Analysis of bolt support stress field and bolt support effect under in-situ stress field

In order to clarify the distribution characteristics of rock bolt support stress field and its support effect under in-situ stress field,six kinds of bolt supporting schemes were simulated and analyzed by UDEC-Trigon numerical simulation. The study shows that a reasonable method for obtaining the stress field of bolt support under the condition of in-situ stress and joint factors is proposed. The bolt support stress field distribution is closely related to the pretension force and support density. However,the pretension has a greater influence on the support stress field. The stress field of bolt support shows a sporadic and discontinuous distribution when the pretension is low,and a continuous and overall distribution when the pretension is high. The stress field of bolt support and the strong deformation and failure zone of surrounding rock of roadway shows a game mechanism,i.e.,"big stress field vs small failure zone,and small stress field vs big failure zone". The active restraining force provided by the high pretension bolt not only limits the opening of joint,but also increases the shear resistance of joint,avoids the slippage of joint,and has a significant effect of controlling cracking. The stress field of bolt support consists of two parts:the pretension field of the bolt and bolt sup-port suppress the stress that should be released when the surrounding rock of the roadway is deformed and damaged.The former is the reinforcement effect of bolt support on the surrounding rock without deformation,and the latter is the result of the active and passive restraint control of the deformation of the surrounding rock by bolt support. Although the pretension stress field only accounts for a small part of the stress field of the bolt support,the active restraining force provided by the pretension of the bolt has a great effect on the generation and distribution of the stress field of bolt support.