Method for determining implicit joint density threshold value for generation of slip-off effect in rock test

Abstract

The invention discloses a method for determining an implicit joint density threshold value for the generation of a slip-off effect in a rock test. The method comprises the following steps: (1) preparing samples with different implicit joint densities; (2) starting with the sample with minimum implicit joint density, measuring the gas permeability of the sample under the same confining pressure and different seepage pressures, recording the inlet gas pressure and the outlet gas pressure of a pressure chamber and taking an average value of the inlet gas pressure and the outlet gas pressure as average pressure; (3) drawing a change curve of the gas permeability of the sample along with the reciprocal of the average pressure and fitting the curve through a function; (4) if a fitting correlation coefficient is greater than 0.90, selecting the next sample of which the implicit joint density is greater than that of the sample and repeating the step; if the correlation coefficient is less than 0.90, the implicit joint density of the sample is the implicit joint density threshold value for the generation of the slip-off effect. The method disclosed by the invention has the benefit that the slip-off effect can be directly linked to the implicit joint density, so that the gas permeability measuring results of the samples with different implicit joint densities can be more directly and quickly evaluated.

Description

technical field [0001] The invention belongs to the engineering field of rock engineering such as underground caverns, mining, underground nuclear waste storage, water conservancy and hydropower, etc., which takes jointed rock mass as the research object. Method for joint density thresholding. Background technique [0002] When the liquid flows in the porous medium, the flow velocity of the liquid in the center of the pore channel is significantly higher than that at the pore wall, and the liquid velocity at the solid-liquid contact surface at the pore wall is almost zero. When gas flows in porous media, in addition to collisions between gas molecules, there are also collisions between gas molecules and pore walls (coupling force at the solid-gas boundary). When the rock pore radius is close to the free path of gas molecules, the gas The frequency of collisions between molecules and solid walls increases, which creates an unwanted flow at the wall surface, known as slip flo...

AI Technical Summary

Problems solved by technology

[0004] Purpose of the invention: The present invention aims at the problem that the gas permeability cannot reflect the real permeability of the sample due to the existence of the slippage effect in the prior art, and provides a method for determining the hidden joint density threshold value of the slippage effect in the rock test

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