Diagnostics of anti-seepage screen at a tailings dam in permafrost based on the solution of an inverse problem by piezometric measurement data

We suggest a nonlinear geomechanical model of rock mass in the vicinity of a tailings dam in the permafrost zone at the Kumtor Mine in the Kyrgyz Republic. The model takes into account information on the structure of the object and the data on the deformation, strength, thermophysical, and filtration characteristics of frozen and thawed ground, as well as on the seasonal oscillations of air temperature. The numerical experiments show that, under unchanged external conditions, rock mass properties, and the position of the neutral layer, the zero isotherm, separating the frozen and thawed rocks, attains a stationary position in 12–15 years after the filling of the tailings pond and that a slight rupture of the anti-seepage screen can result in a large damage zone in the dam. Synthetic data are used to illustrate the solvability of the boundary value inverse problem of finding the time and place of the rupture in the anti-seepage screen from piezometric measurements in a few observation holes.