EXPERIMENTAL AND NUMERICAL ANALYSIS ON THE ARCHING ACTION FROM STRESS ADJUSTING IN SURROUNDING ROCKS

In this paper,after the stress analysis of surrounding rocks,excavation simulated experiments and numerical calculation are applied to study the characteristics of arching action under conditions of different rock properties.Firstly,inner boundary and thickness are used to define an arch in surrounding rocks and to evaluate the stability of underground openings.When the inner boundary is near openings,the surrounding rocks are stable.The thickness of arching action indicates the extent to which the surrounding rocks are influenced by excavation.Less thickness means fewer rocks are used to sustain their own weight and that of rocks above.Then,the arching action is defined in the excavation simulated experiment.In this experiment,it is observed and analyzed that the increase of tangential stresses occurs and an arch is formed around an opening.Data from the experiment show that the increase of displacements is greater near the opening.In numerical analysis,it is found that joints have great influence on the formation of an arch.The position of inner boundary of pressure arch is far away from an opening and thickness is greater with the decrease of joint space.And,in rock mass containing two sets of joint,when a joint incline angle is 30 degree or 60 degree respectively,it is disadvantageous for an arch formation.In addition,the influence degree of joint cohesion on arching action is related to joint friction angle.When the joint friction angle is more than 20 degree,the joint cohesion influence is negligible.