Study On Key Techniques In Numerical Computation Of Unsteady Saturated-Unsaturated Seepage Field And Its Application

Targeting the service to the construction of hydraulic and geo-technical engineering in China, this paper puts comparatively deep research on the difficult points of the key techniques hi solving unsteady saturated-unsaturated seepage field. The main research contents and the results are as follows.(1) The study on the seepage properties of complex seepage field is launched. The emphasis is put on the influence of rainfall infiltration, unsaturated vaporization and infiltration surface and densely distributed holes to the seepage properties of hydraulic and geo-technical engineering. The mode and mechanism of the influence of the boundary conditions on the engineering seepage properties has been largely discerned.(2) On the basis of the method of invariable mesh & virtual flux of node, the improved nodal virtual flux is presented for the seepage problem with free face. Meanwhile, the precise mathematical description is given for the processing of vaporization and infiltration surfaces, pure virtual elements and transitional elements.(3) The robust numerical simulation method is presented for the quantitative analysis of the effect of unsaturated vaporization and infiltration surface. It is especially of significance for slope and agricultural hydraulic engineering.(4) The 3-D unsteady saturated-unsaturated seepage numerical program CIESUS-3D considering rainfall infiltration and unsaturated vaporization & infiltration is developed. And also, the steady saturated seepage numerical program PSSS-3D particularly in solving the seepage problem with free surface is coded. Meanwhile, some FEM accelerating techniques are discussed.(5) Based on the evaluation of present numerical simulation of drainage holes, the all-refined simulation technique precisely simulating densely distributed drainage holes is presented and deeply studied. The technique does not have any simplification of drainage holes, hi this paper, discussions are mainly conducted on the substructure mesh dividing and its second tune automatic dividing, the substructure shape, the continuity among substructures and general elements, the classification and definition of the integrated hydraulic model of drainage substructure, the iteration computation of water level inside drainage hole, the application of the technique in solving unsteady unsaturated seepage field, etc., therefore, the high efficient, precise and quantitative analysis of the complex seepage with densely distributed drainage holes is totally realized.(6) The substructure numerical programs CIESUSS-3D and PSSSS-3D are respectively developed based on the programs CIESUS-3D and PSSS-3D, introducing the all-refined simulation technique precisely simulating densely distributed drainage holes. With the application of PSSSS-3D to Jiangkou arch dam project, the complex seepage field of the dam foundation was successfully solved and analyzed, and the seepage control schemes were thenimproved.(7) The improving technique research of the drainage substructure method is performed. The repeated drainage substructure method, the multi-layer drainage substructure method and the adaptive drainage substructure method are presented. The 2-layer drainage substructure numerical programs CIEUSS-MULTI-3D and PSSSS-MULTI-3D and the adaptive drainage substructure numerical programs CIEUSS-SAA-3D and PSSSS-SAA-3D are developed based on the programs CIEUSS-3D and PSSSS-3D. Consequently, the computation precision and efficiency is effectively enhanced.(8) The research of back analysis of seepage field with complex boundary conditions is launched. On the basis of the traditional genetic algorithm, the improved accelerating genetic algorithm (IAGA) is presented, and the program IAGA-OPT concerning the algorithm is developed.(9) With the application of the all-refined simulation technique precisely simulating densely distributed drainage holes and the IAGA, the optimization method of seepage prevention and drainage structure design in hydraulic and geo-technical engineering is studied...