Intact rock-like specimens and specimens that include a single-, planar joint and triangular sawteeth joint at various angles are prepared for split Hopkinson pressure bar (SHPB) testing at loading rates of 303.1-5,233.6 GPa/s. The effects of the loading rate and angle of the load applied to various sawteeth joint patterns on the failure type and dynamic peak stresses/strength of the specimens are investigated. Experimental results demonstrate that failure pattern can be classified into the following four types; Type A, integrated with or without tiny flake-off; Type B, slide failure; Type C, fracture failure; and Type D, crushing failure. The results of statistical analysis of variance (ANOVA) indicate that the loading rate, the angles of the base plane (β) and the asperity (α) of the sawteeth joint of the specimen all affect its dynamic peak stress when fracture failure occurs; the loading rate and β are important when the slide failure occurs; and the loading rate is the sole factor that significantly influences its dynamic peak stress when the specimen is crushed to failure.

1. Introduction

Several studies of the static influences of discontinuities on rock engineering have been conducted, most current research in the field of rock dynamics concentrate on intact rock, including the influence of loading rate on strength, crack initiation and propagation (Xia et al., 2017; Dai et al., 2016). Improvements in measurement equipment and technology have led to a wide range of investigations of the dynamic characteristic of intact rock specimens at different loading rates using power test instruments such as MTS-810 and Split Hopkinson Pressure Bar (SHPB) (Xia and Yao, 2015; Zhang and Zhao, 2014), but experimental studies and simulations of rock discontinuities are few.

In this study, a series of intact rock-like specimens and specimens that contain a single-, smooth planar joint and triangular sawteeth joint at various angles are prepared for SHPB testing. The failure type of each specimen and the dynamic peak stresses under various loading rates are determined experimentally, and the effects of loading rate, angle of application of load on various sawteeth joint patterns are investigated to elucidate the engineering characteristics of a rock mass under dynamic impact.

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