Numerical modeling of horizontal drain drainage in an open pit slope

A study has been made to evaluate the effects of horizontal drain drainage on the water table drawdown in open pit slopes. Two major parameters of a horizontal drain drainage system, length and spacing, were studied. A two dimensional finite element computer model was constructed to simulate the water flow into drains in rock slopes. Water flow in the saturated zone was assumed. The computer model was tested by the field data obtained from the LORNEX Mine in British Columbia and the data taken from INTRODUCTION TO GROUNDWATER MODELING (Wang & Anderson, 1982). Satisfactory agreements were obtained. As the result of computer simulations, a series of graphs were plotted. These graphs show the relationship between hydraulic head distribution vs. drain spacing and length. They could be used in horizontal drain design as an aid to determine the spacing and length of a drain system. The computer simulations were also made to study the drainage characteristics of anisotropic rock slopes. The results indicated the influence of such rock conditions on the drainage effect. Another feature of mining slopes is that their height varies as the mining operation progresses. Therefore, the suitable vertical spacing between drain rows was investigated by computer simulation. A comparison of the drainage effects of different drain patterns, parallel drain and fanned drain layouts, was also made.Applied Science, Faculty ofMining Engineering, Keevil Institute ofGraduat