Abstract
In order to effectively control the large deformation of coal pillar and roadway while entry retained along gob side with small coal pillar, taking 1311 and 1312 working face of a coal mine in Shanxi Province as engineering background, the structural characteristics of overlying rock of entry retained along gob side with small coal pillar are studied comprehensively by means of theoretical analysis, numerical simulation and industrial test, and the stress source of entry retained along gob side with small coal pillar and the principle of roof cutting and pressure relief by shaped charge blasting with combined and grouped of deep and shallow holes are analyzed, then the roof cutting and pressure relief technology of shaped charge blasting with combined and grouped of deep and shallow holes and the cooperative control scheme of small coal pillar are put forward. Combined with the geological conditions of 1311 working face, through the calculation of caving zone and crack zone height of working face, the analysis of roof breaking and instability conditions and the calculation of crack zone radius during blasting, the key parameters of roof cutting by deep and shallow hole combined blasting are determined. Through the numerical simulation and analysis of roof cutting and pressure relief of different key stratum, the vertical stress in small coal pillar under different foor cutting height is as follows: uncut roof > only cut layer 2 > only cut layer 1 > cut layer 3 + partial layer 2 > cut layer 1 ~ 3; on this basis, a cooperative control scheme of "roof cutting and pressure relief by shaped charge blasting with combined and grouped of deep and shallow holes" + "anchor-cable combined support" + "coal pillar strengthened" is put forward. The field industrial test results show that the control effect of small coal pillar and roadway surrounding rock is good.