Abstract:

Although dynamic shearing properties of rock discontinuities are of great importance in many rock engineering applications, it is very rare to see dynamic shear tests on rock discontinuities. The author describes static, cyclic, one-way and two-ways dynamic shearing experiments on various natural rock discontinuities and saw-cut planes and discusses the shear strength characteristics obtained from the different testing techniques and interrelations. The experiments clearly showed that the dynamic shear behavior of discontinuities are very complex and anisotropic. Nevertheless, this study provides some fundamental understanding on the static and dynamic behavior of rock discontinuities and their correlation with each other.

1 Introduction

Dynamic shearing properties of rock discontinuities are of great importance in many rock engineering applications (Aydan et al. 2011). Nevertheless, dynamic shear tests on rock discontinuities are very rare. In this study, the author describes static, cyclic, one-way and two-ways dynamic shearing experiments on various natural rock discontinuities and saw-cut planes. Natural rock discontinuities involve schistosity planes in quartzite, green-schist, cooling planes in andesite, saw-cut planes of Ryukyu limestone, Motobu limestone, andesite and basalt from Mt. Fuji, dolomite from Kita-Daitojima, granodiorite from Ishigaki and Inada granite and Oya-tuff.

The experiments clearly showed that the dynamic shear behavior of discontinuities are very complex and anisotropic (Aydan et al. 1996). Furthermore, the degradation of roughness of the discontinuity planes results in further complexity in regard with modeling shear behavior under dynamic conditions. Nevertheless, the dynamic response at the first full cycle provides a basis for the overall dynamic shear behavior of discontinuities. and interfaces. Unpolished saw-cut planes of rocks should never be used for evaluating their shear responses under dynamic conditions in the first step (Aydan 2016). The dynamic shear behavior of actual discontinuities should be carried out as the next step.

The experimental results are compared with those from static and one-way dynamic shearing experiments and their implications in practice are discussed. Although more experiments are necessary for the selection of appropriate dynamic loading pattern with the consideration possible loading conditions in-situ, this study provides some fundamental understanding on the static and dynamic behavior of rock discontinuities and their correlation with each other.

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