When developing pits, excavations and embankments, it is advisable to use a bulldozer set of equipment if the average distance of the 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 various types of working equipment.
The most promising are crawler vehicles. Pneumatic-wheel equipment is less in demand. When calculating the performance of an earth moving machine, it is necessary to take into account the terrain, the nature of the work and other factors.
Bulldozer Basics
A bulldozer is an earth moving machine for layer-by-layer excavation and transportation of soil, developed on the basis of a caterpillar or pneumatic wheel tractor with interchangeable mounted working equipment - a blade (a flat shield with side flaps), a frame and a control mechanism.
Applied technology with fixed and rotary blade. In the first case, the working equipment is perpendicular to the longitudinal axis, which allows you to move soil masses only in front of the machine. The productivity of bulldozers with a rotary blade is much higher, since such instances are able to move the soil to the side at an angle of 60 degrees, which allows for rough planning work.
The blade control mechanism can be cable-block and hydraulic. The second type of control is more productive, as it allows you to forcibly dig a dump into the ground.
Traction class cars
With the help of bulldozers, up to 40% of all excavation work on the construction site is carried out. They are most effective with an average range of longitudinal and transverse carriage from 100 to 150 meters. When machines are equipped with special dumps of the soviet type, the effective range of carriage of sandy soils increases to 200 meters.
The main parameter affecting productivity is the traction class - the force with which the bulldozer can push the soil forward. Technical characteristics of machines affect the volume of the moved massif of land, the speed of work. According to this parameter, all bulldozers are divided into three groups:
- Lungs, traction of which does not exceed 60 kN. They are used during preparatory, agricultural and auxiliary works.
- Medium, with a pulling force of 100-150 kN. Used to develop 1-3 groups of soil with preliminary loosening.
- Heavy traction which exceeds 250 kN. They are used in the development of dense and hard rocks.
Bulldozers are used in combination with other earthmoving machines. They can be used as pushers for self-propelled and trailed scrapers. Typically, a bulldozer kit includes a rammer and cultivator.
Performance Factors
When calculating the productivity of bulldozers, it is necessary to take into account the physical and mechanical indicators of the developed land mass, as well as local conditions. The main physical and mechanical characteristics of the soil include:
- particle size distribution - the ratio of the size of soil particles by weight;
- density - soil mass per unit volume;
- porosity - the number of voids between grains, expressed as a percentage by weight;
- plasticity number - the moisture range in which the soil has plastic properties and does not go into a fluid state;
- swelling - the ability of the massif to increase in volume during waterlogging;
- angle of internal friction - resistance of soil particles to a slice.
The local conditions that affect the performance of bulldozers include the nature of the terrain and the technological features of the construction site. On a flat and straight section with a minimum range of transverse carriage, the speed of work is much higher than on hilly terrain.
Bulldozer performance calculation
Bulldozer performance depends on the type of work performed. This can be earth moving or planning work. In the first case, productivity is expressed in m 3 / h, in the second - m 2 / h. Let us dwell on earth moving operations.
Operational productivity is determined by the volume of land mass that special equipment is able to develop and move per unit of time, that is, in one hour. The calculation of the productivity of the bulldozer is carried out according to the formula
To calculate the performance that is as close as possible to the real one, correction factors are introduced:
- k y - the influence of the slope of the earthen site. During operation on slopes from 5-15%, the value increases from 1.35 to 2.25; when developing soil on a rise, the coefficient decreases from 0.67 to 0.4;
- k in - value taking into account the time of use of the machine (k in = 0.8-0.9);
- k n - coefficient of filling the geometric volume of the drawing prism (k n = 0.85-1.05).
To calculate the productivity, it is also necessary to know the volume of the drawing prism (V gr ) and the duration of the working cycle of the machine (T c ).
Calculation of the volume of the drawing prism
A characteristic feature of the machine is the fact that the bulldozer bucket moves the soil in the so-called drawing form. In this case, the prism volume is calculated by the formula
Here, B and H are the length and height of the blade, respectively, k
n is the coefficient for accounting for land losses during its movement, is taken equal to 0.85-1.05, k
p is the degree of loosening of the soil.
Cycle duration
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 sections of cutting, displacement of the soil mass and the reverse stroke of special equipment, and v
p , v
n and v
o are the maximum possible speeds in these sections. The coefficient t
n takes into account the time that the driver spends on gear shifting during operation. Usually it is 15-20 seconds.
Bulldozer performance with wedge pattern
The use of a wedge pattern of soil collection is possible only with those machines that are equipped with a hydraulic blade control mechanism. Such, for example, is the Shantui SD32 bulldozer. A distinctive feature of this principle of soil development is the fact that the cutting force gradually decreases as the drawing prism increases.
At the beginning of the work, all the forces of the machine are aimed at immersing the blade into the ground to a maximum depth of h
max and cutting the soil mass. As it moves, soil accumulates in front of the bulldozer, which increases the resistance to movement. For further work, the driver must increase the applied traction force or reduce the cutting depth.
Earthen chip thickness
Most often they resort to the second option, but in this case part of the land is “lost” in the side rollers (which is why the Shantui bulldozer is also bad). To compensate for these losses, the machine along the entire path of movement must cut off the "chips", which is calculated by the formula
Here k
p -
correction taking into account soil loss during transportation, k
pr the coefficient of the prism of the drawing, which is taken from the operational characteristics of the machine, L
p - the length of the section on which the cutting of the soil. It is defined as the ratio of the volume of the drawing prism to the area of the developed section.
Impact type of blade on performance
Depending on the characteristics of the soil, as well as on the tasks assigned to the bulldozer, it is advisable to use certain types of dumps. This will shorten the duration of work, as well as increase the efficiency of special equipment.
Any machines are equipped with a replacement blade, including a Japanese-made Komatsu bulldozer . Among the main types of working equipment it is worth highlighting:
- reclamation subspecies, which is used to remove the upper fertile layer of the earth, chernozem;
- a variety for moving coal and wood chips - used in the development of minerals, has a hemispherical shape and a hydroperiscope;
- "Peat" variety has a reduced height, but increased length and are used to enrich agricultural fields;
- dumps for site preparation - brush cutters and uproots, which are equipped with teeth, are produced in a V-shape and are designed to clear the area from trees and shrubs.
The most progressive (in terms of the ability to install various working equipment) is the Japanese Komatsu bulldozer. All models of special equipment can be equipped with any of the dumps presented, which gives them high functionality and makes them universal machines for a construction site.
The calculation of the productivity of the bulldozer must be carried out to reduce the cost of excavation. Based on the data obtained, it is possible to choose the most suitable special equipment for work, shorten the period of work and save a lot of money.