Study On In-situ Stress Characteristics And Its Control Mechanism On Mining Failure Of Floor In Baode Coal Mine,shendong Mining Area

With the continuous expansion of the mining scope and the gradual increase of the mining depth in Shendong mining area,many phenomena and problems different from the characteristics of shallow mining have appeared in the mine,which makes the monitoring and management of mine pressure,water damage,gas and coal seam spontaneous combustion face new challenges,and puts forward new topics for the prediction and prevention of mine disasters.According to the geological environment characteristics of mining areas in Western China,and based on the occurrence conditions and mining characteristics of coal seams in Shendong mining area,strengthening the research on the characteristics of in-situ stress and its control mechanism on the mining failure of coal seam floor is of great significance to the safe and efficient mining of coal resources in Western China.Taking Baode coal mine in Shendong mining area in Western China as the research object,this paper systematically studies the characteristics and distribution law of in-situ stress in Baode coal mine by using multi-disciplinary theories such as structural geology,engineering geology,rock mass mechanics,material mechanics and mining,and comprehensively uses theoretical analysis,physical simulation,numerical simulation,field detection and other research methods to reveal its control mechanism of mining floor damage.The main achievements of this paper are as follows:（1）The characteristics of paleotectonic stress field in Baode area are systematically analyzed:the Indosinian tectonic stress field is mainly in the near SN direction,and the Indosinian structure is very weak in the study area;In Yanshanian tectonic stress field,NW-SE direction is the main compression direction;In Himalayan period,the direction of tectonic stress field changed greatly,and the compression direction changed to NE-SW direction.The structural system characteristics of the mining area in different geological periods laid the deformation foundation for the current geological structure pattern,and played a certain role in controlling the development of basement structure in the mining area.（2）Based on the Kaiser effect of rock,the in-situ stress of Baode mine is measured by acoustic emission technology,and the distribution characteristics and laws of in-situ stress field are analyzed:（1）Vertical principal stress is 11.77～13.38 MPa,the maximum horizontal stress is 16.45～19.34 MPa,and minimum horizontal stress is 9.66～12.08 MPa.（2）With the increasing buried depth,the vertical principal stress increases linearly and the maximum horizontal principal stress and minimum horizontal principal stress generally shows an increasing trend,but the dispersion is obvious.The variation relationship of internal pressure coefficients K₁,K₂,K₃ and K₄ in different buried depth gradient ranges is more complex.（3）Based on the variation characteristics of in-situ stress in different depth gradients,the elevation of500 m can be used as the boundary of deep and shallow division of Baode mine.（4）Combined with the collected in-situ stress data,the differences of in-situ stress distribution between Shendong mining area and Huainan mining area,Panxie Mining Area and Yanzhou Mining Area in Shandong Province are analyzed.（3）The initial in-situ stress field in the mining area is inversed based on multiple linear regression method.The results show that:（1）The inversion effect is good,and the highest accuracy is99.77%.（2）There are great differences in the spatial distribution of stress in XX,YY and ZZ directions within the mine field.（3）The in-situ stress is greatly affected by the river,elevation and other factors in the shallow part of the surface.With the increase of buried depth,the control effect of landform on the stress in all directions gradually weakens.（4）The physical model and numerical model considering in-situ stress field and its influence on mining failure of floor are constructed,and the displacement,stress and plastic failure characteristics of the mining floor are systematically analyzed.The results show that:（1）The floor cracks develop continuously with the advance of the working face,and the failure depth increases continuously.The deepest crack can reach 7 cm,the width is 10 cm,and the angle with the horizontal direction is 30°～70°;（2）The coal seam roof has a large periodic collapse every 10～15 cm,and the floor has a large fracture every 20～22 cm.The periodic deformation and failure of the floor is consistent with the periodic pressure of the roof.（3）The stress monitoring results show that the stress variation characteristics of each monitoring point are consistent as a whole,and the stress state of the floor in front of the coal seam is compressed first.（4）The numerical analysis results show that under the condition of horizontal tectonic stress field,with the excavation of working face,the stress of top and bottom plate,the failure of plastic zone and the vertical displacement of surrounding rock change and adjust continuously.The maximum stress in front of working face is 25.55MPa,and the maximum failure depth of bottom plate is stable at 30 m.（5）The mechanical model of mining failure of coal seam floor is constructed,the stress characteristics under the action of supporting pressure under the semi infinite plane are analyzed,the analytical solution of mining rock mass stress of coal seam floor is solved,and the variation laws of horizontal stress,shear stress,maximum principal stress and minimum principal stress of floor rock mass are obtained by using Matlab software,so as to reveal the stress distribution state of floor rock mass.（6）The numerical calculation model of mining floor failure under in-situ stress is constructed,and three different lateral pressure coefficients are discussed（λ=0.5、λ=1.0、λ=1.5）stress distribution,deformation and failure characteristics and evolution law of floor rock stratum under conditions:（1）the lateral pressure coefficient has a great impact on the mining stress distribution of roof and floor rock stratum,which directly affects the stability of roof and floor rock stratum.（2）With the increase of the lateral pressure coefficient,the range of the surrounding rock plastic zone of the roof and floor of the working face gradually increases,and the expanded range of the floor is significantly larger than that of the roof.（3）The vertical displacement height of the bottom plate shows an increasing trend with the increase of the lateral pressure coefficient,which makes the bottom plate easy to bulge and cause damage;However,the vertical displacement of roof rock stratum decreases continuously,which is easy to form structural balance and maintain stability.（7）The comprehensive detection of roadway and working face floor in 81307 working face of Baode coal mine shows that:（1）The GPR detection of roadway floor has found 5 anomalies in the radar section,and the development depth of fracture zone is generally in the range of 10～20 m;（2）The three field monitoring of stress field,fracture field and seepage field shows that the influence range of advance mining stress in working face is 80～120 m,the influence depth is about 25 m,and the mining failure depth of floor is about 20～25 m.the formation process of mining failure fracture is basically consistent with the evolution law of mining stress;（3）The damage depth of the bottom plate obtained by the combined well hole microseismic monitoring is 30 m.（4）Based on the geological radar technology and multi field coupling monitoring technology,the detection results are basically consistent with the numerical calculation and microseismic monitoring results.The failure depth of the floor is less than 30 m.Figure[112]Table[23]Reference[214]...