Optimization of face flexible bolting and grouting technology for longwall face support under difficult geological conditions

Abstract

Abstract Longwall face fall in the open face area is one of the most difficult ground control problems in mining thick coal seams in China especially under difficult geological conditions. This paper has proposed a new flexible bolting and grouting technology for face support. The flexible support method includes face support using flexible coir ropes and face grouting with cement and accelerator mixtures. Numerical and laboratory studies of pullout tests are performed to further improve the flexible support performance including optimization of boreholes and flexible bolts diameters, and selection of grouting materials. The results show that (a) The optimized rope‐borehole diameter ratio is around 0.5 to ensure the best face reinforcement; (b) The grouting material (a mixture of ultrafine cement, mineral powder and sodium silicate) shows advantages of low cost, effective waste disposal, reduced setting time, and good pullout limit force and is recommended for industrial application with sodium silicate at a proportion of 10% by weight and mineral powder at 30%. The application of the new flexible bolting and grouting method in Chenmanzhuang mine shows improved face stability and reduced capital cost.

Keywords

• face fall
• face reinforcement
• flexible bolting and grouting technology
• optimization
• pullout test