Abstract

Most of the cracks in the rock masses are in a three‐dimensional (3D) state, and it is always a hot topic to reveal the mechanical mechanism of 3D crack growth. In this paper, the research on the growth behavior of 3D crack is performed through laboratory experiments and numerical simulations. Cement samples with different angles of 3D crack are prepared, and the uniaxial compression experiment is carried out. The results indicate that initiation of preexisting crack with an angle of 45° is easier and shear failure characteristics of corresponding samples are obvious. Through theoretical analysis, the preexisting crack starts to grow at the end of the short axis, along the short axis end to the long axis end of the preexisting crack, the shear effect decreases gradually, and the tearing effect increases gradually. Combined with numerical simulation, the experimental and analysis results are verified, and the preexisting crack growth process is presented. The growth direction of the preexisting crack changes from perpendicular to the crack surface to parallel principal stress direction, and the maximum growth length can reach 1.2 times the minor axis radius of the preexisting crack. The research results can provide an important theoretical basis for revealing the evolution process of the cracks in rock masses.

Highlights

  • The rock is a natural and heterogenous material, possessing various defects inside and on the surface

  • Most research simplifies the crack to 2D state due to the complexity of experimental observation and theoretical analysis of a 3D crack

  • And 7, the following can be seen: [1] Parameter KII increases monotonically with the increase of ellipse polar angle ψ, but KIII decreases monotonically with the increase of ellipse polar angle ψ. This phenomenon indicates that the shear effect of fracture mode II decreases gradually along the short axis end to the long axis end of the preexisting crack, but the tearing effect of fracture mode III increases gradually

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Summary

Introduction

The rock is a natural and heterogenous material, possessing various defects inside and on the surface These defects account for only a small part of the volume of rock, they have an important impact on the mechanical properties of the rock. Most research simplifies the crack to 2D state due to the complexity of experimental observation and theoretical analysis of a 3D crack. On this basis, a lot of experiments and research work have been carried out, and many meaningful results have been obtained [5–12]. Due to the difficulty in making the samples with 3D crack and observation, the research on the growth mechanism of crack with different inclination angles was relatively less. In this paper, cement samples with different angles of

Experiment Introduction
Experimental Results
Initiation Mechanism of Crack Tip
Numerical Simulation
Conclusions

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