Mining pit migration of an alluvial channel: experimental and numerical investigations

Abstract

ABSTRACT Sand mining changes river morphology, which alternatively has adverse impact on hydrology, environment, and ecology of the river system. Quantitative analysis of migration speed of pit and erosion in the mining zone is necessary for both sustainable mining operation and channel bed stability. Sediment transport mechanism in a river also gets affected due to in-stream mining activities. In this research a numerical model has been developed to estimate migration of mining pit by using flux vector splitting finite difference scheme. One-dimensional shallow water hydrodynamic equations and sediment mass conservation equation of bed material for equilibrium bed load sediment transport have been used for simulation of channel bed profile. Here, the applicability of various bed load transport formulation on pit migration has been studied. The use of different bed load transport formulation shows different migration speed of mining pit and downstream erosion. The model is verified by using laboratory flume experiment data for mining pit migration of rectangular and trapezoidal pit. High-resolution experimental data of bed profile obtained from ultrasonic ranging system shows migration and downstream erosion of mining pit. Numerical model developed in this study manifests good agreement with the characteristics of propagation of mining-induced erosion for different bed load transport formulation, while quantitative agreement is achieved only for the Van Rijn approach of bed load transport equation as a closure of the governing equations. The present experimental and numerical analysis shows that channel morphology due to mining can be predicted by using one dimensional numerical model within the acceptable limit.