降雨-地震共同作用下加筋土挡墙变形破坏演化机理及设计方法研究

It has been widely recognized that geosynthetic reinforced soil retaining walls (GRS-RWs) have good seismic performance. Previous research has shown that earthquakes and rainfall often occur together, their combined effect will decrease the stability of reinforced soil structures and trigger secondary disaster. In order to study it in-depth, the mechanical properties of unsaturated filling under rainfall-earthquake combined effect need to be focused, namely, the dynamic coupling effect between soil particles, water and air. This project aims to explore deformation and failure mechanism of GRS-RWs under rainfall-earthquake combined effect, and establish a corresponding dynamic design and calculation method. First, large-scale static/dynamic triaxial tests are employed to reveal the stress-strain relationship and deformation characteristics of the filling. Then apparent parameters and their development function, which can truly reflect the static /dynamic behavior of the filling, will be confirmed. On this basis, a unified saturated-unsaturated filling static/dynamic constitutive model can be established thereafter, which will be imported to a numerical analysis program to model real engineering cases. Finally, full-scale shaking table tests and numerical simulation will be carried out to reveal the evolution mechanism of deformation and failure of GRS-RWs under rainfall-earthquake combined effect, and a design and calculation method that can properly assess the dynamic response of GRS-RWs under considering the rainfall effect will be established. The research results can not only provide scientific evidence for the risk assessment of GRS-RWs, but also can provide technical support for controlling the deformation of GRS-RWs, meanwhile, existing design theories of reinforced soil structures can be improved as well.

加筋土挡墙良好的抗震性能已被广泛认同。历史震例表明：地震与降雨常相伴而生，其共同作用会削弱加筋土结构稳定性并引发次生灾害，对其进行深入研究需重点关注降雨-地震共同作用下非饱和填土的力学特性，即固、液、气三相之间动力耦合作用。本项目旨在探索降雨-地震共同作用下加筋土挡墙变形破坏演化机理及其设计方法。首先，通过大尺寸静/动三轴试验获取加筋土填土的应力-应变关系；继而探寻能够真实反映填土静/动力学行为的本构表征参数及其发展函数，建立饱和•非饱和填土统一静/动力本构模型，并将其导入数值计算程序中对工程实例进行数值分析；最后，结合足尺振动台试验和数值分析结果，揭示降雨-地震共同作用下加筋土挡墙变形演化规律及破坏机理，并提出可考虑降雨作用的加筋土挡墙动力设计计算方法。其研究成果不仅为加筋土挡墙的风险评估提供科学依据，而且为控制加筋土挡墙变形确保其稳定性提供技术支撑，同时还可完善现有加筋土结构设计理论。

加筋土挡墙作为一种新型挡土结构，因其良好的稳定性、经济性、抗震性能、施工便捷以及生态美观等诸多因素，已在公路、铁路以及水利等工程领域中得到广泛应用。历史震例表明地震与降雨常相伴而生，但目前国内外对降雨-地震共同作用下加筋土挡墙变形特性和稳定性研究还很少，尚缺乏机理性认识。本项目首先通过大尺寸静/动三轴试验和数值解析揭示加筋土填土的力学特性和应力-应变关系；在此基础上，开展了降雨、地震次序影响作用下的加筋土挡墙离心机振动台试验，探究了先降雨后地震、降雨和地震同时发生以及先地震后降雨3种工况条件下加筋土挡墙的变形特性和破坏模式；最后，结合振动台试验结果，采用DBLEAVES有限元数值分析程序探讨了筋材长度、刚度及加筋间距对降雨-地震荷载共同作用下加筋土挡墙稳定性的影响，完善了加筋土挡墙的动力理论。研究结果表明：对于先降雨后地震工况，雨水可充分渗流，孔压会逐渐消散，土体处于非饱和状态，基质吸力会增强挡墙稳定性；对于降雨和地震同时发生工况，雨水无法及时渗流，地震会使土体内部孔压迅速升高，极大降低了挡墙的稳定性；对于先地震后降雨工况，挡墙变形主要由地震导致，降雨对挡墙变形的影响并不明显；非饱和状态下破坏模式表现为墙体开裂，且裂缝位于筋材末端，而饱和状态下表现为面板鼓胀破坏；相对于加筋间距，筋材刚度对加筋土挡墙地震响应影响显著；增大筋材刚度可有效约束土体变形，其主要表现形式为筋材拉力明显增大；在保证筋材刚度足够的情况下，增大筋材长度可有效提高加筋土挡墙稳定性。研究成果不仅为加筋土挡墙的风险评估提供科学依据，而且为控制加筋土挡墙变形确保其稳定性提供技术支撑，同时还可完善现有加筋土结构设计理论。