Numerical Simulation of Surface Subsidence After the Collapse of a Mine

Surface subsidence is a concern for many underground mining activities. If not predicted, this phenomenon can cause severe infrastructure damage. In this paper, a computer model is used to predict surface subsidence after the controlled collapse of a coal mine at Naburn in North Yorkshire, England. Scarcity of data on the characteristics of deep underground distressed and caved zones around coal mining excavations makes the numerical prediction of mining-induced subsidence very difficult. The authors derive appropriate input parameters for the numerical model using available borehole data with all necessary justifications provided. Simulations are performed using the commercial software FLAC3D. Different constitutive models, such as Mohr-Coulomb, modified Hoek-Brown, strain-softening, double-yield, and modified Cam-clay are used to obtain surface subsidence profiles, which are compared against measurements taken at the site. Special attention is given to numerically simulating processes involved in the underground movements. It is shown that none of the models listed above can reasonably predict the surface subsidence profile.