The numerical simulation of the flow of an injected grout in underground room and pillar coal mines.

摘要

This research was conducted to develop a computer program, Groutnet , to simulate the flow of a grout injected in a room and pillar coal mine. Previous rheological investigations have demonstrated that grouts composed largely of coal ash and water are Bingham fluids. Because the simulation of a large scale grout injection operation by solving the three dimensional equations of motion would be prohibitively expensive, the equations of motion were integrated in the vertical direction, and the unsteady and convective acceleration terms in the momentum equations were neglected. In order to achieve a closed set of equations, a uniform flow equation was developed from the analytical solution for the flow of a Bingham fluid in a channel of infinite width.; The computer program Groutnet was written to solve these simplified governing equations with a finite difference method that is second order accurate in time and space. Groutnet has successfully simulated one and two dimensional hypothetical grout injection problems. This dissertation presents the results of several one dimensional simulations of channel flow to establish the basic validity of Groutnet's numerical algorithm. In order to establish the ability of Groutnet to properly calculate a non-uniform, horizontal velocity profile, the results of a two dimensional, Newtonian channel flow simulation are also presented. Because Groutnet does not include the horizontal shear stress terms in the approximated momentum equation for a Bingham fluid, a Newtonian grout was selected for the two dimensional channel simulation. The relative magnitude of the horizontal shear stress terms should be negligible in those situations where the depth is much smaller than the channel width.; Since Groutnet is intended to serve as a tool in the placement of boreholes for the injection of room and pillar mines, the results of several simulations of the spread of grout from a centrally located borehole are also presented. In addition to testing Groutnet's capabilities, these simulations establish the effect of mine geometry and material properties on the spread of an injected grout. The final two dimensional model presented is a realistic simulation of a relatively large scale grout injection operation using hypothetical input data.