Safety Evaluation Of 1026 Working Face DF68 Without Coal Pillars In Wugou Coal Mine

In China,the coal seam threatened by floor limestone water has a wide range of mining points,among which the water inrush and well flooding accidents caused by faults are frequent.The Wugou coal mine studied in the thesis has a very high fault density and a large amount of fault-proof coal pillars left,resulting in serious resource loss.Therefore,how to use modern geotechnical grouting reinforcement technology to transform the fault fracture zone from a water-conducting channel into a water-retaining channel,and realize the fault-free coal-pillar mining,has become the focus of research in geotechnical engineering.Therefore,it is necessary to carry out safety evaluation research on DF68 fault without coal pillar in 1026 working face.Based on the engineering background of reducing the DF68 fault water-proof coal pillars in Wugou Coal Mine to achieve pillar-free mining,on the basis of reviewing the frontier technology and the latest research results of the domestic and foreign water-breaking coal pillars,combined with the ground,underground drilling and physical exploration data,the mining technical conditions of 1026 working face and the water-rich characteristics of DF68 fault are systematically analyzed;The downhole fault exploration,grouting treatment and verification holes were designed and constructed.Rock samples from the fault zone and surrounding areas were taken to test the hydrological and mechanical properties,and the mining evolution characteristic model was constructed.using FLAC^3Dnumerical simulation and other technical means,the failure characteristics of mining roof and floor and fault activation disaster law were analyzed when different fault protective coal pillars were left;Grouting has transformed the fault fracture zone and changed the water barrier property of the fault fracture zone.The Taiash aquifer has been strengthened,and the thickness of the floor waterproof layer has been effectively increased.The grouting effect of fault fracture zone and limestone aquifer has been verified by drilling.The following research results are obtained:（1）The original designed open-cut length of 1026 working face is 62～210m,and the cut is 92～240m after the coal pillar free mining;working face roof elevation is-460.00～-310.0m,coal thickness is 2.12～5.55m,the average coal thickness is 4m,the average dip is 8°,threatened by various water hazards,and the minimum“four containing”coal and rock pillar is 62.4m;the DF68 fault is a normal fault with an extension of 0.83km and a drop of 0～35m.It is located in the south wing of the 1026 working face.Nearby,the fault drop has the characteristics of being large in the middle and small at the two ends.The original 30m fault water-proof pillar was left,and more than 300,000 tons of coal was pressed.The mining of the working face is mainly threatened by the roof"four-containing"water,the floor limestone water and the fault water.（2）The coal seam occurrence and hydrogeological conditions of 1026 working face were systematically analyzed,combined with ground 3D seismic,ground geophysical prospecting,drilling data,and the geological and hydrological characteristics of the DF68fault were appraised,and 8 times of underground transient electromagnetic probe were carried out in the newly designed engine lane,and six geophysical anomaly areas in the fault zone and working face were obtained.（3）Aiming at the abnormal geophysical prospecting area,3 drilling sites were designed in the working face wind and machine lanes,14 drilling holes were drilled in the construction abnormal area and fault exploration.The engineering volume was 743m,and none of the holes produced water,indicating that the DF68 fault is a water-free fault.（4）Use the RMT-150 rigid press,SEM,XRD and XRF and other instruments,the compressive strength and tensile strength of the drilled fault zone and the core of roof and floor were analyzed,obtained the performance parameters of the rock mechanics,rock formations electron microscope scan,X-ray diffraction images,X-ray fluorescence images and particle ingredients SQX calculation data,particle spectrum peak recognition results and micro composition proportion.（5）With the help of FLAC^3Dsoftware,under the condition of keeping different fault protection pillar widths,the plastic zone and the stress evolution law near the fault zone during the mining process of the working face are simulated.In view of the possibility of fault fracture zone caused by coal pillar free mining and floor limestone aquifer,the grouting reinforcement was carried out to partition,with a grouting volume of 6384.4m³.The grouting effect verified that the borehole water output was all less than 1m³/h,indicating that the fault zone grouting changed the property of fault fracture zone,and the water channel of variable conductivity was an impermeable layer.（6）The thickness of the"fourth aquifer"on the 1026 working face is 20.1～26.0m,with an average of 22.33m.According to the water pumping data of the 1026-1 pre-mining hydrological inspection hole in the working face,q=0.00683L/（s.m）,k=0.024m/d,it belongs to a weak aquifer,the water body mining grade is Class II water body,the overburden type is medium-hard type,according to the maximum mining height of 4.8m,comprehensive specifications,measured data engineering analogy,the designed reserved height of safe coal（rock）column for sand control is 36.91m,which is smaller than the actual reserved height of 62.4m,and meets the requirements of the"three under"mining specifications.（7）Coal seam floor elevation of working face is-352.3～-495.45m,limestone water level elevation of Taiyuan Group is-156.24m,water barrier thickness is 42.19～60.55m,with an average of 49.47m.After floor grouting reconstruction,the water inrush coefficient is 0.046～0.059MPa/m,less than the critical value of 0.06MPa/m,which meets the requirements of"Coal Mine Water Prevention and Control Rules".（8）From the perspective of water safety prevention and control,under the premise of monitoring,monitoring,drainage and emergency response plan and other regulatory measures during the mining process,the DF68 fault at the 1026 working face has the conditions for safe mining without coal pillars.When the paper is completed,520m of coal has been safely recovered at 1026working face without any fault coal pillar,and the water inflow from the working face is about 3～5m³/h,which indicates that the methods,means and measures adopted by the research and the conclusions drawn in this paper have high credibility and generalization.Figure[82]table[21]reference[73]...