In deep underground engineering, the delayed catastrophic failure of structural planes in anchored rockmass during slip is a common type of disaster. This phenomenon results from continuous fracturing in damaged rockmass, triggered by frequent excavation-induced stress waves. However, the disturbance-induced failure mechanisms of the anchored rockmass remain unclear. To address this, a custom-designed true triaxial shear test apparatus was employed to conduct a series of true triaxial disturbance shear tests on anchored slate under varying lateral and normal stress conditions. The study systematically examined the shear strength, deformation behavior, fracture surface morphology, anchor rod deformation characteristics, and the fracture damage evolution process, with a detailed analysis based on acoustic emission data. Under different lateral and normal stress conditions, the macroscopic deformation of the anchored slate, particularly during anchor failure, exhibited an "S"-shaped profile. The degree of anchor rod bending under shear was observed to slightly increase with higher shear strength and deformation. With increasing lateral stress σₚ, the disturbance-induced critical shear strength τc and shear failure stress τₚ of both anchored and unanchored slate initially showed a significant increase, followed by a gradual decline. The τc under disturbance peaked at the lateral stress of 5 MPa, where it increased by 18.75%. The roughness of the fracture surfaces in anchored slate exhibited a similar trend, with a maximum IEH at σₚ = 5 MPa, increasing by 9.1% compared to σₚ = 0 MPa. However, at σₚ = 35 MPa, the IEH decreased by 10.81% relative to its peak value. As normal stress σₙ increased, the disturbance-induced τc and τₚ showed a near-linear significant increase. When normal stress rose from 5 to 25 MPa, τc increased by 101.1%. The wear of the joints intensified, and the IEH of the shear fracture surface IEH decreased significantly, reaching a minimum of 17.5% at σₙ = 25 MPa. The degree of anchor rod bending under shear failure exhibited a slight increasing trend. In the process of disturbance shearing, the fluctuation of the b-value and lgN/b showed a decreasing trend. Furthermore, the study discussed the enhanced shear strength benefits of anchored slate compared to unanchored slate.

Lateral and Normal Stress Effects of Anchored Slate Structural Planes Under True Triaxial Disturbance Shear

期刊论文
发表日期：

2026年2月6日

查看全文

Zhi Zheng,
Xiangmeng Meng,
Yuanyuan Shen,
Haibin Feng,
Xiaohua Huang,
Kexun Zheng,
Dingping Xu

摘要

In deep underground engineering, the delayed catastrophic failure of structural planes in anchored rockmass during slip is a common type of disaster. This phenomenon results from continuous fracturing in damaged rockmass, triggered by frequent excavation-induced stress waves. However, the disturbance-induced failure mechanisms of the anchored rockmass remain unclear. To address this, a custom-designed true triaxial shear test apparatus was employed to conduct a series of true triaxial disturbance shear tests on anchored slate under varying lateral and normal stress conditions. The study systematically examined the shear strength, deformation behavior, fracture surface morphology, anchor rod deformation characteristics, and the fracture damage evolution process, with a detailed analysis based on acoustic emission data. Under different lateral and normal stress conditions, the macroscopic deformation of the anchored slate, particularly during anchor failure, exhibited an "S"-shaped profile. The degree of anchor rod bending under shear was observed to slightly increase with higher shear strength and deformation. With increasing lateral stress σₚ, the disturbance-induced critical shear strength τ_c and shear failure stress τₚ of both anchored and unanchored slate initially showed a significant increase, followed by a gradual decline. The τ_c under disturbance peaked at the lateral stress of 5 MPa, where it increased by 18.75%. The roughness of the fracture surfaces in anchored slate exhibited a similar trend, with a maximum I_EH at σₚ = 5 MPa, increasing by 9.1% compared to σₚ = 0 MPa. However, at σₚ = 35 MPa, the I_EH decreased by 10.81% relative to its peak value. As normal stress σₙ increased, the disturbance-induced τ_c and τₚ showed a near-linear significant increase. When normal stress rose from 5 to 25 MPa, τ_c increased by 101.1%. The wear of the joints intensified, and the I_EH of the shear fracture surface I_EH decreased significantly, reaching a minimum of 17.5% at σₙ = 25 MPa. The degree of anchor rod bending under shear failure exhibited a slight increasing trend. In the process of disturbance shearing, the fluctuation of the b-value and lgN/b showed a decreasing trend. Furthermore, the study discussed the enhanced shear strength benefits of anchored slate compared to unanchored slate.