The excavator is one of the main construction machinery in earth rock engineering, which is mainly composed of power unit, transmission system, action system, slewing mechanism, operating mechanism, electrical equipment and working device. The working devices are changed into more than ten types according to different operation requirements, so they are widely used in highway, railway, construction, mine, water conservancy, national defense and other projects. According to statistics, more than 60% of the earth rock works in various projects are completed by excavators. At present, backhoe excavator is mainly used in highway engineering. The application of backhoe excavator in highway construction is mainly introduced below.

1、Basic Operation of Backhoe

Backhoe excavator is mainly used to excavate earth and stone in highway construction, and its basic operation modes include ditch end excavation and ditch side excavation.

1.1、 Trench end excavation

During excavation, the backhoe excavator shall gradually reverse along the trench end and excavate backwards. The dump truck stops at the side of the ditch, and the excavator can unload as long as the pen rotates 40 °~45 °. If the width of the trench to be excavated is twice of the excavation radius of the backhoe excavator * (that is, every time the backhoe excavator is parked, it is excavated within the 180 ° rotation range), the dump truck can only be parked at the side of the backhoe excavator, and the excavator boom needs to make a 90 ° rotation before unloading. If the width of the trench excavated is more than twice of the larger excavation radius, excavation shall be carried out by sections, that is, after the backhoe excavator reverses excavation to the end, the adjacent section shall be reversely excavated at the transfer position at the end. The excavation width of each section of this method should not be too large. Based on the principle that the dump truck can run at the ditch side, the time of each working cycle can be reduced and the working efficiency of machinery can be improved.

1.2   Trench side excavation

The backhoe excavator excavates at the side of the ditch, the truck receives materials at the end of the ditch, and the boom of the excavator rotates less than 90 ° for unloading. Each excavation width (trench width) of this method can only be within its excavation radius, and the disadvantage is that the slope of trench excavation is large.

2、 Construction operation of backhoe excavator

Backhoe excavator is often used to excavate ditches and fill embankments in highway engineering construction, and generally needs to cooperate with dump truck. During the subgrade earthwork construction, the appropriate type (bucket type, bucket capacity) of backhoe excavator shall be selected according to the site construction conditions (such as terrain, location of soil fetching and delivering, soil grade, block size of stone), earthwork volume, construction progress and other requirements, and then the construction scheme shall be designed according to the selected backhoe excavator performance (boom and bucket handle length, excavation radius, excavation depth).

2.1   Excavation of cutting

When excavating the cutting, the soil shall be removed in strict accordance with the longitudinal and cross section drawings of the cutting, without exceeding or underexcavation. In order to correctly prepare the construction scheme for cutting excavation, first, the working section diagram of the excavator shall be designed in proportion to the performance of the selected backhoe excavator, and then the working section diagrams of various layout schemes shall be plotted on the cutting section diagram of the same scale, from which the * construction scheme shall be determined. The * construction scheme shall minimize the number of tunneling roads, the transfer times of transportation roads and the remaining soil angle; The * depth of each heading road working section (tunnel face) shall not exceed the allowable depth of this type of soil and this type of excavator; The roadways shall have large gentle slopes to facilitate the transportation of dump trucks and drainage in rainy seasons. The working section of the backhoe excavator shall be marked with the roadways (excavation levels), pile numbers, dump truck positions, and the curve contour of the working section. In addition, there should also be a working section at several mileage stake points of the cutting profile to accurately determine the excavation location, working road and calculate the excavation earthwork.

2.2   Embankment filling

In order to speed up the construction progress and save the construction cost, the excavation of cutting by backhoe excavator is generally carried out together with the filling of embankment, that is, the earth and rock excavated by backhoe excavator is used to fill the embankment (referred to as excavation for filling). If the earthwork excavated from the cutting is not suitable for filling the embankment (such as humus soil and cohesive soil with large water content, etc.) or is insufficient for the earthwork required for embankment filling, the backhoe excavator shall be used to fill the embankment. That is, open up favorable terrain in the selected borrow area, excavate the required amount of soil by backhoe excavator with economic and reasonable construction method, transport the soil by dump truck, and fill the embankment together with other earth rock engineering machinery (bulldozer, grader, compaction machinery, etc.). However, the construction scheme must be designed in advance for the backhoe excavator to cooperate with dump truck and other earth rock engineering machinery.

In order to improve the construction quality and speed up the construction progress, the backhoe excavator, dump truck and other earth rock engineering machinery often organize flow operation during the construction. When designing flow operation procedures, they should be organized reasonably according to the total amount of work, road section length, flow direction and speed, and construction period. Flow process is dominated by backhoe excavator. First, determine the productivity and quantity of backhoe excavator according to the total amount of work and construction period, and then estimate the productivity and quantity of other supporting machinery (dump truck, bulldozer, grader, roller) according to the productivity of backhoe excavator. The productivity of the supporting machinery should be reserved slightly to give full play to the production capacity of the backhoe excavator.