Crack closing stress determination method based on axial stress response

Abstract

The invention discloses a crack closing stress determination method based on axial stress response. The method comprises the following steps: establishing a curve graph corresponding to an axial strain-axial stress relation of a rock sample based on a test data point set; selecting an initial point P (epsilon p, sigma p) in a linear elasticity stage of a curve graph corresponding to the axial strain-axial stress relationship of the rock sample; acquiring the slope of a connecting line of two points between each test data point (epsilon i, sigma i) and the initial point P (epsilon p, sigma p); obtaining an elastic modulus E; obtaining a reference straight line sigma = E epsilon corresponding to axial strain-axial stress; establishing a curve graph corresponding to axial strain-axial stress difference; and obtaining an inflection point in the curve graph corresponding to the axial strain-axial stress difference, wherein the axial stress corresponding to the inflection point is the crack closing stress sigma cc. According to the method, the problem in determining the compaction point is effectively solved, the accuracy of obtaining the crack closing stress sigma cc is remarkably improved, and the influence of man-made subjective assume on the crack closing stress in an existing method is eliminated.

Description

technical field [0001] The invention relates to the technical field of engineering structures, in particular to a method for determining crack closure stress based on axial stress response. Background technique [0002] Affected by complex geological structures and environmental factors such as excavation disturbances, earthquakes, and microseisms, natural rock materials contain more or less primary microscopic microcracks. Initiation, extension, and penetration are closely related [1,2] , it is of great significance to study the corresponding characteristics between microcrack development and macroscopic stress threshold for the stability evaluation of deep tunnels, underground storages and other underground projects. [0003] The mechanical properties of rocks under compression have been extensively studied over the past 60 years [3] . Generally speaking, if figure 1 As shown, there are four key stress thresholds in the process of rock compression failure, that is, the...

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Problems solved by technology

[0007] Currently, the crack closure stress (σ cc ) determination of the International Society of Rock Mechanics (ISRM) has not yet formed a unified method, the reliability of the existing methods for the obtained stress threshold is inconclusive, and it is urgent to propose a new objective determination method

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