Numerical study of the interaction of rock bolts with the block-structured rock mass

In order to ground parameters of rock bolting for mine workings, it is necessary to study the stressedly-deformed state of the host rock and the elements of rock bolting. Under certain mining and geological conditions, the rock mass is broken by cracks and divided into blocks. Methods designed for modelling solid environments are not sufficient for the study of a block-structured rocks. In this regard, the purpose of this work was to develop a method of studying the state of block-structured rock mass around the mine working with rock bolting and to ground the possibility of preventing the rock blocks from sliding with the help of rock bolting structure. As a result of the work, a numerical model of a block-structured rock mass with a mine working supported with rock bolts, which were modeled using two-node rod finite elements, was developed. Cracks were simulated using a four-node contact finite element, which has zero thickness, and the initial coordinates of the nodes of its opposite sides coincide. The generation and growth of a crack can occur in the form of its opening or displacement along its surface. A method was developed, which, due to the introduction of special contact elements into the finite-element scheme, allows simulating the stressedly-deformed state of rocks with cracks. The use of the proposed method of studying the block-structured rock mass makes it possible to check the efficiency of the rock bolting elements during the development of the supporting scheme. Using the developed method, the relative displacement of the block formed in the mine roof was investigated in four cases: when the mine working is not supported, the mine working is supported with the use of simple, reinforced and powerful rock bolting structures. It was shown that in the cracked rocks divided into blocks, the displacement of the rock block reaches a maximum in the unsupported mine roof. The simple rock bolting structure almost does not prevent the rock block from shifting into the mine working space, together with a row of rock bolts installed vertically. The inclination of the rock bolts by 70° to the mine face in the reinforced rock bolting structure significantly improves the condition of the mine roof; its displacement is reduced by 87%. And the use of the powerful rock bolting structure blocks the movement of the rock-bolts block almost completely, by 93%. Therefore, the reinforced and powerful rock bolting structures allows you to keep the cracked rock mass divided into blocks in a stable condition. Keywords: block-structured rocks, mine working, rock deformation, rock bolting structure, numerical simulation.