Numerical Simulation Research on the Stress Response of the Bent Rockbolt with the Shear Displacement of Rock Mass

More and more attentions have been paid to the problem of the shear failure in the conventional straight rockbolt support for underground excavations. Different bolting innovations have been tried over the years. The bent rockbolt with promise is a new mean of rock support. Through numerical simulation software, the shear characteristics of the bent rockbolt is analyzed. Three-dimensional numerical models of the bent rockbolt and the straight rockbolt are established. both of which are subjected to a shear displacement of rock mass. Their stress and deformation characteristics results show that stress concentration easily occurs at the intersection point of anchored portion and non-anchored portion along the bolt. In the case of the mises equivalent stress, the bent rockbolt has a smaller one than the straight rockbolt under the same shear displacement of rock mass. So the bent rockbolt is not easy to be damaged and can better adapte to the shear damage of rock mass. Introduction It is widely accepted that joints in rock mass can affect the safety and stability of underground excavations including mining, tunneling, and other type of engineered caverns[1]. The rockbolt plays a key role in the mechanical properties, deformation characteristics and instability modes of rock mass support[2]. For instance, the shear test showed that the anchored surrounding rock mass obviously had tensile, shear and compression zone along the tunnel radius[3]. According to the rock-like simulation test, the shear deformation occurred in the middle of the rockbolt due to interlayer shear dislocation in the roof of deep surrounding rock[4]. In addition, in the investigation of hard brittle rock mass support, it was found that the failure of anchored rock mass was caused by the combined action of tensile and shear force. When the bolt had a small transverse deformation, The bolt would snap before it achieved the best support effect in the axial deformation[5], shown in fig.1(a).The maximum horizontal stress theory partly explained the shear failure of bolt[6]. Under the maximum horizontal stress, the roof and floor of the tunnel easily suffered shear load, the rockbolt is used to control the shear movement of rock mass in the direction perpendicular to the axialdirection, shown in fig. 1(b). (a) (b) Figure 1. Shear failure of the straight rockbolt in rock mass and its reason[5,6] Ludvig believed that the reinforcement capacity of the rockbolt is determined by its maximum radial deformation capacity and shear strength, the former depends on the direction of the rockbolt relative to the shear plane, and the latter depends on the strength parameters of the rockbolt[7]. Bjurstrom has systematically studied the shear behavior of granite under full-length anchorage. It is The straight rockbolt Shear International Conference on Modeling, Analysis, Simulation Technologies and Applications (MASTA 2019) Copyright © 2019, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Advances in Intelligent Systems Research, volume 168