1种改进的流变模型在层状覆盖层坝基上的应用*

为了深入剖析深厚覆盖层中各层岩土体的流变性对大坝安全稳定的影响机理。探索新的流变元件模型H-KS以适应层状覆盖层坝基，借助Comsol建立数值模型，计算青湾坝安全稳定指标，分析坝基流变对大坝整体的影响。研究结果表明:对于岩性、物理力学性质差异较大的层状覆盖层坝基，采用H-KS流变模型能较好反应大坝应力、变形和渗流实际情况，与监测值对比，误差在5%以内；相比不考虑流变的模型而言，应力、变形分别增大了10%和15.7%，部分增量会影响大坝结构的安全稳定，应予以重视；流变导致大坝整体渗透性降低，粗细粒层孔隙水压力分别减小了约50%和2.5%，加速了流固耦合过程，对于重新评估大坝的渗透性有重要参考意义；由于流变性不同，深厚覆盖层中粗粒土层在变形、应力和渗流方面影响最大，细粒土的贡献相对较小，除了与岩性相关之外，还与土层所处位置、厚度等相关。研究结果可为层状覆盖层上的大坝安全稳定体系的建立提供理论支持。

Application of an improved rheological model on dam foundation on layered overburden

In order to deeply analyze the influence mechanism of rheological properties of rock and soil on the safety and stability of dam in deep overburden layer,a new rheological element model H-KS was explored to adapt to the dam foundation on layered overburden.With the help of Comsol,a numerical model was established to calculate the safety and stability index of Qingwan dam,and the influence of dam foundation rheology on the whole dam was analyzed.The results showed that for the dam foundation on layered overburden with large difference in the lithology and physical and mechanical properties,the H-KS rheological model could better reflect the actual situation of the dam stress,deformation and seepage.Compared with the monitored values,the error was within 5%.Compared with the model ignoring the rheology,the stress and deformation increased by 10% and 15.7%,respectively,and part of the increment would affect the safety and stability of the dam structure,which should be paid attention to.The rheology caused the decreasing overall permeability of the dam,and the pore water pressure of the coarse-grained and fine-grained layers reduced by about 50% and 2.5%,respectively,and it accelerated the fluid-solid coupling process,which had important reference significance for reassessing the permeability of the dam.Due to the different rheological properties,the coarse-grained soil layer in the deep overburden had the greatest impact on the aspects of deformation,stress and seepage,while the contribution of fine-grained soil was relatively smaller.In addition to being related to lithology,it was also related to the location and thickness of the soil layer.The research results can provide theoretical support for the establishment of dam safety and stability system on the layered overburden.