【Construction case】SJL-120 rotary jet drilling rig was constructed in MJS

Stratum situation

Location (province): Zhejiang Province

Location (city): Hangzhou

Drill model: SJL-120 rotary jet drill

Process type: rotary spray reinforcement

Construction technology: MJS construction method

Stratigraphy: 1-3 meters backfill, 3-25 rice flour sand layer contains a small amount of mud

Construction Angle (°): 90

Pile diameter (mm): 2,400

Hole depth (m): 19

Construction technology

Configuration:

① A hole introduction drill, with 89 drill rod + 250-300 three-wing drill bit;

② A SJL-120 rotary jet drill, equipped with 142 porous drill + 142 porous drill rod + porous shunt + 25 diameter 6-layer high pressure pipe + 19 diameter 4-layer high pressure pipe;

③ One 230 high pressure grouting pump, two 90E high pressure grouting pumps (one pre-cut water and one reverse slurry water);

④ A 10 kg 12 cubic air compressor, pressure to ensure 0.8~1.0Mpa;

⑤ A car crane;

⑥ A return mud pump;

⑦ A fully automatic mixing station;

⑧ A set of cement tanks.

1、According to the requirements to determine the pile position, first with the hole drill, due to the characteristics of silt formation-cohesion is very small, easy to lead to hole collapse, it is recommended to use bentonite wall when the hole;

2、After drawing the hole, remove the hole drill, level the site to ensure the stability of the MJS rig (the steel plate should be laid when the site conditions are not met), align the drill at the center of the pile according to the requirements, and adjust the level with the support leg;

3、The crane lifts the drill bit and holds the power head, and seals the nozzle and suction nozzle with tape (prevent the nozzle and suction nozzle from being blocked during the drilling process. The tape is recommended to use the easy to break type), and then connect the drill rod in turn (pay attention to each joint sealing ring and sensor wire joint when connecting the drill rod), install the shunt after the required depth, and then connect the slurry pipe, gas pipe and water pipe to the shunt;

4、Open the background air compressor and high pressure pump grouting pump (230 high pressure grouting pump will pre-cut the bottom of the pile with clean water first, and change to cement slurry after 5 minutes)

Pulp pressure is 40 mpa, pre-cut water pressure is 25~30 mpa, pressure is 0.9~1.0 mpa, reverse slurry water pressure is 10~15 mpa, rotary speed is 3 r/min, and lifting speed is 2.5cm / min

During construction, pay attention to the change of rotary pressure and ground pressure ① to prevent drilling; ② bad reverse slurry and high ground pressure will lead to formation disturbance; good reverse slurry and low ground pressure will lead to hole collapse drilling

The normal situation is: the hole has pulp and not excessive                

—— Anman Drilling Rig sales service: Lu Xinke