伸缩缝防渗结构聚脲基涂层剥离破坏研究

水工建筑物普遍存在伸缩缝渗漏破坏问题,其破坏机理亟待研究。本文基于南水北调工程实际背景,引入损伤断裂力学理论,建立了内聚力单元的有限元仿真模型,并根据防渗涂层剥离试验的反向压力-位移变形数据,给出了适合于聚脲基复合防渗体系黏接层内聚力单元的刚度和黏聚系数等参数。计算了剥离反向压力,分析了聚脲基防渗涂层厚度对剥离临界反向压力的影响,以及水压力和伸缩缝扩展位移工况下,涂层厚度、涂层弹性模量和内聚力单元切向黏接强度对涂层剥离破坏长度的影响。数值计算结果表明,剥离反向压力与剥离试验的结果基本一致,说明内聚力模型参数的合理,能够有效模拟聚脲基复合防渗涂层剥离破坏的力学机理。同时,水压力和伸缩缝扩展位移工况下的分析结果,也说明了建立的聚脲基防渗涂层破坏分析方法对伸缩缝的防渗设计具有定量的指导作用。

Study on the polyurea-coat debonding failure of impervious structurein contractionjoints

Leakage failure of contractionjoints is extensively found in hydraulic structures and the studies on the failure mechanism are urgently needed to guarantee the regular service and maintenance of these structures.In this paper, based on the South-to-North Water Diversion Project and the damage and fracture mechanics, the finite element method with cohesive zone model(CZM) is used to analyze the failure process of polyurea-composite impervious coat in the contraction joints. According to the load-displacement deformation data obtained from impervious coat debonding experiments, the interface stiffness and viscosity coefficient for the adhesive layer cohesive elements are calibrated. In the numerical examples, we determine the critical loads of debonding of the coat and we also discuss the effect of the thickness of polyurea-composite impervious coat on debonding critical loads. Furthermore, the effects of the thickness, elasticity modulus of coat and shear stress of cohesive elements on the lengthof coat debonding when the water pressure is applied on the open contraction joint are included in our discussion as well. The numerical results show the consistency of debonding loads obtained from FEM simulation and experiments, which demonstrate the rationality of the parameters of the CZM and the validity of the mechanism of polyurea-composite impervious coat debonding failure. From the analysis results for the case that the water pressure is applied on the opened contraction joint, the proposed method for the failure analysis of the polyurea-composite impervious coatcanbe used for quantitatively reference to the impervious design of contraction joints.