozers. Calculating the productivity of the bulldozer

In the development of excavations, excavations and embankments it is advisable to use a bulldozer equipment set if the average range of longitudinal or transverse carriage does not exceed 100 meters. To choose the most optimal model of special equipment, it is necessary to compare the performance of bulldozers with different traction class and different types of working equipment.

The most promising are the machines on the caterpillar engine. Technique on a pneumatic wheel drive is in demand less. When calculating the productivity of an earth-moving machine, it is necessary to take into account the conditions of the terrain, the nature of the work and other factors.

Basic information about bulldozers

The bulldozer is a digger-transport machine for layer-by-layer development and transportation of soil, developed on the basis of a caterpillar or pneumatic-wheeled tractor with interchangeable attachments - a blade (flat shield with lateral openings), a frame and a control mechanism. A technique is used with a non-turning and swivel blade. In the first case, the working equipment is located perpendicular to the longitudinal axis, which allows you to move the soil masses just ahead of the machine. The performance of bulldozers with a rotary blade is much higher, since such specimens are able to move the soil to the side at an angle of 60 degrees, which allows for rough planning work.

The control mechanism of the blade can be cable-block and hydraulic. The second type of control is more productive, since it allows forcing the blade to be forced into the ground.

Traction class of cars

With the help of bulldozers, up to 40% of all excavation work is carried out at the construction site. They are most effective at an average range of longitudinal and transverse cars from 100 to 150 meters. When equipping machines with special scoops, the effective range of the sandy soil is increased up to 200 meters. The main parameter affecting productivity is the traction class - the force with which the bulldozer can push the soil forward. The technical characteristics of machines affect the volume of the moving earth massif, the speed of work. According to this parameter, all bulldozers are divided into three groups:

1. Light, traction force which does not exceed 60 kN. They are used during preparatory, agricultural and auxiliary works.
2. Medium, with a pulling force of 100-150 kN. Used for the development of 1-3 groups of soil with preliminary loosening.
3. Heavy, pulling force of which exceeds 250 kN. They are used in the development of dense and hard rocks.

Bulldozers are used in conjunction with other digging machines. They can be used as pushers for self-propelled and trailed scrapers. Typically, a bulldozer equipment set includes a ramming machine and a ripper.

Factors affecting performance

Expecting the productivity of bulldozers, it is necessary to take into account the physical and mechanical characteristics of the developed land massif, as well as local conditions. The basic physicomechanical characteristics of the soil include:

• Granulometric composition - the ratio of the particle size of the soil by mass;
• Density - the mass of the soil in a unit of its volume;
• Porosity - the number of voids between grains, expressed as a percentage of the mass;
• The plasticity number is the humidity range in which the soil has plastic properties and does not change to a fluid state;
• Swelling - the ability of the land mass to increase in volume when waterlogged;
• Angle of internal friction - resistance of soil particles to the cut.

Local conditions affecting the productivity of bulldozers include the nature of the relief and the technological features of the construction site. On a flat and straight section with a minimum range of transverse load, the speed of work is much higher than in a hilly terrain.

Calculating the productivity of bulldozers

The performance of the bulldozer depends on the type of work performed. This can be earth-moving or planning work. In the first case, the productivity is expressed in m ³ / h, in the second - m ² / h. More details on earth-moving works.

The operational capacity is determined by the volume of the land mass that the special machinery can develop and move per unit of time, that is, in one hour. Calculation of the bulldozer's productivity is carried out according to the formula To calculate the performance, as close as possible to the real, introduce correction factors:

• K _y is the effect of the slope of the ground. During operation on gradients from 5-15% the value increases from 1.35 to 2.25; When developing the ground on the rise, the coefficient decreases from 0.67 to 0.4;
• K _в - value that takes into account the time of use of the machine (k _в = 0,8-0,9);
• K _н - coefficient of filling the geometric volume of the prism of drawing (k _н = 0,85-1,05).

To calculate the productivity, it is also necessary to know the volume of the prism of drawing (V _gr ) and the length of the working cycle of the machine (T _c ).

Calculation of the prism of the drawing

A characteristic feature of the machine is the fact that the bucket of the bulldozer moves the soil in the so-called drawing form. The volume of the prism is calculated from the formula Here B and H are the length and height of the blade, respectively, k _{n the} coefficient of land loss during its movement, is assumed to be 0.85-1.05, k _p is the degree of loosening of the soil.

Duration of the cycle

To calculate the duration of the working cycle, that is, the time that the tractor bulldozer will spend on the development of one layer of soil, it is necessary to understand that the entire length of the longitudinal or transverse carriage is divided into several segments. The duration itself is calculated by the formula Here l _p , l _n and l _o = l _p + l _n - the lengths of the cutting areas, the movement of the soil massif and the reverse travel of the special equipment, and v _p , v _n and v _o - the maximum possible speeds in these sections. The coefficient t _n takes into account the time that the driver spends on shifting gears during operation. Usually it is 15-20 seconds.

Bulldozer performance with a wedge work pattern

The application of the wedge scheme of the ground set is possible only with those machines that are equipped with a hydraulic blade control mechanism. This, for example, is the bulldozer "Shantui SD32". A distinctive feature of this principle of soil development is the fact that the cutting force gradually decreases as the prism of the drawing increases. At the beginning of the work, all the forces of the machine are aimed at dumping the dump into the ground to a maximum depth h _max and cutting the land mass. As the motion of the soil accumulates in front of the bulldozer, because of which increases the resistance to movement. For further work, the operator must increase the applied tractive effort or reduce the depth of cut.

Thickness of earth shavings

Most often resort to the second option, but in this case a part of the earth is "lost" in the lateral ridges (the worse is the "Shantui" bulldozer). To compensate for these losses, the machine along the entire path of movement must cut off the "shavings", which is calculated by formula Here k _n - Correction taking into account ground losses during transportation, k _pr coefficient of the prism of drawing, which is taken from the performance characteristics of the machine, L _n is the length of the section on which the ground is cut. It is defined as the ratio of the volume of the prism drawn to the area of the site being developed.

Impact of blade type on performance

Depending on the characteristics of the ground, as well as the tasks assigned to the bulldozer, it is advisable to use certain types of dumps. This will shorten the period of production, as well as increase the efficiency of special equipment.

Any machine is equipped with a replacement blade, including the Komatsu bulldozer of Japanese manufacture. Among the main types of working equipment is:

• Recultivation subspecies, which is used to remove the upper fertile layer of the earth, chernozem;
• A variety for the movement of coal and chips - is used in the development of minerals, has a hemispherical shape and a hydroisperoscope;
• "Peat" variety has a reduced height, but an increased length and is used to enrich the agricultural fields;
• Dumps for the preparation of the site - brush cutters and trimmers, which are equipped with teeth, are produced in V-shaped and designed to clear the terrain from trees and shrubs.

The most progressive (in terms of the possibility of installing various working equipment) is the Japanese Komatsu bulldozer. All models of special equipment can be equipped with any of the presented dumps, which gives them high functionality and makes universal machines for the construction site.

Calculation of the performance of the bulldozer must be carried out to reduce the cost of excavation. On the basis of the data obtained, it is possible to select the most suitable for the work of special equipment, shorten the period of production and save a lot of money.