APPLICATION OF ROOF BOLTING TECHNOLOGY FOR MINE WORKINGS IN GAS- AND WATER-BEARING ROCKS

Abstract

Purpose. To substantiate the use of roof bolting for mine workings as a technological way to reduce gas and water inflows into mine workings and to develop the method of reducing water inflow with the use of combined frames and bolts supporting. Methodology. Numerical modelling method for coupled processes of rock mass strain and fluid filtration has been applied. The model is based upon fundamental ideas of mechanics of solids and filtration theory. The problem has been solved using a finite element method. The influence of stress field on formation of the filtration area, the effect of changes in fluid pressure on stress state and decrease in the strength properties of rocks during soaking (in the case of water filtration) were taken into account at each time iteration. Results. A study of the influence of supporting mine workings on filtration permeability caused by its driving has been performed. It is shown that the use of roof bolting restrains the process of cracking in the area affected by mining. At the same time the sizes of the filtration area are considerably reduced, permeability in this area decreases. Roof bolting allows to reduce the average filtration permeability caused by the redistribution of the stress field during the driving of mine working by 15 times or more. The influence of bolts on the process of fluid filtration has been studied. It is established that filtration process is actively taking place around the mine workings with frame support. When using roof bolting, methane from undermined gas sources is not involved in the filtration process. On the walls of the mine working, methane filtration intensity from the coal seam is significantly reduced. Roof bolting reduces water inflows into the mine workings in water-resistant rocks by 2.5 times, in non-water-resistant rocks by 3.4 times. Scientific novelty. For the first time the study of the influence of supporting type in mine workings on formation of the filtration area in the host rocks and the course of filtration processes has been performed. A method of reducing water inflows into mine workings with the use of combined frames and bolts supporting has been developed. It is shown that roof bolting can be used as a technological way to reduce gas and water inflows into the mine workings. Practical significance. Application of the proposed method leads to a significant economic effect by reducing the cost of water pumping and repair work to restore mine workings after emergency water inflows.