| As an important coal production base in East China,the Huaibei mining area has caused surface tension cracks along with coal mining activities,posing a great threat to the local ecological environment and engineering construction.This paper takes Suntuan coal mine 1047 face in Huaibei mining area as the research object,through mining data collection,on-site investigation,indoor experiment,field test and numerical simulation,etc.Technology and other research,the main research results are as follows:1.According to on-site investigations,the development of tensile fissures on the surface of 1047 working face in Suntuan Coal Mine is significant.According to their development characteristics,tensile fissures can be divided into two types.Nearly parallel Z fissures in wind lanes and machine lanes.2.By using unmanned aerial vehicle photography,ground penetrating radar,pit exploration and field measurement,the transverse fissures developed on the surface of No.1047 working face in Suntuan Coal Mine are mainly located about 50m in front of the mining position of the working face,showing the development law of fissures from generation to development to closure with the advancement of mining activities.The fissure development width is 2?45mm,the depth is about 5.0m,which is basically parallel to the cutting direction,and the development length and scale are different;The longitudinal fissures nearly parallel to the wind tunnel show the development law from generation to development to stability.The fissures have a width of 8?150mm,a depth of about 6?8m,and a long extension length.They develop at 50-160m around the working face and form an angle of 15 with the direction of the machine tunnel and the wind tunnel.3.Indoor simulation tests have found that changes in water content have a significant impact on the development of tensile fractures.As the water content of the clay body increases.the width and depth of the tension cracks are significantly reduced,and the time for the formation of tension cracks is obviously delayed;when the water content increases to 40%,no tension cracks will occur.The change of the soil surface stress environment has a significant impact on the development of cracks.Tensile cracks preferentially expand at the scratches,which can effectively avoid the occurrence of cracks at the original tensile cracks.4.Field tests and geological radar surveys show that increasing the moisture content of the upper soil on the working surface through humidification technology has a significant effect on inhibiting the development of surface tension cracks;the stress guiding method can change the development direction of surface tension cracks within a certain range.5.From the results of FLAC3D numerical simulation,it can be seen that during underground mining,the tensile stress concentration area in the X direction appears within the range of 100?150m on the two wings of the working face,and the tensile stress concentration area in the Y direction appears 50m directly in front of the mining position of the working face.With the advancement of coal mining activities,the X-direction tensile stress concentration area on the surface extends at an angle of 15°with the excavation boundary,and the stress increases;the location of the Y-direction stress concentration area on the surface follows the advancement of underground mining Moving forward,the previous Y-direction tensile stress concentration area will become smaller.6.According to the numerical simulation analysis,by drilling and increasing the temperature on the surface,the stress guiding method can effectively change the location of the Y-direction tensile stress concentration area on the surface and extend it to the direction of the borehole connection;after humidification,it can effectively reduce Tensile stress in the X direction of the ground surface,and change the location of the X direction tensile stress concentration area. |
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