ABSTRACT
The authors have developed a new dynamic direct shear test machine, for the purpose of investigating the response to the earthquake motion of rock discontinuities. We conducted a large number of dynamic direct shear tests for the rock discontinuities. Test specimens are Limestone joint, Sandstone joint and Mudstone bedding plane of natural discontinuity made by boring-core, and artificial discontinuities made of mortar. By these test results, we examined dynamic shear strength and dynamic shear deformability of rock discontinuity.
The authors defined dynamic peak shear strengthτp(d), by the results of Multi-stage amplitude dynamic direct shear tests. Then, we investigated comparison of dynamic shear strength and static shear strength, and dependence on frequency for dynamic shear strength. It is clear that dynamic shear strength exceeds static shear strength for relatively rough planes, and dynamic peak shear strengthτp(d) does not depend on the frequency in the range from 0.1Hz to 3.0Hz
Also we defined the dynamic diagonal shear stiffness Ksd(d) and attenuation h. Furthermore, we examine the stress dependence and frequency dependence of these dynamic deformability parameters. We defined skelton curves and modelled it by hyperbolic function. It is Clear that both the dynamic diagonal shear stiffness Ksd(d) and attenuation h, have a dependance about normal stress σn and shear stress amplitude.
