Construction technology for dewatering wells in well drilling projects

Design scheme for foundation pit dewatering

⑴ Well layout

52 pipe wells - along the east area of Block 0, namely C and D - arranged around the foundation pit with a center distance of 1.50m from the edge of the pit. The average distance between the wells is about 9.0m. The water collection main pipe is connected to a 100mm diameter steel pipe and a 50mm diameter pumping pipe. The water collection main pipe at the entrance of the horse road should be buried to prevent damage caused by wheel rolling.

⑵ Pipe well structure

The burial depth of the pipe well is 27.0m, the diameter of the wellbore is 600mm, and the diameter of the sand free cement pipe is 400mm

The pores between the well casing and the wellbore shall be filled according to the following requirements. The upper 2.0m shall be filled with clay and sealed tightly. The area below 2.0m shall be filled with 2-4mm granules. The area below 10.0m shall be filled with 6-8mm granules until the bottom of the well. The filter tube shall be wrapped with lead wire and securely wrapped with nylon cloth or 80 mesh wire mesh.

Construction Plan for Precipitation Well

Setting out and positioning the well - drilling rig in place and drilling - lifting and lowering the well pipe - filling the filter material

Install the drainage main pipe, wash the well, test and pump water normally.

2.2 Construction sequence

⑴ Set out and locate the well.

⑵ Layout and drill holes to the design depth.

⑶ Install a φ 400 sand free filter tube or bridge filter tube (there are various other types of well tubes, such as steel cage, UPV C, etc.).

The bottom sealing joint of the well casing should be firmly secured to prevent sand backflow.

Fill the filter material between the hole wall and the sand pipe within a certain range close to the wellhead (usually in the filling area) and seal it tightly with clay.

Wash the well of the air compressor until the water is clear.

⑺ Submersible pump (inlet) should be sunk to a depth of 2.0m at the bottom of the well, and a water collection main pipe should be laid to connect the pump with a pumping pipe.

(8) Test pumping to check if the well pipe is leaking and if the water pump is reversing.

Measure the initial water level and flow rate of each well for formal pumping.

Normal pumping monitoring.

2.3 Quality Control

⑴ The sand free filter water pipe must be unobstructed, the particle size of the filter material should be uniform, and the mud content should be low. They should all be inspected and qualified before use.

Strictly control the wellbore diameter, depth, and spacing according to the design requirements.

The interface of the sand free cement pipe must be tightly sealed with plastic cloth.

⑷ Quality inspection and acceptance shall be carried out for each drilled well - aperture deviation ≤ 10cm, vertical deviation ≤ 5, well depth deviation ≤ 20cm.

After washing the well, the mud and sand content should be controlled within 10.

During the pumping period, the pumping pipes and pumps should be checked regularly for any faults. If any are found, they should be repaired or replaced in a timely manner, and the pumping situation should be checked regularly to prevent water from burning out the pumps and affecting the precipitation effect.

A dedicated person must be responsible for all well drilling and pumping processes, and well completion and pumping records must be kept to ensure the quality of well completion and normal pumping.