The entry retained along gob side with small coal pillar and its surrounding rock control: a case study

Abstract

Abstract In order to effectively control the large deformation of coal pillar and roadway during entry retained along gob side with small coal pillar, taking 1311 and 1312 working faces of a coal mine in Shanxi Province as engineering background, the structural characteristics of overlying rock are studied, and the stress source of entry retained along gob side with small coal pillar and the principle of roof cutting and pressure relief are analyzed, then the roof cutting and pressure relief technology of shaped charge blasting with combined and grouped of deep and shallow holes is put forward. According to the geological conditions of 1311 working face, through the calculation of caving zone and crack zone height of the working face, the analysis of roof breaking and instability conditions and the calculation of crack zone blasting radius, 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 in different key strata, the variation law of vertical stress acting on small coal pillar is obtained, as follows: no roof cutting > only cut layer 2 > only cut layer 1 > cut layer 3 + partial layer 2 > cut layer 1 ~ 3; Based on these, 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.

Keywords

• Entry retained along gob side with small coal pillar
• Multi-key stratum
• Stress source
• Shaped charge blasting with combined and grouped of deep and shallow holes
• Roof cutting and pressure relief