Physical model simulation of surface subsidence under sub-critical condition

Abstract

Physical modelling and numerical analyses are performed to assess the representativeness of some widely used profile functions developed to describe the subsidence configurations under sub-critical conditions. Synthetic gel is used to simulate the overburden. The surface profile measurements are used to calculate the maximum subsidence, slope and curvature angle. The model results agree well with those obtained from numerical analyses with discrepancies of less than 3%. Both suggest that the subsidence components increase with opening width-to-depth ratio. Under the same trough width, the trigonometric function slightly underpredicts the subsidence components, particularly for those induced by deep and small openings. The subsidence components predicted by the hyperbolic function are about 10% greater than those of the physical models. The exponential function underestimates the model measurements by about 5% for all cases. A set of empirical equations is derived to fit with the test results, which can be used to predict the subsidence components induced by the mine opening. Based on the scale law, the gel properties and the opening depths and widths can be correlated with those of the prototypes representing overburden above salt and potash mines in the Maha Sarakham formation.