Research On The Unsteady Seepage Of The Well-Row And It’s Calculation By FEM Method

The relief well(multiple wells) is an important measure for the seepage control, which has been widely used in geotechnical engineering. The relief well group is often used to reduce the pressure of confined water, which is usually in the state of unsteady flow. As far as now, the steady flow situation has been perfectly solved; but the unsteady flow situation and its calculation has remained unsolved. As a kind of common groundwater type, the confined water is often confronted with pressure-reduction process in a unsteady state, so the problem is in evidence.On the base of making a summary of the calculation of single well and the well-group, this issue has used the so-called virtual bypass method to simulate the resistance of well row, and also made a research on the expression of the length of the additional flow path, which is a very critical parameter in the unsteady flow situation. Considered on the engineering application, the author also made FEM program to slove the "fixed-flow" and "fixed-drawdown" situation, which has solved the calculation of orderly-distributed well group.The correctness of FEM program has been proved by making a contrast with the analytic solution. The result shows that, fixed-flow FEM program has a highly correction and precision, while, if a suitable time step has been selected, the fixed-drawdown FEM program could also give a satisfactory result, with merely acceptable error spectrum.In order to make use of the FEM program on engineering, some usually occured instances has been offered to show how the program can be used and what kind of problem can be solved.