砾性土剪切波速特性与液化机理试验研究

liquefaction of gravelly soils is confirmed after the wenchuan earthquake even though controversy still exists on gravelly soil liquefaction mechanism. The current liquefaction assessment methods are not applicable for gravelly soils. However, the demanding for gravelly site liquefaction assessment increases constantly. This proposal is focusing on shear wave velocity properties of gravelly soils and the mechanism of gravelly soil liquefaction using many testing methods based on the gravelly soil liquefaction in Wenchuan earthquake. The main research activities are (1) developing a measuring method for the relationship between shear wave velocity and relative density of cohesionless soils using Bender Elements technique, and establishing the relationship between the shear wave velocity and physical indicators such as relative density, gravel contents and coarse grain size of gravelly soil; (2) analyzing the buildup mechanism of pore water pressure and strain progressing of gravelly soils in triaxial-stress state using large scale dynamic triaxial dynamic triaxial apparatus; (3) developing a measuring method for the distribution of lateral deformation of soils using FBG technique, and studying dynamic response, strain and pore pressure of gravelly soil using a 1g shaking table test; (4) providing a dynamic model of pore water pressure in gravelly soils and a dynamics analytical method of efficient stress in gravelly soils layers. The research results will provide theoretical basis for liquefaction evaluation and prevention of gravelly sites, serving for "One Belt and One Road" national development strategy.

砾性土液化在汶川地震后被证实，而其机理研究尚存矛盾且现行规范无法判别其液化，研究现状不能满足工程需求。剪切波速是相关研究的有效思路。本项目拟以砾性土地震液化为背景，通过多种试验手段，从四个方面研究砾性土的剪切波速特性与液化机理：（1）研发基于弯曲元技术的无粘性土剪切波速与相对密度联合测试系统，研究砾性土的剪切波速与其相对密度、含砾量、粗料粒径等物性指标的定量关系；（2）应用GDS大型动力三轴仪研究三轴应力状态下饱和砾性土的动强度、应变发展规律及孔压增长模式；（3）研发基于光纤光栅技术的模型土体内部变形量测方法，并通过振动台试验研究1g重力状态下饱和砾性土模型的动力响应、应变发展规律及孔压增长模式；（4）研究砾性土地震液化孔隙水压力增长模型，发展相应的有效应力分析方法。以期项目研究成果能为砾性土场地的液化判别、灾害防治等相关工程应用提供理论依据，为“一带一路”国家发展战略的工程建设服务。

经过本项目负责人所属研究团队十年的探索研究与积极推动，砾性土的液化概念及风险已逐渐被工程界和学界所接受。本项目是砾性土液化研究课题的一部分，旨在探索砾性土的剪切波速特性及其液化机理，为剪切波速方法应用于砾性土场地的液化判别的合理性探索理论基础。项目研究目标基本实现。研发了适用于砾性土的剪切波速与相对密度联合测试仪；定量分析了相对密度、含砾量等因素对剪切波速的影响；推动的以橡皮膜顺便性为核心的砾性土单元体试验方法及饱和技术和应变测试为主的模型试验方法研究；探索了砾性土在循环荷载作用下的超静孔压和应变响应规律。将研究方法和成果推广到岛礁工程场地的动力特性研究中，并着眼于开发在珊瑚土场地的液化判别方法等研究中的应用前景。