Application of roof bolting to reduce water inflow into mine workings during the crossing of tectonic faults

Abstract

In this work, the problem of water inflow reduction in Ukrainian coal mines, which are distinguished by difficult hydrogeological conditions, was considered. A numerical study of the change in water inflow into a mine working when it crosses a tectonic fault was carried out. The cases when the permanent working was supported by frame supports and roof bolts were considered. The calculation of stress fields, zones with inelastic deformations and coefficients of permeability, which depend on the stress state and takes into account tectonic and natural permeability of the rocks, was performed. The results of calculating the water pressure and water inflow into the mine working in all considered cases are presented in the article. Analysis of the calculated data showed that a disturbed area, which covered water-bearing ricks, was formed in the roof of the mine working with the frame support. Within this area, water can move towards the contour of the mine working. The filtration permeability of the host rocks increases significantly when the mine face approaches the tectonic disturbance. The flow rate of water reaches critical values. The use of roof bolting restrains the unloading of the boundary rocks from the rock pressure and keeps them in a triaxially compressed stress state. The permeability value decreases by the value of its technological component. In different areas of the intersection of tectonic disturbance, the water inflow into the mine working with roof bolting is 3-8 times less than in the working, supported by frame supports. Therefore, the use of roof bolting allows not only to keep the mine working in a stable state, but also to significantly reduce water inflows at complicated hydrogeological conditions.