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Rock type-I fracture crack speed and fractal dimension determination method

A technology of crack growth speed and crack growth, which is applied in the field of measurement of rock type I fracture crack growth speed and fractal dimension, which can solve the problems of inaccurate measurement methods and achieve the effect of saving test costs

Inactive Publication Date: 2019-05-10
HENAN POLYTECHNIC UNIV
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Problems solved by technology

[0004] The object of the present invention is to provide a method for measuring the growth rate and fractal dimension of a rock I-type fracture crack, which is easy to operate and can accurately reflect the speed and fractal characteristics of crack growth in rocks, overcoming the previous rock material Type I crack growth measurement. The method is not accurate enough

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  • Rock type-I fracture crack speed and fractal dimension determination method
  • Rock type-I fracture crack speed and fractal dimension determination method
  • Rock type-I fracture crack speed and fractal dimension determination method

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Embodiment 1

[0043] Method for determining the fractal dimension and growth velocity of mode I crack growth in dynamic fracture of rock materials.

[0044] Choose the rock material sample with straight cutting groove and semicircle bending. The rock material is drilled through a cylindrical core with a diameter of 50mm, cut and polished into a 25mm disc sample, and the unevenness of both ends is ±0.05mm after grinding, and the end face is vertical axis, the maximum deviation is not more than 0.25°; then each disc sample is cut into two half-disc samples along the diameter, and a diamond circular saw blade with a thickness of 0.3mm is used in the middle of the half-disc sample to obtain a straight cut groove , and using a diamond wire saw with a thickness of 0.1mm to make the crack tip, the final geometry is as figure 1 shown. Load the sample according to the loading method described in step b in the "Specific Implementation Methods" of this patent application. The observation of cracks d...

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Abstract

The invention discloses a rock type-I fracture crack speed and fractal dimension determination method. The method is characterized by, to begin with, selecting a straight cutting groove semicircle bending rock material test sample, which is finally formed by core drilling, cutting grinding and cutting groove prefabricating; then, testing the test sample through a three-point bending mode; througha high-speed camera, observing and recording crack growth forms in the sample loading fracture process, and collecting a voltage-time curve recorded by a strain gauge on an SHPB pressure bar in the test process and the crack growth process of each test sample recorded by the high-speed camera, and saving the recorded images as a file; and finally, processing the images recorded by the high-speed camera, calculating crack growth interval time and distance through Image J image processing software, calculating crack speed and acceleration speed through derivation, and furthermore, carrying out fitting to obtain fractal dimension of crack growth according to a box-counting dimension method and a least square method.

Description

technical field [0001] The invention relates to the field of rock material test methods, in particular to a method for measuring the growth rate and fractal dimension of rock I-type fracture cracks. Background technique [0002] As the product of the formation of the earth and the evolution of crustal geological activities, rocks are widely used in various engineering construction fields such as building foundations, surrounding rocks or building materials. However, the instability and destruction of rock engineering are mostly caused by the initiation of cracks inside the rock mass and their expansion and penetration. Accurate determination of crack propagation velocity and fractal dimension of rock under dynamic load is of great significance for rock blasting engineering, earthquake research, hydraulic fracturing extraction of coalbed methane, and rock failure mechanism research. Among the three fracture modes of rock, type I (open type) fracture is the most common in eng...

Claims

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Application Information

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IPC IPC(8): G01N3/36G01N3/06
Inventor 龚爽孟祥燕王浩杨达明潘坤周礼鸿
Owner HENAN POLYTECHNIC UNIV
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