Abstract
The presence of gouge in rock joints significantly affects the physical and mechanical properties of the host rock mass. Wave-based exploration techniques have been widely used to investigate the effects of gouge fill on rock mass properties. Previous research on wave propagation in gouge-filled joints focused on analytical and theoretical methods. The lack of experimental methods for multiple rock joint systems, however, has limited the verification potential of the proposed models. In this study, the effects of gouge material and thickness on wave propagation in equivalent continuum jointed rocks are investigated using a quasi-static resonant column test. Gouge-filled rock specimens are simulated using stacked granite rock discs. Sand and clay gouge fills of 2 and 5 mm thicknesses are tested to investigate the effects of gouge material and thickness. Comprehensive analyses of the effects of gouge thickness are conducted using homogeneous isotropic acetal gouge fills of known thickness. The results show that gouge fill leads to changes in wave velocity, which depend on the characteristics of the gouge fill. The results also show that particulate soil gouge is susceptible to preloading effects that cause permanent changes in the soil fabric and contact geometry and that increased gouge thickness causes a more significant stiffness contribution of the gouge material properties to the overall stiffness of the equivalent continuum specimen. The normal and shear joint stiffnesses for different gouge fill conditions are calculated from the experimental results using the equivalent continuum model and suggested as input parameters for numerical analysis.
Highlights
The presence and nature of rock joints govern the physical behavior of rock masses and affect elastic wave propagation and attenuation [1,2,3,4]
An experimental investigation was performed on the effects of gouge material and gouge thickness on the elastic wave propagation in jointed rock specimens
Gouge fill resulted in decreased longitudinal and shear wave velocities compared with clean-cut joints owing to the decreased joint stiffness
Summary
The presence and nature of rock joints govern the physical behavior of rock masses and affect elastic wave propagation and attenuation [1,2,3,4]. Natural rock joints are filled with gouge material ranging from fluids (e.g., water or oil) to viscoelastic particulate soils (e.g., sand, silt, and clay). Prior research noted that the presence of gouge fill greatly influences the mechanical behavior and seismic response of the jointed rock mass for single and multiple joints. (2011) [13] suggested analytical solutions for wave propagation in single and multiple rock joints with viscoelastic gouge fills and conducted modified split Hopkinson pressure bar experiments on single sand-filled joints. Previous experimental studies on gouge fill joints focused on single joints, and the lack of experimental methods for testing jointed rocks with multiple joints and joint sets limits the verification potential of the proposed models
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