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 theimportant engineering issues that should be studied for arch dam design. The complicated geologicalconditions in the dam base (e.g. unconformable surfaces, faults and crannies etc.), dense drain holes, spacedistribution of curtains, and real simulation of boundary conditions etc. are the difficulties in the analysis ofarch dam base seepage field and seepage control measures. The method of finite difference is adopted, andthe crunode virtual discharge method of solving the seepage of free surface by fixed gridding and the drainhole fine solving technique are applied in this paper, multiple schemes of calculation and analysis are madeto the tridimensional seepage fields of Wanjiakouzi arch dam base, and study emphasis is given to the localor entire invalidation, crannied rock mass penetrability, curtain trend, length and depth, curtain penetrability,penetrability of unconformable surface of the main water transmission passage, and the impact of faultpenetrability on the seepage field, hence obtained the distribution rule of dam base seepage fields,decompression and drainage actions of impervious curtain and drain holes, seepage amounts of seepagepassages and drain holes, seeping gradient ratios at various locations of dam base and the seepage velocity.The main seepage characteristics of dam base seepage fields, macroscopical seepage control capability andlocal seepage control weakness are evaluated comprehensively. The study indicates the water headsdistribution of the dam base seepage fields and the uplift pressure on the construction basic surface aremainly controlled by the drain holes in dam base, hence, for the seepage control in dam base and thestability of dam body, it is critical to ensure the straightway of drain holes in the dam base. Theunconformable surface has a rather big impact on the seepage characteristics of dam base, therefore it issuggested to excavate as soon as possible to the extent below the unconformable surface, or to have thecurtain penetrated through the unconformable surface so as to raise the anti-seepage effect of the curtain.