Study On Surrounding Rock Damage Caused By Unloading Effect Of Roadway Blasting Excavation Under High Ground Stress

At present,the problem of roadway instability caused by the unloading effect of deep rock blasting excavation is prominent.Research on the surrounding rock damage problem of roadway blasting excavation under high ground stress is of great significance to the control of blasting and the safety and stability of underground engineering structures.First,theoretically analyze the ground stress unloading mechanics model at the boundary of blasting excavation.According to the general solution of displacement theory,the influencing factors of the roadway surrounding rock damage are clarified,and the reliability of the dynamic relaxation method and the dynamic solution simulation method are determined by comparing the engineering measurement results.Then,numerical simulation method is used to study the influence law of influencing factors on roadway surrounding rock damage.The main research contents and results are as follows:(1)Analysis of the distribution characteristics of the stress field of the high in-situ stress rock mass and the influence factors of the surrounding rock damage.From the perspective of elasticity,the mechanical model of in-situ stress unloading at the boundary of blasting excavation under high ground stress is analyzed,and the main influencing factors of roadway surrounding rock damage are summarized according to the general solution of displacement theory,namely,load type,roadway shape,initial ground stress,lateral pressure coefficient,The method of unloading and the time of unloading verify the reliability of the simulation method through the engineering test results.(2)Research on the damage law of roadway surrounding rock by load type.The coupling process of the blasting load and the unloading of the ground stress is analyzed.The dynamic relaxation method and the dynamic display simulation method are used to study the influence of the load type on the roadway surrounding rock damage.The study found that: compared with the blasting load and the unloading of the ground stress,the surrounding rock damage in the vicinity of the roadway wall under the coupling effect is mainly caused by the tension and compression of the explosion stress wave and the unloading of the ground stress.The straight edges of the roadway are prone to appear.For fracturing failure,tensile failure is likely to occur at the bottom corners,and the coupling damage to surrounding rock is greater than the superimposition of blasting load and ground stress unloading.(3)Research on the influence law of roadway shape,in-situ stress and lateral pressure coefficient on roadway surrounding rock damage under coupling action.The results show that the stress distribution of the circular roadway is uniform,and the surrounding rock damage is small.The rectangular and straight-wall arched roadways have sharp corners in the excavation,and the formation of stress concentration at the sharp corners causes serious damage to the surrounding rock.In the process of the insitu stress changing from 10 to 40 MPa,the damage range first decreases and then increases.In the lowering stage,the unloading effect is small,and the clamping effect is large,which can restrain the damage of the surrounding rock of the roadway;The unloading effect is greater than that of clamping,which promotes damage to the surrounding rock of the roadway.When the lateral pressure coefficient is not 1,the stress field and damage field of the surrounding rock of the roadway have obvious directionality.The stress field mainly develops in the direction of greater in-situ stress,and the damage field develops in the direction of less in-situ stress.(4)Research on the damage law of the roadway surrounding rock caused by the ground stress unloading method and unloading time.The study found that exponential function unloading has the largest damage range of surrounding rock in unloading methods,followed by trigonometric function unloading,and linear function unloading is the smallest;the shorter the unloading time,the stronger the unloading effect and the damage range of roadway surrounding rock.Bigger.The unloading rate is the main reason affecting the damage of surrounding rock.