| With the coal resources in eastern China gradually turned to deep mining,coal mine disaster threat facing more and more serious,and many mine are not face single disaster threats,The Zhaogu No.2 Mine has been affected by long-term disasters such as outburst of gas and floor water inrush.In order to prevent the occurrence of coal and gas accidents,the regional gas treatment method developed by Zhaogu No.2 Mine is the upper layer coal gas drainage through the rock stratum in the construction floor rock tunnel;The Jiaozuo mining area is recognized as the water inrush serious mining area,The Zhaogu No.2 Mine is a typical mine in the Jiaozuo Mining Area,the floor gas drainaging roadway has always faced a severe floor water inrush challenge after digging;At the same time,after the tunnel excavation,the subsidence of the roof,the convergence of the two supports,the instability of the supporting body,etc.,have occurred.The stability of the surrounding rock has also become a constraint in the safety production of the mine.Therefore,under the conditions of deep mine,confined aquifer and mining stress,the safety problem of the floor gas drainaging roadway in the Zhaogu No.2 Mine has become an urgent issue.In this paper,use the floor gas drainaging roadway above the deep confined water as the background,using the field investigation,mine pressure observation and laboratory experiments to analyze the specific issues faced by the floor gas drainaging roadway;Through theoretical analysis and numerical simulation,the failure law of roadway surrounding rock under the influence of horizontal stress-dominated tectonic stress field and under confined confined aquifer is obtained,Studied the "butterfly-type water inrush" mechanism under specific conditions;Using the numerical simulation of the equivalent filling of the falling rock mass in the goaf,the distribution characteristics of the floor stress and the distribution law of the stress ratio and the evolution of the ratio of the bidirectional stress under the influence of the mining are obtained;Based on this,numerical simulation analysis was used to study the distribution characteristics of the plastic zone of the surrounding rock when the floor gas drainaging roadway is at different positions below the working face,and the reasonable location selection of the floor gas drainaging roadway is obtained;Finally,considering the influence of the support resistance on the plastic zone of roadway surrounding rock under the deep conditions,this paper discusses the control ideas and supporting principles of the surrounding rock of the floor gas drainaging roadway in the Zhaogu No2 coalmine,Some issues have proposed several engineering proposals and have achieved the following main conclusions:(1)Under the influence of water pressure,the recessive equation of the plastic boundary of surrounding rock under circular bidirectional non-isostatic stress field is obtained:It can be seen that the main factors influencing the size of the plastic zone of surrounding rock in the underground roadway under deep confining pressure are the surrounding rock factors(cohesive force C,internal friction angle ?,and roadway radius r0)and stress factors(vertical load ?H,biaxial stress ratio ?,and floor water Pressure Pw),while the surrounding rock factor is relatively fixed in the determined geological engineering,is the basis for determining the characteristics of the roadway surrounding rock plastic zone,and the stress factor is subject to a greater degree of fluctuation under the influence of tectonic stress and mining stress.It is the main variable that affects the size of the plastic zone in the roadway surrounding rocks.(2)It can be seen from the RPP total stress ratio curve that under the deep conditions,when the ratio of the biaxial stress increases(?>1)or decreases(?<1),the expansion characteristics of the plastic zone of the surrounding rock are similar,and the plastic zone will appear.The circular?elliptical?butterfly-type transition and the linear growth of plastic zone size?controllable growth?malignant growth trend,so the different regions of RPP curve can be defined as linear slow growth zone,butterfly controllable zone and butterfly shape.Malignant growth area.(3)When ?>1,the ultimate stress ratio of the RPP curve under different water pressure conditions increases with the increase of the applied water pressure.Under the condition that the stress ratio is the same,the greater the water pressure is,the larger the corresponding plastic zone is.The smaller the radius is,so when the horizontal stress is greater than the vertical stress,the water pressure will inhibit the expansion of the plastic zone of the surrounding rock of the bottom extraction tunnel;when ?<1,the limit of the RPP curve under different water pressure conditions The ultimate stress ratio also gradually increases with the increase of the applied water pressure.Under the condition that the stress ratio is the same,the greater the water pressure is,the larger the maximum radius of the plastic zone is,so the horizontal stress is greater than the vertical stress.Under the circumstances,water pressure will promote the expansion of the plastic zone surrounding rock in the underground pumping tunnel.Under the influence of the original rock stress field,the hydraulic pressure is inhibited in the plastic zone expansion of the bottom pumping lane in the area above it;under the influence of the mining of the upper working face,the hydraulic pressure is the expansion of the plastic zone of the surrounding rock of the underground pumping tunnel.Promote effect.(4)In the larger biaxial stress ratio environment,when the surrounding rock failure characteristics of the bottom extraction tunnel presents a "butterfly-type",a small change in the stress ?? will cause a vicious extension of the plastic zone of the roadway surrounding rock,when the plastic failure scope and below When the water-bearing structure(aquifer and confined water lead-up zone)is connected,the floor water will enter the destructive rock body through the plastic failure of the surrounding rock of the underground pumping lane and the conduction point of the water-conducting structure,and finally flow into the production space.,causing a water inrush accident.Therefore,the non-uniform and malignant expansion of the plastic zone will occur only when the plastic zone presents a “butterfly” feature,so that the necessary water-conducting channels for water inrush can be formed.Therefore,this “butterflies” expansion of the surrounding rock of the underground pumping roadway is expanded.The resulting water inrush is called "butterfly-type water inrush",and the necessary condition for the occurrence of " butterfly-type water inrush " is the existence of a large bidirectional stress ratio in the stress field of the surrounding rock.(5)Through the use of Double yield equivalent filling method to deal with the goaf,it solves the problem that the stress in the goaf is not restored and the supporting pressure of the coal pillar is relatively high when the traditional numerical simulation excavation calculation is not performed on the goaf.Disadvantages,at the same time,can better reflect the stress-strain relationship of the broken rock mass under overburden rock in the goaf.By analyzing the distribution law of vertical stress in the numerical simulation scheme,we can find that the simulation results are consistent with the distribution law of the abutment pressure of the coal bed after mining,indicating that the model uses a dual zone service model to simulate the cracked rock mass in the collapse zone,and after the face mining Hysteresis filling simulation scheme rationality.(6)Considering the actual conditions of the site,the longitudinal layout of the bottom-drainage tunnel in the Zhaogu No.2 Mine is considered to be driven along the bottom in the sandy mudstone above the L9 limestone.The central position of the roadway in the bottom-drainage lane is about 13 meters away from the coal seam floor in the direction of the longitudinal layer.The distance of m,and through numerical simulation,it can be seen that within a distance of less than 10 m from the coal seam,the peak value of the ratio of the bi-directional stress and the stable value decrease with the increase of the distance from the bottom plate,and the degree of reduction is obvious.When the distance to the coal seam is greater than 10 After m,the decreasing amplitude of the bi-directional stress ratio peak value and the stable value with the increase of the base plate distance begin to exhibit an approximately linear law,and then the rationality of the selection of the vertical floor selection for the bottom extraction tunnel is verified.(7)Under the influence of mining stress,the change of vertical stress is obvious and the horizontal stress variation is limited.Therefore,the ratio of bi-directional stress shows a drastic change of regularity in the coal wall below the goaf.According to the stress state and biaxial stress ratio characteristics of each area,the area where 1<?<1.3 is less affected by the mining stress can be defined as the area of the original rock stress ratio;the vertical stress is in the pressurized state and 0.53<?<1.The area is the “Pressure Low Stress Ratio Area”;the area where the vertical stress is in the pressure relief state and 1<?<3 is the “Relief Pressure Low Stress Ratio Area”;the area where the vertical stress is in the pressure relief state and ?>3 is “Discharged.Pressure high stress ratio zone".(8)Below the goaf,the bidirectional stress ratio appears to be higher at the edge of the goaf and lower in the middle of the goaf.In the longitudinal direction,the bidirectional stress ratio shows a "high and low peak" shape characterized by a peak at 20 m behind the working face,a low peak at 20 m in front of the opening,and a stable distribution of the stress ratio between the two peaks;The bi-directional stress ratio exhibits a peak point symmetrically distributed at a distance of 20 m from the coal wall and gradually decreases the stable M-type distribution characteristics between the two peaks,and its four peak points are respectively distributed at four right angles of the goaf.According to the stress ratio,the "pressure relief high stress ratio belt" is mainly distributed in the back of the working face 10 m to 50 m,from the coal wall more than 10 m in the goaf area and 10 m to 40 m away from the cut-off eye 10 m to 30 m from the coal wall End symmetrical area.(9)The final failure state of surrounding rock of the underground pumping tunnel under mining influence is determined by the worst stress environment experienced by the surrounding rock under the influence of mining stress.Considering the evolution law of the ratio of the biaxial stress ratio,the bottom drainage tunnel is considered.The ratio of the worst-case ratio of bi-directional stress when located within the projection range of the gob area is: within the projection range of the coal wall,the “supercharged low stress ratio zone” and the “rock stress ratio zone” formed during the last step excavation are adopted.The ratio of the worst bidirectional stress in the projection range of the void region is the peak point of the bidirectional stress ratio generated after the excavation of each step is completed;the distribution rule of the worst ratio of the biaxial stress when the bottom extraction lane is located outside the projection range of the goaf is the working surface.After the final excavation is completed,the "supercharging low stress ratio zone" is formed.(10)Under the effect of mining in a single working face,the surrounding rock is subjected to the “pressure relief high stress ratio” environment when the bottom pumping lanes are arranged in the wrong way,and the floor rock is more likely to be “butterfly”,even if the adjacent working face mining stress is only The slight influence on it will also make the “butterfly” damage scope drastically increase.When the bottom-drainage roadway is arranged outboard,the surrounding rock is affected by the “supercharged low stress ratio” environment,and the surrounding rock of the underground pumping lane is more slowly extended in the plastic zone.The “linear slow-growth” state,so even if the influence of mining stress on the adjacent working face has a great impact on it,there is no malignant increase in the depth of the floor rock surrounding rock in the bottomdrainage roadway.(11)According to the influence degree of drainage tunnel water inrush danger on the bottom of the four stress state sort can be ranked as: pressure relief high stress ratio area> relief pressure low stress ratio area> pressure boosting low stress ratio area> original rock stress ratio area,according to the water inrush risk size of three kinds of layout sorting can be ranked as: internal 25m> internal 80 m> external 15 m.(12)From the consideration of the stress environment of the floor,the gas drainage efficiency,and the prevention and control of water in the working face,the optimal location of the floor gas drainaging roadway of 11060 working face in the Zhaogu No.2 Mine is along the normal direction of the work face to be mined and is located below the central pillar of the planned L9.and in the sandstone mudstone upper part of the limestone excavated along the bottom.(13)Under the condition of deep roadway surrounding rock plastic zone is in a given state,namely the destruction of roadway surrounding rock under deep conditions by the extent of damage of roadway surrounding rock at high stress level of the stress field in decision support,provide supporting resistance due to the original rock stress field far,and can not be changed the vast majority in the state of roadway surrounding rock shear failure,can reduce or eliminate the damage state of roadway surface tension.(14)floor gas drainaging roadway of Zhaogu No.2 Mine's supporting principle is: In the early stage of roadway excavation,support methods are adopted that can take long anchor rods as support cores to achieve support body coordination of surrounding rock deformation and release of the pressure “let” pressure of the roadway.Supporting,after the surrounding rock stress is released to a certain degree,it is necessary to adopt a secondary support method of “resistance” to maintain the stability of surrounding rock. |
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