砾性土层液化影响因素初步研究

发布时间：2018-07-18 17:08

【摘要】：2008年汶川地震前,国内外砾性土液化实例报道很少,砾性土液化问题没有引起学术界和工程界的注意。工程上通常认为砾性土的渗透性较好,地震中产生的超孔压很容易消散,直接将砾性土划分为非液化土类。但在2008年汶川地震中,成都平原地区发生了大规模的砾性土液化,为有记载以来全球规模最大,打破了天然沉积砾性土层不会发生液化的传统认识。目前学术界上对砾性土液化发生条件和影响因素的认识并不统一,甚至出现了同一学者在不同时期得出截然不同结论的情况,而埋藏条件、土性参数等因素对砾性土液化的影响是砾性土液化问题研究的基础性工作。本文以汶川地震现场勘查资料为基础,研究成都平原地区砾性土层埋藏条件对液化的影响,利用FLAC3D软件进行砾性土层液化问题模拟和分析,主要内容为:1.剖析了成都平原地区液化砾性土层的埋藏条件,包括地下水位、埋深、上覆粘土层厚度、可排水层厚度等,提出了成都平原地区砾性土层剪切波速与超重型动力触探击数关系的数学模型。2.选取了FLAC3D软件中本构模型以及合适的地震动输入,以此软件定性复现了汶川地震中四个典型(绵竹市汉旺镇武都村、绵竹市拱星镇祥柳村、郫县团结镇石堤庙村、都江堰市瑞康花园)砾性土液化与非液化场地的地震响应,结果与实际一致。3.建立了砾性土层概化模型,利用FLAC3D软件计算了近500种工况,初步分析了峰值加速度、土性参数(相对密度、渗透系数)、埋藏条件(上覆粘土层厚度、可排水层厚度)对砾性土层液化的影响。
[Abstract]:Before the Wenchuan earthquake in 2008, there are few reports on the liquefaction of gravel soil both at home and abroad. The problem of gravel soil liquefaction has not attracted the attention of the academia and the engineering community. It is generally considered that the permeability of gravel soil is good. The excess pore pressure in the earthquake is easily dissipated and the gravel soil is divided into non liquefied soil directly. But in the Wenchuan earthquake in 2008, it was formed. A large scale of gravel soil liquefaction has occurred in the plain area, which has been the largest in the world since recorded, breaking the traditional understanding that the natural gravel soil layer will not be liquefied. At present, the understanding of the conditions and influencing factors of the liquefaction of gravel soil is not uniform in the academic circle. In this paper, the influence of the burial condition of gravel soil layer on the liquefaction of gravel soil layer in the Chengdu plain area is studied based on the data of Wenchuan earthquake field, and the FLAC3D software is used to carry out the model of the liquefaction of gravel soil layer. The main contents are as follows: 1. the buried conditions of the liquefied gravel soil layer in Chengdu plain are analyzed, including the groundwater level, depth, the thickness of the overlying clay layer, the thickness of the drainage layer and so on. The mathematical model of the relation between the shear wave velocity of the gravel soil layer in the Chengdu plain and the number of super heavy-duty dynamic penetration is put forward, and.2. is selected to select the constitutive model in the software. The model and appropriate ground motion input are used to determine the seismic response of four typical Wenchuan earthquake (Mianzhu City, Hanwang Town, Wudu village in Hanwang Town, Mianzhu City, Xiang Liu village, shinetu village in Pixian and Rui Kang Garden in Dujiangyan city), and the seismic response of gravel soil liquefaction and non liquefaction sites in Wenchuan earthquake. By using FLAC3D software, nearly 500 kinds of working conditions were calculated, and the effects of peak acceleration, soil parameters (relative density, permeability coefficient), burial conditions (overlying clay layer thickness, sewerage thickness) on the liquefaction of gravel soil layer were preliminarily analyzed.
【学位授予单位】：中国地震局工程力学研究所
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU435

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