Testing method for measuring unloading strength of fractured rock

Abstract

A testing method for measuring the unloading strength of a fractured rock comprises the following steps that firstly, core boring sampling is performed on a rock mass, a deformation measurement device is installed on a test piece, and the test piece is placed in a tri-axial test cylinder; secondly, the axial displacement of the test piece keeps unchanged, confining pressure is exerted to reach a design value, afterwards, the confining pressure keeps unchanged, axial pressure is exerted to reach a design value; thirdly, the axial displacement of the test piece keeps unchanged, the confining pressure is decreased gradually according to a design unloading rate until the confining pressure reaches an axial pressure sudden-change control point, and the axial pressure and the confining pressure, corresponding to the sudden-change control point, of the test piece are recorded; fourthly, the axial displacement of the test piece keeps unchanged, the confining pressure is restored to an initial design value according to a design loading rate, afterwards, the confining pressure keeps unchanged again, and the axial displacement of the test piece is increased to the next design value according to the design loading rate; fifthly, the processes of unloading fracture, confining pressure restoration and axial pressure increase are repeated, the unloading fracture strengths of the axial pressure sudden-change point, corresponding to different confining pressures, of the test piece are obtained; sixthly, the mechanical parameters of the unloading facture strengths are obtained through data fitting.

Description

technical field [0001] The invention relates to a test method for rock unloading strength, in particular to a test method for measuring the unloading strength of cracked rocks. Background technique [0002] With the vigorous development of national infrastructure construction, the excavation depth of rock engineering continues to increase. For example, the diversion tunnel of Jinping Hydropower Station has a buried depth of 2525m, and the mining depth of Huainan Coal Mine has reached 1200m. The increase in buried depth has significantly increased the stress of the surrounding rock , and rock bursts, landslides, large deformations and other engineering geological disasters often occur, and many damaged tunnel (roadway) surrounding rocks will still be damaged after repair and reinforcement, which brings difficulties and difficulties to the safe construction of rock engineering. challenge. The deep rock engineering is obviously different from the shallow rock engineering: the ...

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Problems solved by technology

In addition, due to rock defects and human factors, unloading test data often have singular or even wrong values, and supplementary tests are required, which increases the workload of the experiment, and the unloading strength obtained by this series of experiments is only the peak strength of the intact rock. It cannot correctly characterize the unloading and re-destruction strength of the fractured rock, and there is an essential difference between the two

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