下分层停采线外延后回撤通道顶板预裂卸压研究

Research on Precracking and Pressure Relief of Top Plate of Retraction Channel after Extension of Lower Layered Stop Mining Line

分层开采时,当上分层已经回采完毕,为了对下分层尽量多回收煤炭资源,需要下分层安全通过上分层停采线后,继续向前外延回采。为了避免下分层外延的末采期间发生矿压灾害,需保证下分层的采空区顶板能够及时冒落。因而提出了工作面外延末采时伪斜调整渐进式通过上分层停采线,此外在上覆顶板采用水力压裂超前预裂的方式,对坚硬厚层砂岩弱化卸压。结果表明:下分层在安全通过上分层停产线后又安全外延回采了70 m,多回收煤炭资源近3万t;采用水力压裂对下分层外延后的顶板致裂卸压后,顶板厚层砂岩能够及时垮落,垮落的周期来压步距小于15 m,未发生矿压灾害,保证了安全生产。

During layered mining,when the upper layer has already been fully mined,in order to recover as much coal resources as possible from the lower layer,it is necessary to safely pass through the upper layer stop line and continue to extend the mining forward.In order to avoid mining pressure disasters during the final mining period of the lower layer extension,it is necessary to ensure that the roof of the goaf in the lower layer can fall in a timely manner.Therefore,a pseudo oblique adjustment progressive approach was proposed for the final mining at the extension of the working face,which passed through the upper layer stopping line.In addition,hydraulic fracturing was used for advanced pre fracturing on the overlying roof to weaken and relieve pressure on hard and thick sandstone layers.The results showed that after safely passing through the production line of the upper layer,the lower layer safely extended the recovery by 70 m,resulting in an additional recovery of nearly 30000 tons of coal resources;After hydraulic fracturing is used to crack and relieve pressure on the top plate after the extension of the lower layer,the thick sandstone layer on the top plate can collapse in a timely manner.The collapse cycle and pressure step distance are less than 15 m,and no mining pressure disasters occur,ensuring safe production.