深厚覆盖层上高土石坝的动力稳定分析

在高地震烈度区修建深厚覆盖层上的高土石坝面临许多新问题,如大坝的动力稳定、坝基液化问题等。以直粘土心墙及坝基截渗墙土石坝为例,采用三维动力固结有限元方法,研究强震区深厚覆盖层上的高土石坝的动力稳定问题。三维动力固结有限元程序以动力固结方程为基础,采用能够反应土体非线性、滞后性以及不可恢复性动变形特性的拟等效弹塑性本构模型,放弃了动孔压上升模式,在震动全过程中跟踪孔隙水压力产生、扩散和消散的发展变化,实现了动力渗流与动力反应分析的真正耦合,可较好地反映土体在地震过程中的实际性态,避免了动本构模型与动孔压模型有时难以合理搭配的问题。计算结果表明,深厚覆盖层上修筑的直心墙土石坝的静应力和静位移均较大,但它的动应力、动位移及加速度的反应值却均较小,且坝底的孔压比也较小,可满足稳定性要求。

DYNAMIC STABILITY ANALYSIS OF HIGH EARTH-ROCKFILL DAM ON THICK MORAINE COVER FOUNDATION

To build high earth-rockfill dam on thick moraine cover foundation in high earthquake intensity region will face many new problems such as dynamic stability,dam foundation liquefaction etc. As an example, three-dimensional dynamic consolidation FEM is employed to analyze the reaction of high earth-rock fill dam with clay core and cat-off wall. The dynamic stability is researched. An equivalent quasi-elastoplastic constitutive model which can express nonlinear viscid and un-recoverable deformation of soil is employed in the new dynamic consolidation FEM,while dynamic pore water pressure model is abandoned. The generation,diffusion and scatter of dynamic pore water pressure in a complete earthquake process are tracked. It is a real coupling of dynamic seepage and dynamic reaction. The calculation results show that the static stress and displacement of the dam on thick moraine cover foundation are bigger;the dynamic stress,displacement and acceleration are smaller;the ratio of pore water pressure in the dam base is smaller than the dam on rock foundation. The dam is safe.