Research on technology of excavating under roof then mining along bottom in soft and thick coal seam

In order to solve these problems that the roadway support job is very difficult and the repair work is heavy when excavating and mining along the bottom of soft and thick coal seam the new mining technology of excavating under hard roof and then mining along the bottom of the coal seam by digging the bottom coal to increase the height of roadway was put forward.Combining the geological conditions of the working face No.23302 in No.2 Yungaishan Mine,a combined support method using “bolt-mesh-cable+wooden pile+tent with single hydraulic props” was proposed to support the super-high roadway,which was used for mining along the bottom.At the same time,the models of coal loss caused by two mining methods of “mining and excavating along bottom” and “excavating under roof then mining along bottom” were established.The results show that two mining methods have the approximate coal loss in the condition of mining the coal seam with 7 meters thickness at one time.However,the technology of “excavating under the roof then mining along bottom” can greatly improve the efficiency of working face layout,reduce roadway deformation,and reduce support cost,which has an important reference value for the similar type of mine.