开挖卸荷作用下黄土边坡多尺度损伤与变形演化机制研究

The frequent occurrence of catastrophic landslides caused by the excavation executed in a loess slope is one of the commonly encountered engineering problems in the Loess Plateau. This has been a major factor restricting the sustainable development of the local economy. Excavation induced loess landslides are characterized by their occurrence in hysteresis and abruptness; therefore, it is very difficult to forecast such type of landslide. For a systematic and in-depth study of this issue, the failure mechanism and deformation features of loess landslides, triggered by excavation, are chosen as the research theme of this project. Triaxial test, micrographics processing technology and centrifuge model test are chosen as the primary research methods in this study. The goals of this research are to investigate the macroscale failure and mechanical response, microstructural deformation and damage mechanism of soils in different influence areas of excavation, to reveal the internal relation between the time-dependent deformation and the interaction of excavation and loess slope geological structure, and to establish a rational constitutive model of loess to reflecting the different unloading stress paths due to excavation. On the basis of this analysis method, numerical simulations under complex conditions are planned to carry out by applying the proposed model, the time-varying model for multi-factor deformation of loess slope under different excavation conditions is hereby established. A thorough investigation of the aforementioned geological disasters is of great significance not only in developing the multi-scale deformation and failure theory of loess landslides, but also can provide a scientific basis for the prevention and control of loess landslides triggered by excavation.

黄土高原工程活动导致滑坡灾害频繁发生，其中工程开挖诱发黄土滑坡已成为该地区广泛分布的一类地质灾害，严重制约着地区社会经济的可持续发展。开挖卸荷型黄土滑坡常表现出较强的突发性与滞后性的特点，增加了对滑坡预报的难度。本项目拟围绕开挖与黄土滑坡这一工程界与学术界关注的焦点与热点问题，以揭示开挖卸荷作用下黄土边坡变形及滑移灾变机理为研究主旨，通过室内三轴试验、微观图像处理技术与离心模型试验等手段展开，研究开挖扰动边坡不同影响区土体的宏观力学响应与细微观变形损伤机制，揭示开挖卸荷与黄土边坡地质结构效应互馈作用下边坡时效变形特征及其内在联系，建立可反映不同开挖影响区应力路径的黄土卸荷本构模型。在此基础上开展复杂工况数值计算，构建卸荷型黄土边坡变形多因素时变模型。项目研究成果将有助于深化黄土滑坡多尺度变形破坏理论，为卸荷型黄土滑坡灾害防控提供科学依据。

黄土高原大规模工程建设为区域发展带来了前所未有的空间和机遇，同时引起的边坡灾变隐患与安全风险问题也日益剧烈。围绕工程开挖诱发黄土滑坡灾变与防控的系统性研究中面临着大量的科学难题，项目以卸荷型黄土滑坡为研究对象，基于现场调查、室内应力路径试验、微观图像分析及离心模型试验等手段，对卸荷作用下边坡土体宏观力学响应及细微观变形破坏、边坡应力重分布与时变演化特征、不同开挖影响区卸荷路径的黄土本构关系等问题开展研究，取得了若干有意义的研究成果。首先基于现场调查成果提取卸荷型黄土滑坡分布与区划特征数据，从宏观尺度阐明该类滑坡工程诱发机制与致灾过程，厘清其空间分布规律和成灾模式。在此基础上，针对滑坡原型不同开挖影响区卸荷特征，通过室内三轴试验探究了不同含水率、应力路径及卸荷速率对黄土力学性状与卸荷变形的影响，从宏观力学响应角度揭示了卸荷型黄土滑坡的激发机制；开展卸荷路径变化条件下黄土细微观结构试验，查明了黄土微结构损伤劣化及其量化参数的变化过程。其次，开展黄土边坡开挖模拟的离心模型试验，分析了不同开挖角度和地层结构对坡体应力重分布及位移场变化的影响，揭示了开挖边坡的时效变形规律、卸荷分区响应及滑动带生成机理。随后，基于上述应力路径试验与离心模型试验结果，分析考虑不同开挖影响区卸荷路径的黄土本构关系及其适用性，构建了能合理反映不同卸荷路径的黄土弹塑性本构模型。最后，分析卸荷作用下黄土时效变形与粘弹塑性特征，初步建立了卸荷型黄土边坡变形多因素时变模型。本项目的研究对深化工程地质营力与黄土边坡灾变的互馈机理与调控理论具有重要意义，为黄土地区工程性滑坡的防控减灾提供理论基础和科学依据。