ANALYSIS AND STUDY OF TRIDIMENSIONAL SEEPAGE FIELD ATTHE DAM BASE OF WANJIAKOUZI ARCH DAM

摘要

The seepage characteristics and seepage control measures of the arch dam base are among thernimportant engineering issues that should be studied for arch dam design. The complicated geologicalrnconditions in the dam base (e.g. unconformable surfaces, faults and crannies etc.), dense drain holes, spacerndistribution of curtains, and real simulation of boundary conditions etc. are the difficulties in the analysis ofrnarch dam base seepage field and seepage control measures. The method of finite difference is adopted, andrnthe crunode virtual discharge method of solving the seepage of free surface by fixed gridding and the drainrnhole fine solving technique are applied in this paper, multiple schemes of calculation and analysis are madernto the tridimensional seepage fields of Wanjiakouzi arch dam base, and study emphasis is given to the localrnor entire invalidation, crannied rock mass penetrability, curtain trend, length and depth, curtain penetrability,rnpenetrability of unconformable surface of the main water transmission passage, and the impact of faultrnpenetrability on the seepage field, hence obtained the distribution rule of dam base seepage fields,rndecompression and drainage actions of impervious curtain and drain holes, seepage amounts of seepagernpassages and drain holes, seeping gradient ratios at various locations of dam base and the seepage velocity.rnThe main seepage characteristics of dam base seepage fields, macroscopical seepage control capability andrnlocal seepage control weakness are evaluated comprehensively. The study indicates the water headsrndistribution of the dam base seepage fields and the uplift pressure on the construction basic surface arernmainly controlled by the drain holes in dam base, hence, for the seepage control in dam base and thernstability of dam body, it is critical to ensure the straightway of drain holes in the dam base. Thernunconformable surface has a rather big impact on the seepage characteristics of dam base, therefore it isrnsuggested to excavate as soon as possible to the extent below the unconformable surface, or to have therncurtain penetrated through the unconformable surface so as to raise the anti-seepage effect of the curtain.