黄土高填方在高压、浸水和强夯作用下诱发地质灾害机理及其演化模式研究

Selecting the filling reclamation project in Yan'an as its study subject which characterizes collapsible loess and considering the impacts of high pressure, dynamic compaction loading and water on high fill engineering, this research aims to establish both the dynamic and static constitutive models of fill soil by examining its engineering mechanics characteristics under the condition of soaking, high pressure and dynamic compaction loading. The three dimensional numerical models of loess before and after its consolidation, collapsibility and collapse are built by using scanning electron microscope. In addition, the change in mineral composition before and after the test of loess is analyzed using energy depressive spectroscopy, electron probe and ICP to explore the mechanism of loess' collapsibility, deformation and collapse under various pressures. Based on the results of the above experiment and considering the size of particle composition, the amount of cement, the pore structure as well as the granulometric composition of loess, this study creates the three dimensional numerical models of undisturbed soil and compacted soil by using the discrete element program developed by our research team. Then dynamic and static loads are applied to the three-dimensional numerical models to reproduce the process of deformation, collapse and vibration subsidence of loess in order to find out factors which affect the collapsibility and seismic subsidence of loess. Finally, using the method of FLAC3D to establish three dimensional geological models of the typical fill area to reveal the stress & strain distribution and failure characteristics under the influence of dynamic and static load. As a result, this study proposes the evolution pattern and mechanism of the possible geological hazards which may occur in the filling reclamation project in the new district of Yan'an initiated by the external load. The findings of this research will provide scientific theories for the filling reclamation project in the study area.

以黄土地区延安填沟造地项目为研究区，抓住“高压、强夯和水”对填方工程的影响，研究填方土在浸水、高压和强夯荷载下的工程力学特性差异，建立相应工况下黄土的本构模型。结合氩离子抛光电镜扫描分别构建固结、湿陷和振陷前后黄土的三维结构；利用能谱分析、电子探针和ICP等测试手段，分析黄土试验前后矿物成分和可溶盐的变化；探索高压、浸水和强夯作用下黄土的变形、湿陷和振陷机理。基于黄土颗粒成分和大小、胶结物多少、孔隙结构以及粒度成分等，利用团队开发的离散元程序构建原状土和压实土的三维模型，分别施加动、静荷载进行数值模拟，重现土的变形、湿陷和振陷过程；摸清影响黄土湿陷和振陷的影响因素；最后，利用FLAC3D软件建立填沟造地前后三维地质力学模型，模拟不同填筑高度、水和强夯动力荷载作用下填方体应力应变和破坏特征，提出黄土高填方在外部荷载作用下可能引发的地质灾害的机理及其演化模式，为该区的移山填沟工程提供科学理论

考虑到黄土丘陵沟壑区环境地质条件的复杂性以及黄土力学的特殊性，本研究通过室内试验、现场试验与数值模拟相结合，宏观研究和微观研究相结合，多学科综合研究的基础上，展开了原状土和压实土在高压、浸水和强夯荷载作用下的变形与强度及其工程特性差异研究，分别建立了原状土和压实土的动、静及湿陷本构模型，确定其模型参数；探索了黄土在不同压力、不同含水率和不同强夯振动荷载作用下的变形、湿陷和振陷特性及其机理，重现了黄土的变形、湿陷和振陷过程；探明了陕西延安新区移山填沟工程中的高填方工程在外部荷载作用下可能引发的地质灾害及其机理，完善了延安新区建设中黄土和压实土的工程特性数据库，为黄土丘陵沟壑区的工程建设中“高填”设计、施工提供了技术保障和理论依据。