A complete analysis of the tunneling process of the coal mine excavation face

In the complex system of coal mining, tunneling work is a crucial first link. It is like a key that opens up channels for subsequent key steps such as coal mining and transportation. The safety and efficiency of tunneling work are directly related to whether coal mine production can be smoothly promoted and the realization of overall economic benefits. Next, we will take the widely used cantilever tunneling machine as an example to explain the complete process flow of the tunneling face in depth and comprehensively.

I. Careful preparation before operation

(I) Detailed inspection of equipment

The cutting mechanism of the cantilever tunneling machine is the core component and requires extra care during inspection. Focus on the cutting head teeth and confirm whether there are signs of wear one by one. Make sure that the teeth are not loose or broken and are in good condition. At the same time, focus on checking whether the telescopic and swinging movements of the cantilever are smooth and smooth, and whether there are any jams or abnormal sounds, which directly affects the accuracy and efficiency of the cutting operation.

The loading mechanism should not be ignored. The tension of the scraper conveyor chain should be strictly checked. If the chain is too loose or too tight, it may cause chain skipping, chain jamming and other faults, which will affect the efficiency of coal and rock transportation. It is also necessary to check whether the scraper is intact. If it is damaged, it should be replaced in time. For the belt conveyor, it is necessary to carefully check the wear degree of the belt and check whether there is any deviation. Once a problem is found, it must be adjusted in time to ensure the stability and safety of the transportation process.

The walking mechanism is related to the mobility of the tunnel boring machine. The tension of the crawler should be fully checked to ensure that the crawler is stable and reliable during operation. At the same time, pay close attention to the wear condition of the drive wheel and the guide wheel. If the wear is serious, it needs to be repaired or replaced in time to ensure the normal walking of the tunnel boring machine and enable it to reach the working position flexibly.

(II) System performance test

As the key to the power transmission of the tunnel boring machine, the hydraulic system should be fully inspected for its oil pump, valve group and oil pipe. The oil pump needs to operate normally, with stable output pressure, to provide sufficient power for each actuator; the valve group should be flexible and leak-free to ensure accurate flow and pressure control of hydraulic oil; the oil pipe connection should be firm, without damage, aging, etc., to ensure the stability of the pressure of the entire hydraulic system and no leakage, so as to ensure the smooth operation of each action of the tunnel boring machine.

The electrical system is the "nervous system" of the tunnel boring machine and should not be ignored. Check whether each electrical component is intact, whether the line connection is firm and reliable, and whether the insulation performance is good, which is related to the safety of equipment operation. The display of various instruments should be accurate so that the operator can grasp the operating status of the equipment in real time, ensure that the electrical system can operate safely and stably, and provide reliable power support for tunneling operations.

(III) Environmental safety assessment

Safety is the primary principle of coal mine production. It is crucial to use professional testing instruments to accurately detect the concentration of harmful gases such as gas and carbon monoxide at the tunneling working face. Ensure that the concentration of these harmful gases is always within the safe range. If the concentration of harmful gases exceeds the standard, effective ventilation measures must be taken immediately until the standard is met before continuing the operation to prevent safety accidents such as gas explosions and poisoning.

Carefully check the rock stability of the roof and the two sides. For the existing floating stones and dangerous rocks, they must be cleaned and handled in time to prevent them from falling and injuring people during the excavation process. At the same time, comprehensively clean up the debris and accumulated water on the working surface to create a safe and smooth environment for the movement of equipment and personnel, and avoid accidents caused by environmental factors.

2. Orderly implementation of excavation operations

(I) Accurate positioning

With the coordinated assistance of the traction equipment, the tunnel boring machine slowly moves to the starting position of excavation. In this process, with the help of the laser pointer equipped on the machine body, and closely combined with the center line and waist line of the tunnel, the position and angle of the tunnel boring machine are accurately adjusted. The laser pointer is like a "navigator" for the tunnel boring machine, ensuring that the cutting head can accurately align with the excavation direction, laying a solid foundation for subsequent cutting operations, and ensuring that the tunnel is excavated in the designed direction to avoid deviations.

(II) Layered and segmented cutting

Start the cutting head and the cutting operation officially begins. First, perform horizontal cutting from one side of the bottom of the working face. The cutting depth is strictly controlled between 0.3 and 0.5 meters. This is a reasonable depth determined based on rock characteristics, equipment performance and other factors. When the cutting head reaches the other side of the tunnel, lift the cutting head to a certain height and perform horizontal cutting again. Repeat this cycle to gradually achieve layered cutting. When encountering hard rock, the rock hardness increases, which has an impact on the equipment and operation safety. At this time, it is necessary to appropriately reduce the cutting speed, increase the number of cuttings, and reduce the cutting depth each time to ensure the safety and efficiency of the cutting operation and avoid excessive wear or damage to the equipment.

III. Close coordination between coal and rock transportation and support

(I) Timely slag removal

The cut coal and rock are transported to the belt conveyor in an orderly manner through the scraper conveyor, and then quickly transported out of the excavation working face by the belt conveyor, and finally transferred to the ground or a designated storage location. The entire transportation process must be kept smooth. Blockage, accumulation and other problems in any link may lead to interruption of the excavation operation. Therefore, it is necessary to regularly check the transportation equipment to ensure its normal operation and the continuity of the excavation operation.

(II) Temporary support

During the excavation process, when the excavation distance reaches 1-1.5 meters, the roof loses its original rock support and is in an unstable state. The excavation must be stopped immediately and temporary support operations must be carried out quickly. The front exploration beam is used in conjunction with metal mesh, backboard and other support materials to temporarily support the roof. The front exploration beam is like a "protective umbrella", which effectively prevents the roof from collapsing, ensures the safety of the workers, and creates safe conditions for subsequent operations.

(III) Permanent support

When the excavation distance reaches 3-5 meters, the permanent support operation is started in a timely manner. First, the anchor rod construction is carried out according to the spacing and angle required by the design. After the drilling is completed, the anchor rod is accurately inserted, and the tray and nut are installed. The appropriate pre-tightening force is applied to make the anchor rod closely combined with the rock mass to form an effective anchoring force to ensure that the anchor rod can effectively play a supporting role.

Then the anchor cable construction is carried out. The length and anchoring force of the anchor cable need to be reasonably determined according to the specific geological conditions and actual needs of the tunnel. The anchor cable is like a large "nail" that penetrates deep into the rock mass to provide stronger support. After the construction of anchor rods and anchor cables is completed, the shotcrete operation is carried out to spray the concrete evenly onto the surface of the tunnel to form a support layer of a certain thickness, further enhancing the stability of the tunnel and resisting the deformation and damage of the rock mass.

IV. Strict implementation of the finishing inspection work

(I) Equipment shutdown and cleaning

After the successful completion of the excavation operation, strictly follow the operating procedures to shut down the cutting head, scraper conveyor, belt conveyor, oil pump and other equipment in turn to avoid equipment failure or safety accidents caused by misoperation. Subsequently, the coal dust and rock slag on the surface of the tunneling machine are thoroughly cleaned to keep it clean and prevent the accumulation of coal dust from affecting the heat dissipation and operation of the equipment. At the same time, the key parts of the equipment are lubricated and maintained to make full preparations for the next operation, extend the service life of the equipment, and reduce the equipment failure rate.

(II) Quality acceptance

The excavation size and support quality of the tunnel are strictly and meticulously inspected and accepted. Accurately measure the width, height, slope and other parameters of the tunnel to ensure that they fully meet the design requirements and that the tunnel can meet the space requirements for subsequent coal mining, transportation and other operations. Check whether the anchoring force and preload force of the anchor rods and anchor cables meet the standards, and whether the thickness and strength of the shotcrete meet the design standards. Any problems found during the inspection must be rectified in a timely manner to create good conditions for the next excavation operation and ensure the safety and efficiency of the entire coal mining process.