Research on support resistance of contiguous coal seam mining under room-and-pillar gob

In order to study the reasonable support resistance of contiguous coal seam mining under room-and-pillar gob,based on the actual geological conditions of Shigetai Coal Mine,the mechanical models of primary and periodic breakage of key layers under room-and-pillar gob were constructed to obtain the initial and periodic weighting intervals,and the corresponding “support-rock” interaction mechanical models were constructed to calculate the working resistance of the support.The results of the study indicate that there are two main features of the key strata breaking step under room-and-pillar gob mining:① The first breaking and periodic breaking step of the key layer are closely related to the stress concentration degree of the coal pillars left above; ② The breaking step size is greatly affected by the location of the key layer’s previous break.The initial striking step of the key stratum of the No.31201 fully-mechanized coal mining face is 40.1 m by theoretical calculation,and the striking step of the first three cycles is 20.4 m,18.9 m,and 20.8 m.Compared with the uniform load condition,there are two main influencing factors for the determination of the support resistance under room-and-pillar gob mining:The position where the key layer is concentrated by the overlying rock layer;The structural form of the first break of the key layer.Theoretical calculations show that the reasonable working resistances during the first weighting and the first three periodic weighting are 17 372 kN,11 722 kN,15 252 kN and 15 206 kN.The rationality of the theoretical derivation is verified by engineering example，and the research results provide guidance for the selection of hydraulic supports of contiguous coal seam mining under room-and-pillar gob.