Study on surrounding rock control technology for mining roadway of ultra-deep protective layer

The stability control of the mining roadway in the 1 300 m ultra-deep protective layer of Huafeng Colliery is a bottleneck problem affecting the safe and efficient production of the mine.Based on the comprehensive testing of on-site geomechanics and the study of the specific failure mechanism of surrounding rock,a combined support plan of ultra-high-strength heat-treated pre-stressed bolt with cable-grouting is proposed.The 700 MPa grade ultra-high-strength heat-treated bolt was developed with reaking strength of 850 MPa and an impact absorption power of 100 J;underground industrial test was firstly carried out in the 1 300 m deep coal mine roadway.The monitoring of multi-parameter changes such as roadway bolt support force,four-point roof separation and surrounding rock borehole stress was carried out on site,and the analysis obtained:under the disturbance of blasting excavation,the overall surrounding rock deformation is basically stable after a distance of 80 m from the front of the ultra-deep roadway;however,the deep stress of the surrounding rock still creeps for a long time and exhibits a large-scale increase and decrease cycle.The test results showed that,compared with the roof full-anchor cable support method,the mining face deformed ahead of the entire roadway.Reduce by 50%,and increase the efficiency of excavation support by 20%.