深覆盖层上高堆石坝面膜防渗体界面力学特性研究

Geomembrane surface barrier of rockfill dam on thick riverbed alluvial deposit has many advantages, such as strong ability to adapt differential deformation, short construction period, low cost, saving land, low carbon and environment protection. However, the mechanical property of interface between geomembrane and contact materials has not been systematically revealed. There is still no scientific and reliable basis for design and stability analysis of the geomembrane surface barrier and the stress and deformation calculation of geomemrane. In this program, the methods of inclined plane test, pull-out test, thory deduction combined with numerical analysis and model test are employed to investigate the mechanical property of interface included in the geomembrane surface barrier for rockfill dam on thick riverbed alluvial deposit. Firstly, inclined table tests will be conducted to study the proterty of short-term shear strength and long-term shear strength considering the creep effect of fiber of interfaces between composite geomembrane and protection layer and cushion inculed in surface barrier of rock-fill dam, and then the mechanism of instability and failure of the surface barrier will be revealed. Secondly, the improved pull-out test method will be employed to investigated the property of shear stress and shear displacement and distribution on the interface between composite geomembrane and granual material cuhion in the anchorage structure on the dam foundation. Thirdly, synthesize tests results and the results of thory deduction, the shear strength criterion of interface included in surface barrier of dam and the constitutive model of interface in the anchorage structure will be established. Finally, the stability analyzing method of geomembrane surface barrier will be proposed, and the interface constitutive model will be used to numerically calculate the stress and strain of geomembrane by numerical implementation. And the constitutive model and numerical results will also be verificated by the model tests. The final objective of this program is to provide scientific theory basis for engineering design and safety assesment of geomembrane surface barrier for high rockfill dam on thick riverbed alluvial deposit.

深覆盖层上堆石坝面膜防渗体具有适应差异变形能力强、施工期短、造价低、节约土地及低碳环保等优点。然土工膜与接触材料界面力学特性尚未揭示，坝面防渗结构设计、稳定性分析及土工膜应力变形计算尚无据可依。本项目拟用界面斜板仪及拉拔试验、理论推导、数值分析和模型试验结合的方法对深覆盖层上高堆石坝面膜防渗体界面力学特性进行研究。首先，运用斜板仪对坝面防渗结构复合膜与保护层、垫层界面短期及考虑纤维蠕变效应下长期强度特性和失稳破坏机理进行研究；其次，运用改进拉拔试验方法对坝基锚固部位复合膜-散粒体垫层界面应力变形特性及分布规律进行研究；再次，综合试验结果及理论推导建立坝面防渗结构界面抗剪强度模型及坝基锚固部位土工膜界面本构模型；最后，提出坝面防渗结构稳定性分析方法；通过二次开发实现锚固部位土工膜应力变形计算与分析并用模型试验进行验证。本项目旨在为深覆盖层上高堆石坝面膜防渗体设计与安全评价提供理论基础和依据。

深覆盖层上堆石坝面膜防渗体具有适应差异变形能力强、施工期短、造价低、节约土地及低碳环保等优点。然土工膜与接触材料界面力学特性尚未揭示，坝面防渗结构设计、稳定性分析及土工膜应力变形计算尚无据可依。本项目采用接触面剪切试验、理论推导、数值分析和模型试验结合的方法对深覆盖层上高堆石坝面膜防渗体界面力学特性进行了系统研究。取得主要成果如下：.（1）运用斜板仪和直剪仪试验对坝面防渗结构中不同土工膜与垫层材料界面力学特性特性进行了试验研究，获得了不同土工膜与垫层界面的抗剪强度随法向压力、垫层类型、垫层表面粗糙度等因素影响下的变化规律及特性，揭示了土工膜界面受力变形特性及破坏模式。.（2）运用改进拉拔试验方法对坝基锚固部位复合膜-散粒体垫层界面应力变形特性及分布规律进行研究；开展了锚固部位土工膜受拉变形特征及破坏机理的结构模型试验研究。提出了能考虑土工膜变形影响的界面拉拔试验方法，并通过系统试验重点揭示了上覆压力、土工膜埋深及拉拔速率等因素对界面剪切变形及强度特性的影响规律，以及土工膜沿拉拔界面受力变形分布规律及拉伸变形破坏机理。.（3）综合土工膜界面力学特性试验结果及理论推导建立了土工膜界面本构模型。提出了坝面防渗结构稳定性分析方法；进行了复合膜-散粒体垫层界面本构模型研究及其在FLAC3D软件中的二次开发，在此基础上提出了高堆石坝土工膜防渗结构受力变形数值计算方法，并结合工程实例对深覆盖层上高堆石坝面膜防渗体受力变形特性及破坏机理进行了数值分析。研究成果为深覆盖层上高堆石坝面膜防渗体设计与安全评价提供了理论基础和依据。