Experimental Research On Shear Creep And Fatigue Energy Evolution Of Deeply Anchored Jointed Rock Mass

With the continuous development of society and economy in recent years,many underground projects have been carried out in the Midwest of China.The complexity of the environment in which the deep underground works are located often leads to the existing research results of rock mass anchoring mechanism which can not accurately reflect the actual anchoring situation of rock mass.Therefore,it is of theoretical and practical significance to explore the mechanical characteristics and internal energy evolution mechanism of deep anchored joint rock mass under complex stress conditions.In order to explore the mechanical characteristics and internal energy evolution mechanism in the process of deformation and failure of anchorage joint rock mass,this paper takes anchorage joint rock as the research object to carry out the graded shear creep fatigue test based on the full summary of previous studies.Based on the indoor test,theoretical analysis and numerical simulation,the shear creep fatigue mechanical characteristics of anchorage joint rock mass are analyzed.The following results are obtained by the energy evolution law and the mesoscopic characteristics:(1)Through indoor shear creep and fatigue test found that compared with no anchor joint shear creep and fatigue resistance of rock mass and anchor joint shear creep and fatigue resistance of the rock mass have greatly ascend,anchorage stress at the time of joint rock mass damage threshold increases with the increase of loading rate,first after the change trend of decrease,damage threshold and stress at the time of loading rate is nonlinear relationship;The stress threshold decreases with the increase of loading frequency,and there is a negative correlation between the stress threshold and loading frequency.The stress threshold increases with the increase of bolt diameter.The increase of bolt diameter is beneficial to the improvement of shear crepage-fatigue resistance of the rock mass.(2)Based on the laboratory test data for anchoring joint energy in the process of damage evolution of rock mass characteristics were analyzed,and the strain energy of the main peak before stage input in the form of elastic energy stored in the anchorage joint rock,joint rock damage after most of the input before stored elastic strain energy and peak into dissipation can quickly,It is used for friction and coalescing of cracks in rock mass and plastic deformation of anchor bolt.With the increase of loading rate,each energy increases first and then decreases,and the relationship between each energy and loading rate is nonlinear.Each energy decreases with the increase of loading frequency,and there is a negative correlation between each energy and loading frequency.(3)The damage of the anchorage jointed rock mass is quantified by the dissipation ratio,and the deterioration of the anchorage jointed rock mass is considered by the loading rate and loading frequency.According to the principle of strain equivalence,the damage equation of the anchorage jointed rock mass is obtained,which is verified by the comparison between the experimental curve and the theoretical curve,and the overall agreement is good.(4)The failure mechanism of anchorage structure and the evolution of the failure mesoscopic characteristics of anchorage joints under different loading conditions and different diameter of anchor are studied by PFC^2Dsoftware.The energy evolution law and the evolution and propagation process of micro crack in the process of shear creep fatigue of anchorage joint rock are analyzed in depth,so as to reveal the energy evolution mechanism and meso shear failure characteristics of the main structure surface of anchorage.There are 61 pictures,16 tables and 85 references.