In order to reveal the dynamic load transfer characteristics and strong ground pressure mechanism when passing through parallel coal pillars in shallow close-distance coal seams mining,field measurement,physical simulation and theoretical analysis were performed to study the movement and load transfer characteristics of the"coal pillar inverted trapezoidal"structure with the lower interval rock strata by taking the 43207 working face of Yujialiang Coal Mine as the engineering background.The transfor law of front abutment pressure and support load is obtained,and the coupling structural mechanics model of"coal pillar-interval step voussoir beam"is established.The calculation formula of support working resistance at the moment of strong ground pressure and after roof cutting were proposed.The results show that the concentrated stress and transfer load of the inverted trapezoidal overburden of coal pillar are mainly concentrated in the rear section of coal pillar,and the load in this area is the main cause of the strong ground pressure of working face when passing through the overlying coal pillar.At the early stage of working face entering the coal pillar,the stress of coal pillar is bimodal;when the working face is to pass coal pillar boundary,the stress concentration distribution is single-peaked,which is located in the back section of the coal pillar.When the working face is 4 m away from coal pillar,the front abutment pressure in the back area of coal pillar reaches the peak value of 6.00,and cracks appear in the interval strata.When the coal pillar is 5 m away from coal pillar,strong ground pressure occurs,and the stress of coal pillar decreases by 43%.During the period of strong ground pressure,the stress of coal pillar is transmitted to the overlying rock layer of 7 m above coal pillar(the middle of the key stratum of the interval strata),which is reduced by 39%,indicating that the roof structure bears a considerable load.Based on the theoretical calculation of the step voussoir beam structure of the interval strata,the calculation formula of the support load at the moment of strong ground pressure is obtained.According to the average stress of coal pillar,the support load is calculated to be 22.9 MN/frame.According to the stress of the rear section of coal pillar at the time of strong ground pressure,the support load is calculated to be 24.1 MN/frame.The load transmitted from coal pillar to the support is only 12%-18%of the total load of coal pillar,which still exceeds the rated working resistance of field support by 9.2 MN/frame.Therefore,to prevent support crushing,the rated working resistance of support needs to reach 15 MN/frame,or the coal pillar and the interval strata structure are treated to ensure safe mining.
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