The excavation procedure of ventilation shaft is generally as follows: construction of anti-well drilling rig operation platform → construction of anti-well drilling rig foundation and circulating water tank → installation of clean water cylinder with small submersible pump as cooling circulating water for main engine → installation of anti-well drilling rig and commissioning → guide hole construction → reaming construction → removal of drilling rig → ventilation well protection construction.

1. Construction preparation

(1) Operation platform: the working platform of anti-well drilling rig is located on the mixing system platform on the left bank, and the site is relatively open, which can meet the needs of drilling rig foundation, mud circulation pool construction and anti-well drilling rig operation.

(2) Road: The maximum weight of LM200 anti-well drilling rig is 8t. The road formed by the preliminary engineering construction can basically meet the transportation requirements of anti-well drilling rig components, and there is no need to set up another transportation road.

(3) Loading and unloading: 25t truck crane shall be used to hoist the anti-well drilling rig and auxiliary equipment outside the tunnel; when replacing the reaming drill bit in the tunnel, it shall be installed manually with ZL50 loader.

(4) Anti-well drilling rig foundation: take the center of the ventilation shaft as the center, chisel the poured concrete of the foundation, and after washing, pour C20 concrete, and control the flatness of the concrete surface within ± 1.5cm. In order to ensure the stability of the foundation of the main engine of the anti-well drilling rig, 12 Ф 25 dowels @ 120 × 120cm, L = 70cm and 30cm exposed are set on the foundation surface. The foundation size of the main engine of the anti-well drilling rig is 4.0 × 3.0m (length × width) and 30~115cm high. The foundation platform is reserved for 1.2 × 1.2m ventilation shaft reaming outlet. The anchor bolt hole is reserved on the foundation of the main engine, and the size of the reserved groove is 1.6 × 0.55m (length×width)

The foundation construction procedure of anti-well drilling rig is as follows: construction setting-out (determination of excavation scope) → steel dash construction → foundation surface construction → pouring foundation concrete → installation of drilling rig.

(5) Mud tank: set up a 8m3 tank at an appropriate position around the drilling rig foundation, with a length × width × depth of 6.5 × 3.0 × 0.5m. The pool is built with hollow bricks, the surface is plastered with mortar, and a partition wall is set in the middle to separate the pool into a clean water tank and a sedimentation tank. The main engine foundation and the sedimentation tank are connected by a ditch with a slope of I = 10 ~ 15%. The backwater and fine sand from the guide hole construction flow back to the sedimentation tank along this ditch. Before working, the specific location of the mud pump shall be determined according to the installation location of the main engine and the specific conditions of the site.

(6) Cooling water tank A cleaned oil cylinder or water tank is placed on site, and a small submersible pump is placed for circulating cooling oil pump.

(7) Installation, commissioning and commissioning of drilling rig

After the rig is transported to the site, the rig will be installed and debugged. The main tasks include:

1) Turn on the power supply of all motors, briefly energize and observe the steering of the motors.

2) Connect the oil inlet and return pipelines from the drilling rig pump truck to the operating truck and drilling rig.

3) Install manipulator and turntable crane.

4) Rig leveling and alignment.

5) Install the lower support and front and rear diagonal tie rods.

6) Pour the bolt holes of the ground feet (Phase II concrete).

7) Connect the cooling water system.

8) Commissioning the mud pump to form a water (mud) circulation system.

2. Guide hole drilling

The pilot hole drilling is the key to the construction of anti-well drilling. It is related to the success and quality of drilling and must be taken seriously.

(1) Drilling parameters The selection of drilling parameters is mainly based on formation conditions, drilling sites and other factors. Generally, the construction is carried out according to the parameters shown in the following table, but it shall be adjusted according to different conditions during construction.

(2) When the main engine, oil pump and operating system are ready, check whether the mud pump pipeline is connected with the main engine, whether the circulating cooling system of the main oil pump is debugged, and the drilling center and drilling angle are verified to be accurate, then the hole can be opened. When drilling the hole, the hole centralizer and the hole drill pipe must be used to cooperate with the slow hole opening, and the mud pump must be started to supply water (slurry supply). The depth of the hole is 3m. After the hole is opened, the hole drill pipe shall be lifted out, wiped with oil after cleaning and preserved.

(3) Guide hole drilling Guide hole drilling must be fully coordinated, must do the following:

1) Under normal circumstances, the drilling speed of the pilot hole should be higher than that of the drilling speed of the opening hole, so the speed of the power head should be adjusted, and the second or third gear can be used. Under normal circumstances, low WOB should be used for soft formations and transition formations, and high WOB should be used for hard rocks and stable formations.

2) It is about 3 m away from the horizontal passage under the drilling penetration, and the WOB shall be gradually reduced.

3) The rock ballast drilled in and out of the guide hole must be cleaned in time to prevent the accumulation of rock ballast. The rock ballast cleaning is completed by backhoe or manual cooperation with trolley.

4) After a drill pipe is completed, the pump must be stopped to pick up and unload the drill pipe after all the cuttings in the hole are discharged.

5) No personnel shall operate within 10m from the center of the well before the pilot hole is drilled through, and the tip of the ballast bucket of the loader shall not be less than 5m from the reaming center.

6) After the pilot hole is drilled through, stop the mud (water) circulation, but the drilling rig cannot stop, start to add clean water into the hole, and stop drilling until the drilling rig rotates smoothly and the torque changes little.

7) During the whole pilot hole drilling process, power failure and water cut-off shall not occur in the middle, otherwise it will lead to serious accidents such as sticking.

8) Treatment of hole collapse of guide hole of anti-well drilling rig: during the construction of guide hole, when hole collapse occurs in large fault or fracture zone, cement slurry shall be consolidated on the hole collapse section before drilling down.

3. Reaming and drilling

(1) Remove the pilot bit and connect the reaming bit. After the pilot hole is drilled through, transport the reaming bit and the pilot bit removal tool to the lower opening. Contact up and down through interphone or telephone, and cooperate up and down to remove the pilot drill bit and connect the reaming drill bit.

(2) Reaming drill into the reaming hole, when the reaming bit is connected, slowly lift the drilling tool. Until the hob starts to contact the rock, then stop lifting, rotate at the lowest speed (5~9rpm), and feed slowly to ensure that the drill hob is not damaged by excessive impact, stop feeding, wait for the knife teeth to crush the protruding rock, and then continue to feed. When reaming is started, someone should observe below and inform the operator of the situation in time. Only when the drill bit contacts the rock evenly can the reaming and drilling be performed normally. In order to ensure the service life of the drilling rig and hob, the system pressure is generally limited to 18Mpa. In the process of reaming, when the rock hardness is large, the drilling pressure can be appropriately increased, on the contrary, the drilling pressure can be reduced. During reaming and drilling, the broken rock debris shall be cleaned in time to prevent the lower opening from being blocked. The reaming process is also the process of removing the drill pipe. The removed drill pipe shall be cleaned as necessary and oiled with a protective cap.

4. Breakage

During the reaming construction, the ballast slipped along the rock wall of the ventilation shaft into the 1# construction adit, and the ballast was transported by ZL50 rollover loader and 25t dump truck. The ballast was discharged once every 5m during the reaming construction, with a square volume of about 6m. The outlet of ventilation shaft is located at the intersection of 1# construction adit and 1# water diversion channel. Excavation and support construction is being carried out on the downstream side of the upper section of 1# water diversion channel. The adjacent working face is close, so construction interference will inevitably occur. In the construction process, should strengthen the construction coordination, overall arrangement, reasonable organization of production operations, to ensure that the face construction in an orderly manner.

5. Finish the hole

When the drill bit is 2.5m away from the foundation, it is necessary to reduce the weight on bit and drill slowly, and carefully observe whether there is any abnormal phenomenon around the foundation, and take timely measures to deal with it. Slowly ream the hole until the drill is above the ground.

6. Demolition construction

(1) First, fix the reaming drill bit, remove the front and rear inclined pull rods and various oil pipes of the drilling rig, remove the main machine from the drilling frame, and remove the main machine of the drilling frame and some auxiliary equipment. Hang the reaming bit firmly and lift it out of the hole. Then lift the operating truck up, remove the pump truck and oil tank cooler, and complete the disassembly.

(2) Remove the foundation platform of the drilling rig and the water pool. After the drilling rig and auxiliary equipment are evacuated, the foundation concrete platform and circulating water pool shall be removed manually.