基于有限差分计算的某水库大坝渗流场稳定性分析

Analysis of the Seepage Stability of a Reservoir Dam Based on Finite Difference Calculation

为了对云南某水库大坝渗流稳定性进行评价分析,运用基于有限差分原理的Visual Modflow软件进行渗流场数值模拟。结果得出,坝体内部浸润线较低,稳定性较好;下伏地层二叠系灰岩岩溶裂隙发育,渗流速度较大,最大渗流速度出现在坝体上游坡脚处。此外,该坝体两侧后坝脚,沿管壁均有较集中的渗水点,说明坝体土与管壁的接缝处理较差,在长期渗水或在高水位情况下,将会进一步加剧接缝的扩大发展趋势,易导致管壁周边土体产生接触冲刷型的渗透破坏现象,进而影响水库运行及坝体稳定。针对所出现的问题,提出2点建议:一是增加坝基填土的厚度,防止库水过多渗入下伏地层,最大程度避免土体液化现象出现;二是严格监测二叠系灰岩地层中的岩溶现象,一旦出现较大规模的溶洞,应及时进行灌浆处理,以防地基出现坍塌下沉,从而威胁大坝的安全。

The seepage stability of a reservoir dam in Yunnan Province was analyzed. Numerical simulation oi seepage tleld was carried out by Visual Modflow software based on finite difference theory. Results showed that seepage line inside the dam was lower with better stability; there was karst fissure in underlayer permian limestone, which＂ had greater seepage velocity. The maximum seepage velocity appeared in the upstream toe of the dam. In addition, seepage points concentrated in both sides of the dam foots, indicating that the joint treatment was poor between dam earth and tube wall. Long-term water seepage at a high water level furtber expanded the juncture, easily led to the infiltration and sabotage phe- nomena in soils around the tube wall, and affected the reservoir operation and the dam stability. Based on these, two suggestions were put for- ward. First, the thickness of dam filling should be increased, so as to prevent excessive infiltration of reservoir water into the underlying strata, and to avoid the phenomenon of soil liquefaction in the greatest degree. Second, karst formation in underlayer permian limestone should be strict- ly monitored. Once the large karst cave appegrs, grouting treatment should be carried out on time in order to prevent ground subsidence and col- lanse, and to avoid the threatening to dam safety.