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Test Method for Mode II Fracture Toughness of Rocks

A technology of fracture toughness and testing method, applied in the field of geotechnical engineering, can solve the problems of large gap, large tensile stress at the crack tip, complicated processing of loading molds, etc., and achieve the effects of convenient production, simple and reasonable structure, and simple operation.

Inactive Publication Date: 2018-12-04
吴礼舟
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Problems solved by technology

[0005] The purpose of the present invention is to provide a rock type II fracture toughness test method with convenient operation, simple loading mold and rock sample processing, and high testing efficiency, which can effectively solve the cumbersome testing of the original shear cell test, complex loading mold processing, and theoretical model problems. There is a large gap between the load and the load on the actual loading model, and the load asymmetry causes a large tensile stress at the crack tip

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  • Test Method for Mode II Fracture Toughness of Rocks
  • Test Method for Mode II Fracture Toughness of Rocks
  • Test Method for Mode II Fracture Toughness of Rocks

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specific Embodiment approach

[0025] The specific implementation method comprises the following steps:

[0026] 1. First, the rock sample to be tested is made into a 50mm×50mm×50mm square sample according to the "Engineering Rock Mass Test Method Standard", and the rock surface around the test body needs to be processed and leveled.

[0027] 2. Use milling machines, diamond saw blades and other tools to process double-sided symmetrical prefabricated straight cracks on block rock samples. The crack width is required to be less than or equal to 1.0mm, and the crack length is processed according to the planned design length. The two crack ends use a diamond saw less than 0.3mm For rocks with different strengths, the dimensionless length (a / w) must be greater than a certain value, otherwise the rock sample will be crushed.

[0028] 3. Place the square rock sample with double-sided prefabricated straight cracks between two steel loading molds, the cracks form a 45° angle of loading, and the entire test model is...

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Abstract

The invention relates to a new rock II-type fracture toughness test method. According to the invention, on the basis of an original shear box test, by means of adjustments of the stress state of a loaded mould and arrangement of a sample to eliminate rotation tendency of the sample, generation of an excessive tensile stress on a crack tip is inhibited, thereby achieving rock II-type fracture toughness test. A test model includes a square rock sample and two steel loading moulds. Straight cracks are pre-formed on the middle parts of the two sides of the square rock sample, wherein the lengths and the widths of the two straight cracks are equal to each other. The two straight cracks are arranged symmetrically. The loading moulds can achieve 45-degree loading of the sample with a loading end surface being flat and smooth. The widths of two contact surfaces between the loading moulds and the square rock sample are both half of the side length of the sample. An upper end and a lower end of the whole system are subjected to a uniform load. The method enables processing of the rock sample and the loading moulds to be more convenient, is simplified in test process, ensures accuracy of test data, is suitable for the II-type fracture toughness test of various rocks, and provides basis for researching the II-type fracture of rocks and a problem of composite fracture mainly comprising II-type fracture.

Description

Technical field: [0001] The invention relates to a method for testing rock type II fracture toughness. A shear fracture test is performed on a block rock sample on a conventional loading instrument to measure the type II fracture toughness of the rock. It belongs to the technical field of geotechnical engineering. Background technique: [0002] At present, for the tensile-shear composite cracks, the I-mode fracture toughness is mostly used to judge whether the cracked rock is damaged or not. For the compression-shear composite cracks, the results obtained using the I-mode fracture toughness as the failure criterion are different from the test results. is relatively large, which shows that this method is not applicable to the failure of composite compression-shear cracks, so it is very important to introduce mode II fracture toughness in the failure criterion of composite compression-shear cracks. [0003] So far, scholars at home and abroad have made a series of exploration...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/24G01N1/28
Inventor 吴礼舟李佳壕李滨锷李部刘果果
Owner 吴礼舟
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