Research On Anomalously Low Friction Effect Of Block Mass In Surrounding Rocks Of Deep Underground Cavern

The geological environment of deep rock mass is complicated,and it is usually considered as a series of block rock mass in different dimensions.Under dynamic disturbance,deep rock tends to respond differently from the shallow rock mass.Anomalously low friction effect is one of the most important scientific phenomena.In underground engineering,the blasting excavation induced anomalously low friction effect,which caused the equilibrium condition to be damaged.It is easily to cause dangerous rock mass impact disasters and pose a threat to the safety of equipment and personnel.In this paper,the characteristic of the anomalously low friction are studied,and the theoretical model of the surrounding rock mass in the underground sidewall is established.The influence of some factors on the anomalously low friction effect is studied from the theoretical and numerical simulation.Further studies are carried out with consideration with both preliminary and engineering issues.The main contents and conclusions of this paper are as follows.(1)The feasibility of explicit dynamic finite element method in studying the problem of anomalously low friction effect is verified by combining the block experiment.The theoretical model of anomalously low friction of the surrounding rock mass in the underground sidewall is established.The internal mechanism of anomalously low friction effect when the block is subjected to blasting disturbance is analyzed from the point of force characteristics and energy.(2)The numerical model of the surrounding rock mass in the sidewall is established,and dynamic response of the block under blasting disturbance is studied.The existence of anomalously low friction effect is further verified by analyzing the horizontal displacement and normal stress characteristics of the block rock mass.It is revealed that the mechanism of anomalously low friction effect is the redistribution of normal stress and the change of dynamic friction coefficient.(3)The influence of explosion load,horizontal and vertical in-situ stress and block rock mass size is studied.The change rule of horizontal residual displacement,normal stress and deformation characteristics of block rock mass is analyzed when the factors are changed.When the explosive load and horizontal in-situ stress increase,the anomalously low friction effect becomes more obvious,and the horizontal residual displacement of block increases.With the increase of vertical in-situ stress,the anomalously low friction effect is weakened and the horizontal residual displacement decreases gradually.Under the same blasting disturbance,the bigger the block rock mass,the less obvious the anomalously low friction effect.(4)The displacement mutation induced by anomalously low friction effect induced by blasting disturbance is studied.The mechanism of deformation mutation is studied by establishing the numerical model of cutting excavation and two block.At the same time,by analyzing the simulation results of two block rock mass model,it is found that the outer block residual displacement is larger than that of the inner block,but it is smaller than the single block rock mass.It shows that the number of blocks has an influence on the anomalously low friction effect.