Through the watertightness test of the rig pipe, understand the rig pipe wall bearing

1. Purpose of watertight test of rig conduit

Ensure that the technological process of the bridge pile foundation pouring pile operation does not affect the construction process.

2, requirements and methods

1) Make all drilling rig ducts strong, and the inner wall should be smooth, straight, smooth and free of local bumps. The inner diameter of each section of the catheter should be the same, and the deviation is not greater than ± 2mm.

2) Before using the drill rig duct and after a period of use, in addition to careful inspection of its specifications, quality and splicing structure, splicing, watertightness, and other tests are also required.

3) Connect the end of the rig's pipe with a sealing fastener. The catheter can be assembled in sections next to the borehole, and then assembled section by section when hoisting. Careful inspection should be carried out when assembling in sections, and severe deformation and wear must not be used.

4) Fill the assembled pile pipe first with 70% water, both ends are closed, and one end is welded to the air pipe joint. Enter the calculated wind pressure, and the pipe needs to be rolled several times. It will be qualified after 15 minutes without water leakage.

3. Calculation method of bearing pressure of drilling rig conduit

The water pressure in the watertight test of the concrete pipe of the cast-in-situ pile shall not be less than the pressure of 1.3 times the water depth in the wellbore. The water pressure during the pressure test shall not be less than the internal pressure Pmax that the wall of the pipe may bear. Pmax can be calculated as follows:

Pmax = 1.3 (ㄚ cHcmax- ㄚ wHw)

In the formula: Pmax——the internal pressure that the catheter wall may withstand, KPa;

ㄚ c——Concrete bulk density (with 24KN / m3), KN / m3;

CHcmax——the height of the concrete column in the duct, using the length of the duct, m;

ㄚ w——water or mud bulk density in the borehole, when the mud volume is greater than 12KN / m3, underwater concrete should not be poured, KN / m3;

Hw——water or mud depth in the borehole, m.

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