Experimental Study on Mechanical Properties and Cracking Behaviors of T-Shaped Flaw-Contained Rock-like Materials Under Cyclic Loading

Lan Cui,Yi Liu,Qian Sheng,Ping Xiao

doi:10.3389/feart.2021.768077

Abstract

Geotechnical hazards such as debris flows, rock falls in slopes, rock collapse, and rockburst in underground mining or caverns are tightly correlated to the mechanical behavior of natural rock mass stability. Strength and failure mode of the natural rock mass are governed by the presented fissures. In this paper, samples containing T-shaped fissures with different geometry were prepared by rock-like materials and tested under varying uniaxial cyclic loading compression. The effect of T-shaped fissures with different geometry and the strain rate and loading frequency on the strength of tested samples were studied, and the failure mode of the samples containing T-shaped cross fissures under different working conditions was observed. The results show that the function of the minor fissures was not completely negative, and the strength of T-shaped fissure samples containing a major fissure with different inclination angles presented a varying trend with the increasing included angle between the major and minor fissures. Moreover, the strength of the cracked samples increased with the increase of the strain rate and loading frequency, and the larger the included angles between the major and minor fissures, the more sensitive the T-shaped fissure sample was to the change of frequency, but without a noticeable linear correlation relationship between the strength of the sample and the included angles between the major and minor fissures. In addition, the existence of the minor fissures had a significant impact on the failure mode of the sample, and the failure mode of the samples containing T-shaped cross fissures of the same geometry under the uniaxial compression and the uniaxial cyclic load was equivalent.

Highlights

Geotechnical hazards indicate geological or environmental processes, phenomena, and conditions that are potentially dangerous or pose a level of threat to human life, health, and property, or to the environment
Unconfined and biaxial compression tests on samples containing multiple fissures were conducted by Lin et al (2000), the results showed that the failure mode and peak strength of the cracked sample were diverse due to the variation of the number and length of prefabricated fissures and the length of rock bridge and the size of lateral pressure, respectively
The purpose of this work was to explore the effect of strain rate, loading frequency, and geometric characteristics of T-shaped fissures on the strength and failure mode of the samples, which can be applied as a guide in practical application of rock engineering

Summary

Introduction

Geotechnical hazards indicate geological or environmental processes, phenomena, and conditions that are potentially dangerous or pose a level of threat to human life, health, and property, or to the environment. Geotechnical hazards such as debris flows, rock falls in slopes, rock collapse, and rockburst in underground mining or caverns are tightly correlated to the mechanical behavior of rock mass stability (e.g., Huang et al, 2020; Huang et al, 2021). Some researchers have prepared rock-like samples by cement mortar or gypsum (e.g., Bobet and Einstein, 1998; Wang et al, 2018), other researchers cut the required fissures on real rock to get closer to the real rock mass (e.g., Ingraffea and Heuze, 1980; Huang et al, 1990; Liu et al, 2019)

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