Test device and test method for critical seepage air pressure of soil in saturated strata under three-dimensional stress

Abstract

The invention discloses a test device and test method for the critical seepage air pressure of the tunnel face soil in a saturated formation under three-dimensional stress, including a sample saturation unit, a critical seepage air pressure test unit, an axial pressure simulation unit, and a radial confining pressure test unit. analog unit. The device can accurately test the critical seepage pressure of the soil with different void ratios on the face of the saturated stratum under different three-dimensional stresses and the quantitative relationship between the seepage pressure and the gas loss rate, so as to provide a basis for shield tunneling in the saturated stratum. The construction of pressure tool change provides reliable key test data and basis. On the premise of effectively ensuring the stability of the face, the construction cost is reduced, the construction progress is provided, and the construction safety is ensured.

Description

technical field [0001] The invention relates to a test device and a test method for the critical seepage air pressure of the tunnel face soil in a saturated formation under three-dimensional stress. Background technique [0002] During the tunnel construction process through the shield method through the water-saturated stratum, with the continuous wear of the shield cutter, the excavation efficiency is continuously reduced, and the cutter needs to be replaced. If the tool is changed under normal pressure, the tunnel surface is prone to instability and damage under the joint action of water pressure and earth pressure, which seriously endangers the safety of tool change workers and affects the construction process. The pressurized tool change technology uses an air compressor to pressurize the air and inject it into the pressure-stabilizing cabin, so that the air pressure and the soil pressure in the cabin are dynamically balanced, and at the same time, the soil in the cabin...

AI Technical Summary

Problems solved by technology

At present, the main problems of the relevant test equipment for simulating tool change under pressure are (1) The test cannot realize the saturation of the sample and the subsequent measurement of the infiltration pressure through the same device. In the test equipment, many unnecessary artificial disturbances will be caused to the original sample, resulting in structural damage of the sample, making the test results inaccurate; , the confining pressure will also increase and cannot be quantitatively controlled. In the test, the soil mass will change with the gas entering, and the soil confining pressure will also change. These are quite different from the actual environment of tool change under pressure, and cannot be truly simulated. The three-dimensional stress state and the water-air two-phase flow process of the soil in the actual environment cause distortion of the test results

[0003] Therefore, if the test results of permeation pressure and gas loss rate obtained by the original test equipment are directly used in the tool change construction of the shield tunnel under pressure, or the air pressure is lower than the actual required air pressure, resulting in a large amount of groundwater gushing out, seriously affecting the tunnel face and support. The stability of the protective structure endangers the safety of tool changers and seriously affects the construction progress; or the air pressure is greater than the actual required air pressure, which greatly increases the difficulty of tool change under pressure, construction costs, and reduces the construction speed. Health will also have a serious impact; even if the air pressure is close to the actual required value, the inaccurate prediction of the gas loss rate will greatly increase the construction cost and endanger the safety of personnel who change tools under pressure

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