ABSTRACT:

In the construction of rock engineering, the soft rock tunnel is generally excavated using the drilling and blasting method, and thus the rock mass is subjected to dynamic loading. The fracture behavior of rock mass under dynamic loading is different from that under static loading. In order to investigate fracture behaviour of sandy mudstone subjected to dynamic loading, both experiments and numerical simulations are performed at different impact velocities, respectively. Experiments are carried out with the Split Hopkinson Pressure Bar (SHPB), and numerical simulation is conducted using Holomquist-Johnson-Cook (HJC) model incorporated in the software LS-DYNA. Numerical results are in good agreement with experimental data. According to the normal stress, maximum shear stress and transversal strain distribution, the fracture process is analyzed through simulation. It is found that soft rock materials have at least two failure modes instead of a single failure mode. The fracture mechanism of sandy mudstone is mainly governed by the shear and tension failure.

1 INTRODUCTION

Since the geological conditions of civil engineering are complex, the tunnel is inevitably within soft rock mass. Underground rock engineering is normally excavated using the drilling and blasting method, and thus the rock is subjected to dynamic loading. However, compared with the rock mass under static loading, there are different mechanical performances for rock mass under dynamic loading (Zhang & Zhao 2014). In order to investigate the influence of dynamic loading on tunnel after excavation, the performance of the soft rock mass under dynamic loading needs to be researched, which can provide the theoretical guidance to rapid tunnel support of soft rock mass, post protection as well as rock burst prevention.

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