JRMGE / Vol 15 / Issue 6

Article

Experimental investigation on frictional properties of stressed basalt fractures

Zhen Zhong, Congqiang Xu, Lei Wang, Yunjin Hu, Fengshou Zhang

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a School of Civil Engineering, Shaoxing University, Shaoxing, 312000, China
b Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province, Shaoxing University, Shaoxing, 312000, China
c Department of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai, 200092, China
d Key Laboratory of Geotechnical & Underground Engineering of Ministry of Education, Tongji University, Shanghai, 200092, China


2023, 15(6): 1457-1475. doi:10.1016/j.jrmge.2022.12.020


Received: 2022-05-25 / Revised: 2022-10-18 / Accepted: 2022-12-07 / Available online: 2023-02-10

2023, 15(6): 1457-1475.

doi:10.1016/j.jrmge.2022.12.020


Received: 2022-05-25

Revised: 2022-10-18

Accepted: 2022-12-07

Available online: 2023-02-10


Abstract:

The frictional strength and sliding stability of faults are crucial in interpreting earthquake mechanisms and cycles. Herein, we report friction experiments on basalt fractures, using a self-designed triaxial apparatus that allows direct shear of samples under coupled hydro-mechanical conditions. Velocity-stepping (VS) and slide-hold-slide (SHS) experiments are performed on both bare and gouge-bearing surfaces of Xiashan basalt subjected to cyclic shear velocities at 1–30 μm/s, effective normal stresses of 1–5 MPa, and pore pressures of 70–300 kPa. The measured basalt friction coefficients are in the range of 0.67–0.74, which is sensitive to gouge thickness, normal stress, and water. Specifically, a reduction in friction coefficient is observed with an increment in gouge thickness, normal stress, and pore pressure. Based on the microscopic observation of the pre- and post-shearing sliding surfaces, this weakening effect in friction coefficient can be attributed to powder lubrication. Furthermore, the VS test results reveal predominantly velocity-strengthening behavior at investigated slip velocities, and this velocity strengthening behavior does not appear to be influenced by variations in normal stress, gouge thickness, and water. However, changes in sliding velocity and normal stress can lead to a shift between stable and unstable sliding. Specifically, stable sliding is favored by high sliding velocities and low normal stress applied in this study. Finally, we analyze the experimental data by calculating the rate-and-state parameters using the rate- and state-dependent friction (RSF) theory. Importantly, the calculated friction rate parameter (a-b) supports the velocity-strengthening behavior. Both frictional relaxation (Δμc) during hold periods and frictional healing (Δμ) upon re-shearing are linearly proportional to the logarithmic hold time, which may be attributed to the growth in true contact area with hold time. This study sheds light on the roles of sliding velocity, and gouge thickness in controlling frictional strength and stability of basalt fractures.

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Keywords: Rock friction, Basalt fracture, Gouge, Velocity-strengthening behavior, Frictional healing

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Zhen Zhong, Congqiang Xu, Lei Wang, Yunjin Hu, Fengshou Zhang, 2023. Experimental investigation on frictional properties of stressed basalt fractures. J. Rock Mech. Geotech. Eng. 15 (6), 1457-1475.

Author(s) Information

Zhen Zhong

Dr. Zhen Zhong is an associate professor in School of Civil Engineering of Shaoxing University. He obtained his BSc degree in Hydraulic Engineering from South China University of Technology in 2009, and received his PhD degree in Hydraulic Structural Engineering from Zhejiang University in 2014. He has been involved in research and teaching in Geotechnical Engineering for over 10 years. His research interest is rock mechanics and fault mechanics, with a special focus on the characterization of hydromechanical properties of fractured rock under thermo-hydro-mechanical-chemical (THMC) coupling conditions. He is author of over 30 peer review papers. He is reviewer for some international journals, such as Bulletin of Geology Engineering and Environment, Geomechanics and Geophysics for Geo-Energy and Geo-Resources, Environmental Earth Sciences.