Key Technology Research Of Pre-support For Entry Roof Locates In Soft Surrounding Rocks

The construction of entries in thick coal layer from Zhaojiazhai Mine always leads to caving and roof falls,the research of pre-support was put forward to solve this problem.The calculation formula of fractured zone indicates that the caving frequency will decrease significantly by improving the cohesion and friction angle.The laboratory experiments proved that the cohesion,friction angle and shear strength of water saturated coal increased,while the compression strength decreased,which prevented the danger of caving.The slurry preparation was carried out to find the proportion of the main composition,the water ration,the type of water reducer and proportion,the type of early strength agent and proportion.The numerical simulation of slurry diffusion concluded the effective slurry diffusion time,the effective diffusion radius,the effective pore pressure index,the optimum slurry grouting pressure.It also analyzed the influence of stress state on the slurry diffusion,which indicated that higher lateral stress restrained the slurry diffusion.The research was used in a part of transportation entry of 12204 panel,where the drilling-sampling and observation in the roof showed that the integrity of roof improved apparently.