Self-centering double shear test device and type II fracture toughness test method

Abstract

The invention discloses a self-centering double shear test device which comprises a sample box.A horizontal through hole and a vertical through hole are formed in the sample box and are orthogonal.A first normal pressing block and a second normal pressing block are arranged at the two ends of the horizontal through hole respectively.The first normal pressing block abuts against one end of a position adjusting rod, and the other end of the position adjusting rod is connected with a threaded hole in a first counter-force support through a thread.The second normal pressing block abuts against a normal force loading device which is arranged on a second counter-force support.The first counter-force support and the second counter-force support are connected through a horizontal dowel bar.The invention further discloses a rock sample shear strength parameter test method and a type II fracture toughness test method.The self-centering double shear test device is simple in structure, easy to manufacture and high in applicability, has a self-balancing function, can be easily combined with an existing rock mechanical test system, and can be used for carrying out a rock type II fracture toughness test.

Description

technical field [0001] The invention relates to the field of rock mechanics tests, in particular to a self-centering double-sided shear test device, and also to a type II fracture toughness test method, which is mainly used for indoor rock double-side shear and type II fracture toughness tests. Background technique [0002] In the field of geotechnical engineering, it is usually through rock mechanics experiments to understand the mechanical properties, deformation and failure laws of rocks and rock masses, as well as various physical and mechanical effects caused by various structures on rock masses. Construction provides the required parameters. At present, rock laboratory tests mainly include uniaxial test, triaxial test, shear resistance test, etc., and rock mechanical parameters and strength indexes are obtained through these tests. [0003] At present, there are many equipment for uniaxial test and triaxial test, and the tonnage is generally relatively large. There ar...

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Problems solved by technology

[0003] At present, there are many equipment for uniaxial test and triaxial test, and the tonnage is generally relatively large. There are few equipment capable of performing shear test. Shear test is divided into single-sided shear test and double-sided shear test. Most of the equipment is used for single-sided shear tests, which are used to study the mechanical properties of rock joint surface slippage, concrete strength, etc. Such equipment generally has a small horizontal thrust loading tonnage and is used for tests on rock masses with low strength It is suitable, but for higher strength hard rock, especially for large-scale hard rock samples, the tonnage is often not enough, resulting in the continuous shearing of rock samples

A small number of equipment that can carry out double-sided shear tests often have a major defect: the test equipment does not have the function of applying normal force, and can only carry out shear tests with zero normal force, so the obtained strength parameters are limited. Only the shear strength of the rock can be obtained, but the cohesion and internal friction angle of the rock cannot be given

In addition, rock type II fracture toughness is a very important parameter in rock mass engineering, which characterizes the ability of rock to resist shear fracture. Type II fracture means that the direction of crack expansion under the action of external force is still in the crack plane, and the tip of the crack slips and displaces. Parallel to the fracture plane, the displacement of the opening of the fracture tip is zero. At present, there are few reports on the test of rock mode II fracture toughness, and most methods cannot avoid the occurrence of additional non-negligible crack extension in the test.

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