Study On Ultra-low Friction Effect Of Whipping Structure Of Block Rock Mass

With the continuous increase of mining depth,rockburst and rock burst caused by ultra-low friction effect become more frequent and serious,the stress environment of rock mass becomes more complex,and its mechanical behavior gradually presents new forms and characteristics.The in-situ observation of rock burst shows that the existing studies have not fully considered the fracture characteristics of deep rock mass structure,and there are many inapplicable situations.As a result,some special dynamic response phenomena cannot be reasonably explained.To further promote efficient,safe,and environmentally friendly mining of mine resources in China,it is urgent to establish a new research model based on existing research and fully consider the characteristics of structural fracture.This paper introduces the special structure of rock mass in the process of mining.This special structure is composed of many broken massive rock masses,which is particularly similar to the structural characteristics of the"whipping effect".Therefore,this special structure is collectively referred to as the"whipping structure"below.For coal mining process often encounter problems of rock burst and impact ground pressure and other projects,fully consider the more deep,more broken coal and rock characteristics,lash based on rock mass structure to carry out further research work,the building block is respectively to intermediated-acidic lash structure of ultra-low friction effect research model,the structure of the lash coal and rock block system of ultra-low friction effect research model,It is studied utilizing experiment and numerical simulation.Firstly,the ultra-low friction effect dynamic response mechanism of block rock beam structure under the combined effects of external loads such as stress wave disturbance,horizontal shock,and axial compression is studied by using the self-developed ultra-low friction effect test device.The influence laws of stress wave disturbance,impact strength,size,location,height-width ratio,and other factors on the ultra-low friction effect are analyzed.Secondly,based on the experimental study on the ultra-low friction effect of the block rock structure,the ultra-low friction effect of the block coal rock structure is studied,and the similarities and differences of the response mechanisms of the ultra-low friction effect of the two types of block rock structure are pointed out by the comparison between them,which provides a reference for guiding the field.Finally,based on the preliminary test results,FLAC-3D was used to explore the influence of the size and position of the working block on the ultra-low friction effect strength of the block rock structure and the ratio of the height to width of the working block on the ultra-low friction effect strength of the block coal rock structure under different working conditions.In summary,the important conclusions are as follows:(1)Combined with the nature of rock mass"the deeper,the more broken"and the structural characteristics of the whipping effect,a simplified research model of the whipping structure existing in rock mass was established,and the whipping effect of rock mass was proposed for the first time.The influence mechanism of the main influencing factors,such as size,position,and height-width ratio,on the ultra-low friction effect strength of the rock mass whipping structure,was analyzed.It was found that the horizontal displacement duration curve of the working block mainly had a stable stage,sudden increase stage,and second stable stage.The displacement value of the second stable stage was used to represent the ultra-low friction effect strength of the working block.(2)different disturbance intensity of stress wave propagation in the medium is not completely consistent,through the analysis of stress wave disturbance under the action of block system to intermediated-acidic lash structure and block system work lash structure in coal and rock block horizontal displacement response under four location conditions can be found working block horizontal displacement along with the increase of its location(2-5)appear to reduce the increasing trend,The p-4 condition is a critical position and the structure stability at this position is good,which can effectively reduce the influence of ultra-low friction effect of rock mass whip structure.(3)For the studied working conditions,it is found that the stress wave disturbance intensity has no significant influence on the working block with different sizes(S_w=40-100mm),but when the working block is coal,the stress wave disturbance frequency has a significant influence on its horizontal displacement in the size region(S_w=40-70mm).Quality of piece of ultra-low friction effect in rock mass lash structure is nonlinear,the influence of the dynamic response with the increase of the quality is not present a single change,at the same time shows that different quality block under different disturbance generated by the dynamic response of different levels,the response depends to a great extent,the disturbance frequency stress wave and block its natural frequency,Based on the significant influence area of quality given in this paper(sandstone:0.2-0.4kg,coal:0.3-0.7kg),it provides a basis for effectively avoiding the resonance between mechanical disturbance and broken rock mass in engineering.(4)The ultra-low friction effect of the whipping structure of block rock mass shows two characteristics of fluctuation and stability under the action of different stress waves.Due to the different physical and mechanical properties of different rock masses,the horizontal displacement response of the working block is different.There are obvious fluctuation zone(H_w/S_w=0.4-1.2)and stable zone(H_w/S_w=1.2-2.0)under different stress wave intensity.However,the structure of block coal and rock is relatively stable under different stress wave disturbance intensities,but the dynamic response induced by some conditions is very obvious.(5)Based on the preliminary experimental research,the ultra-low friction effect of the whip structure of block rock mass was studied under different working conditions by numerical simulation.Based on the simulation study of rock tip structure,it is found that the dynamic response is most intense when S_w=40mm.Location:P-4 is the most dangerous;Based on the simulation study of coal and rock spur structure,it is found that h-80mm has a strong dynamic response in terms of height ratio.Width ratio:w-80mm is relatively dangerous.Due to the difference between external load and application process used in test and simulation,the law obtained between them is not the same,which can provide some reference value.There are 77 figures,15 tables,and 72 references in this paper.