brief introduction

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Water pressure test is a kind of in-situ test in which the water pressure is put into the borehole in a high-pressure way, and the development and permeability of rock mass fractures are known according to the calculation of water absorption of rock mass. The water pressure test is to isolate a certain length of drilling test section with a water stop device, and then use a fixed water head to press water into this section of drilling. The water seeps into the rock body through the cracks around the hole wall, and the final seepage volume will tend to a stable value. The strength of rock mass permeability can be determined according to the water pressure head, the length of the test section and the stable seepage volume. It is usually expressed in terms of water permeability q, and the unit is Lu. It is defined as: when the pressure of water pressure is 1MPa, and the water injected per meter length per minute is 1L, it is called 1Lu. Q=Q/(P * L), where q is the water permeability, Lu; Q is the pressure flow, L/min; P is the total pressure acting on the test section, MPa; L is the length of the test section.

Classification of water pressure test: simple water pressure test, single-point water pressure test and five-point water pressure test.

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1. Pre-test stage

Slowly raise the water pressure in the pipeline to the specified test pressure and stabilize it for 30min. During this period, if there is a pressure drop, water can be injected to supplement the pressure, which shall not be higher than the test pressure;

Check whether there is water leakage or damage at the pipe interface and fittings;

In case of water leakage and damage, stop the pressure test in time, find out the cause and take corresponding measures, and then retest the pressure.

2. Main test stage

Stop water injection and make up pressure, and keep it stable for 15min. When the pressure drop does not exceed the allowable pressure drop value after 15min, reduce the test pressure to the working pressure and keep it constant for 30min. Conduct visual inspection. If there is no water leakage, the hydraulic test is qualified. [1]

3, Main technical parameters:

Sealing hole diameter 30-200mm (can be processed according to user requirements)

Working pressure 1-10MPa (can be processed according to user requirements)

The working flow can be 3-4.5 tons of grouting per hour

Hole sealing depth 1-800m