Study On Dynamic Characteristics And Damage Mechanism Of Coal And Rock Under Coupling Action Of Dynamic And Static Load And Temperature

With the increase of coal mining depth and the increase of in-situ stress and temperature,the influence of dynamic load is more and more significant.The risk of rock burst in the process of deep coal resource mining is becoming more and more serious.Its occurrence and evolution process is closely related to the dynamic properties and failure process of coal and rock mass.At present,there is a lack of in-depth research on the impact failure dynamic characteristics of coal and rock mass under the coupling of dynamic and static load and temperature,and the impact dynamic characteristics and damage failure mechanism of coal and rock mass under the coupling of dynamic and static load and temperature are unclear.In this paper,the dynamic response characteristics of coal and rock under the coupling action of dynamic and static load and temperature are studied by means of laboratory experiment,theoretical analysis and numerical simulation,the temporal and spatial distribution characteristics of stress field and displacement field of coal and rock are analyzed,the impact dynamic constitutive model of coal and rock under the coupling action of dynamic and static load and temperature is established,and the impact instability damage mechanism of coal and rock under the coupling action of dynamic and static load and temperature is revealed.The main conclusions are as follows:The Hopkinson compression bar experimental system for the coupling effect of temperature and dynamic and static load is established,and the impact dynamics experiment of coal and rock at room temperature～100~oC is carried out.The stress and strain laws of coal and rock at different temperatures,axial static load,dynamic load strength and temperature action time and the energy dissipation characteristics of coal and rock at different temperatures are revealed.The results show that temperature,axial static load and dynamic load strength are positively correlated with the dynamic peak stress of fine sandstone;The temperature action time is negatively correlated with the dynamic peak stress of fine sandstone.There is a positive correlation between the peak value of dynamic load and the dynamic load of coal;Temperature and temperature action time are negatively correlated with the dynamic peak stress of coal samples.In the process of coal rock impact failure,the incident energy,reflection energy,transmission energy and dissipation energy first rise to a stable value and then remain relatively stable with the action time of dynamic load;With the increase of temperature,the stable peaks of incident energy,reflected energy and dissipated energy of fine sandstone decrease first and then increase;The incident energy,reflected energy and dissipated energy of coal sample show the law of first decreasing,then increasing and then decreasing.Based on the approximate model method,an approximate model of dynamic stress response of coal and rock under multi factor conditions is established,The effects of single factors(temperature,axial static load,dynamic load intensity,temperature action time)and coupling factors(temperature and axial static load,temperature and dynamic load intensity,temperature and temperature action time,axial static load and dynamic load intensity,axial static load and temperature action time,dynamic load intensity and temperature action time)on the dynamic peak stress of coal and rock are studied.At room temperature～100~oC,the influencing factors of dynamic peak stress of fine sandstone are dynamic load strength,dynamic load strength coupling factor,axial static load,temperature action time and temperature from large to small;The influencing factors of dynamic peak stress of coal samples are dynamic load intensity,axial static load,axial static load coupling factor,temperature and temperature action time from large to small.Using digital image analysis and numerical simulation methods,the temporal and spatial distribution characteristics of stress field and displacement field of coal and rock under temperature,dynamic and static load are studied,and the propagation velocity of horizontal and vertical cracks on the sample surface is calculated.The surface strain of fine sandstone and coal samples increases with the increase of dynamic load stress.There is a phenomenon of strain zoning in the propagation direction of stress wave,and the surface displacement acceleration is distributed in a band.On the time scale,the end face stress and internal stress of coal and rock samples characterize the stress oscillation,showing a multi peak phenomenon;On the spatial scale,high stress appears in the center and edge of fine sandstone,and the stress in the center area of coal sample is higher than that in the edge area.The displacement of elements at different positions of coal and rock samples intersect in time and space,resulting in dislocations.The propagation speed of horizontal crack on the surface of fine sandstone is between 42.10～88.16m/s,and that of coal sample is between 11.13～87.87m/s.The micro morphology characteristics and mineral composition characteristics of coal and rock fracture under the coupling action of dynamic and static load and temperature are studied,the micro mechanism of coal and rock damage and fracture under the coupling action of dynamic and static load and temperature is revealed,the crack group propagation model of coal and rock damage process is established,and the judgment criterion of dynamic stress intensity factor of coal and rock damage under temperature and dynamic and static load is obtained.The impact failure of coal and rock is brittle failure,the fine sandstone is X-shaped conjugate shear failure,and there are obvious cleavage steps and cleavage planes on the fracture surface;The coal sample is damaged in layers,and the fracture is mainly fluvial.Based on the theory of damage mechanics,the damage constitutive model of coal and rock mass under the coupling action of dynamic and static load and temperature is established,and the model parameters are determined.Based on the geological conditions and stope structure of 2233 working face in a mine,the effects of temperature on parameters such as coal and rock mechanics,stress wave velocity and coal rock impact tendency index are experimentally studied.By establishing the stope numerical simulation model of working face under normal temperature and temperature range(33～43~oC),the distribution characteristics of stress and plastic zone of working face before rock burst are determined.The results show that the density and stress wave velocity of coal and rock samples decrease in varying degrees with the increase of temperature;The impact tendency index value of coal samples decreased;In the numerical simulation analysis,the maximum vertical stress concentration factor of the working face increases and the influence range of the plastic region of the working face expands.The research results of this thesis have important theoretical significance and practical value for further revealing the dynamic damage mechanism of coal and rock mass under the coupling action of dynamic and static load and temperature,and promoting the development of rock burst disaster prevention technology.This thesis has 109 figures,23 tables and 191 references.