基于改进流变元件模型的层状深厚覆盖层流变对面板坝结构性能影响的数值分析

Numerical Analysis of the Influence of Rheology of Layered Deep Overburden on the Structural Performance of Concrete Face Rockfill Dam Based on Improved Rheological Element Model

在深厚覆盖层上建造面板堆石坝,除考虑水-土流固耦合外,还应考虑坝基流变的影响。为了更好地模拟坝基流变对大坝及渗控体系的真实受力,基于深厚覆盖层所呈现出的层状特性,首先改进新的流变元件模型H-KS以适应层状覆盖层,然后借助Comsol建立流变与流固耦合模型,最后按时间顺序计算了河口村面板坝各阶段的力学指标,分析了坝基流变对大坝及防渗体系的影响。结果表明:对于各向异性明显的层状坝基,采用H-KS流变模型能较好反映大坝各阶段的应力、变形和渗流实际情况,误差均在5%以内;计算结果相比不考虑流变的DuncanE-B模型,应力和变形均增大11.8%以上,部分增量对大坝结构的安全稳定造成影响;填筑期的沉降和应力总量占比达70%以上,但单位时间增量却较小,如沉降增量仅为0.015m/月;蓄水期的岩土体流变及流固耦合作用对大坝各部位强度和刚度影响最大,应力及沉降增长率分别为0.02MPa/月、0.038m/月;运行期的各指标增长率逐渐趋缓,最终趋于稳定,但变形和应力增量可能会导致主要结构失稳或破坏。混凝土面板-趾板-连接板-防渗墙是完整、有效的渗流控制体系,坝基流变导致防渗墙上部水平位移增大,整体强度降低;趾板和面板在中部有受弯破坏的趋势。层状岩土体流变具有时效性,该层状坝基的流变在蓄水后2~3a间基本完成,相应指标也趋于稳定。研究结果对层状覆盖层上的面板坝安全稳定体系的建立提供了理论支持。

In the construction of concrete face rockfill dams on deep overburden,it is important to consider the influence of dam-foundation rheology in addition to the fluid-solid coupling of water and soil.To better simulate the real stress of dam-foundation rheology on the dam and its seepage control system,the new rheological element model,H-KS,is refined based on the layered characteristics of deep overburden.Hence,a rheological and fluid-solid coupling model is established using Comsol.Mechanical indices for each stage of the Hekoucun concrete face dam are then calculated chronologically,analyzing the influence of dam-foundation rheology on the dam and seepage control system.Results indicated that for the layered dam foundation with noticeable anisotropy,the H-KS rheological model more accurately reflects the actual stress,deformation,and seepage conditions of the dam at each stage,with an error within 5%;Compared to the Duncan E-B model,which does not account for rheology,the stress and deformation have increased by more than 11.8%,and some of this increase affects the safety and stability of the dam structure.The total settlement and stress during the filling period account for more than 70% of the total,though the unit-time increases are minimal,e.g.,the settlement increment is only 0.015 m/month.The rheology and fluid-solid coupling of the dam rock and soil during the impoundment period significantly impact the strength and stiffness of each part of the dam,with stress and settlement unit-time growth rates of 0.02 MPa/month and 0.038 m/month,respectively.The growth rate of each index during the operation period gradually slows and eventually stabilizes,but the increases in deformation and stress may cause the main structure to become unstable or damaged.The concrete panel-plinth-impervious wall forms a complete and effective seepage control system.The rheology of the dam foundation increases the horizontal displacement of the upper part of the impervious wall and reduces the overall strength;the plinth and the panel are prone to midsection bending damage.The rheology of layered rock and soil exhibits time sensitivity,with the rheology of the layered dam foundation largely completed within 2-3 years after water storage,and the corresponding indicators tend to stabilize.These results provide theoretical support for the establishment of the safety and stability system of the face dam on the layered overburden.