(1. College of Civil Engineering, Guilin University of Technology, Guilin, Guangxi 541004, China; 2. State Key Laboratory of Geomechanics and Geotechnical Engineering Safety, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences,
Wuhan, Hubei 430071, China)
Abstract：The frictional slip behavior of faults is influenced by various factors, with the stiffness of the fault and the surrounding rock mass playing a pivotal role in determining the mechanical behavior patterns of fault slip. In laboratory experiments, the controlled simulation of fault frictional behavior through the adjustment of shear loading stiffness is an essential approach to investigate the associated mechanical characteristics and underlying mechanisms. However, effective methods for regulating shear loading stiffness during experiments are currently lacking. To address this challenge, the study systematically analyzes the variation of shear loading stiffness in experimental apparatus under various external conditions employing both direct and indirect testing methods. A regulation method is proposed, which involves connecting elastic blocks in series with the apparatus to adjust its shear loading stiffness. The experimental investigation of fault frictional behavior under varying shear loading stiffness conditions yields the following findings: (1) the shear loading stiffness of the apparatus is not constant; it generally increases with rising shear force and exhibits significant dependence on the apparatus deformation rate—it is weakly dependent during the initial and final loading stages but strongly dependent during the intermediate stage; (2) Materials PA, POM, and ABS demonstrate favorable linear elastic properties within a certain loading range and can be used as elastic blocks in series to regulate the apparatus shear loading stiffness; (3) as shear loading stiffness decreases, the stick-slip period, unstable slip displacement increment, unstable slip velocity, shear force drop, and fault stiffness all show increasing trends, while the viscous slip velocity gradually decreases; (4) the sensitivity of different stick-slip parameters to changes in shear loading stiffness varies—specifically, the stick-slip period, unstable slip displacement increment, and unstable slip velocity exhibit higher sensitivity, whereas the shear force drop, fault stiffness, and viscous slip velocity are relatively less sensitive. These findings offer important insights into the mechanical behavior of fault friction and the variation characteristics of seismic source parameters.
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2025, Vol. 44 
