高堆石坝心墙渗流特性离心模型试验研究

Centrifugal model test on seepage characteristics of high core rockfill dam

高土石坝在施工期心墙会产生超静孔隙水压力,且难以有效消散,蓄水后心墙从非稳定渗流状态到稳定渗流状态,因此,渗流特性异常复杂。目前,有限元方法进行渗流计算不能考虑施工期引起的孔隙水压力,因而不能完全了解土石坝的渗流特性。长河坝为砾石土心墙堆石坝,最大坝高为240 m。利用离心模型试验技术,通过分析长河坝施工期和运行期心墙的孔隙水压力的产生和消散变化规律研究大坝心墙的渗流特性。试验结果表明,心墙孔隙水压力经历施工时的增长期、竣工后的消散期、非稳定渗流时的增长期和消散期、稳定渗流时的稳定期5个阶段。心墙高程不同、填筑含水率不同,各阶段的孔隙水压力和历时也不同。心墙位置越高或填筑含水率越大,施工期孔隙水压力系数越大,形成稳定渗流所需时间越短。心墙位置越高或填筑含水率越小,心墙位势越大,非稳定渗流期心墙位势大于稳定渗流期。研究成果对高心墙堆石坝设计和施工具有指导意义。

Excess pore water pressure will be generated in the core during the construction of high rockfill dam, and it dissipates slowly. After water storage, the core will change the unsteady seepage state to the steady flow state; so the seepage characteristics are very complicated. The pore water pressure generated during construction can not be considered in the finite element method for seepage calculation; and the seepage characteristics of earth-rock dam can not be fully understood. Changhe Dam is a gravelly soil core rockfill dam, with maximum height of 240 m. Centrifuge modeling tests are carried out to study the seepage characteristics of Changhe Dam through analyzing the generation and dissipation of pore water pressure in construction and operation periods. Test results show that the pore water pressure would go through periods of generation in the construction, the dissipation after construction, the generation and dissipation in the unsteady seepage state, the stabilization in the steady seepage state. The pore water pressure and duration of each period are influenced by the position and filling water content of the core. The higher the position or filling water content of the core is, the larger the coefficient of pore water pressure during construction is, the shorter the duration of steady seepage is. The higher the position or smaller filling water content is, the larger the potential is. The potential in unsteady seepage state is larger than that in steady seepage state. It is instructive for design and construction of high core rockfill dam.