Seepage and exit gradient under impervious structures with two sheetpiles on layer of infinite depth

摘要

Seepage force represents one of the most common cause of failure of hydraulic structures. Several methods are available in technical literature to provide a good estimate of the factor of safety against seepage erosion. According to Terzaghi, the factor of safety can be determined comparing the exit gradient with the critical gradient. Obviously, the calculation of the critical gradient is very simple, while more complex is the evaluation of the exit gradient. In the present work is presented and discussed the analytical solution of the seepage under a structure with two sheetpiles, resting on the surface of a infinite, homogeneous and isotropic porous medium. A very general solution of the flow has been achieved by means of conformal mapping technique, applying the well-known Schwarz-Christoffel transformation; so, once the size of the structure and of the flow domain have been defined, the exit gradient can be calculated to perform a quick estimate of safety factor.