真三轴湿载作用下湿陷性黄土渐进破坏力学行为研究

Water sensitivity caused by the destructuring of structured under the condition of shearing, compression and moisturing is the core of mechanical behavior of collapsed loess. The funtion including disturbance of excavation, loading and increased moisture content can lead to amounts of engineering disasters such as landslides, subsidence, slip of surrounding rock and ground fissure. As for structural damage of loess and progressive failure of soil under the condition of complex stress pathes and increased moisture content. Two structural parameters is also as to ligament of structural damage analysis under coupling of loading and increased moisture. The isotropic compression, shearing and moistening of the true triaxial tests are adopted. It is systematically analysed that the structure evolution laws of compression-damage, shearing-damage, compression-moisturing-damnage, shearing-moisturing-damnage of loess under the conditions of compression, compression-shearing, compression-shearing-moisturing. The relationships between structural damage and deformation, strength are studied. The double-structural-parameter and double-yield surface constitutive model reflecting evolution of structural damage under coupling of compression shear and moisture is formulated. Research provides the theoretical basis of improving design of collapsible loess tunnel and evaluational method of foundation collapsibility, and it is an important theoretical and practical significance.

非饱和黄土具有显著的水敏性与结构性。在开挖扰动、加载以及增湿作用下会引起黄土工程的塌方、沉陷、滑移、地裂等灾害。针对湿与载共同作用下黄土的结构损伤与土体的渐进破坏性状，从结构性参数出发，并将其作为湿与载耦合作用下土结构损伤分析的纽带，假定增湿与增荷两种作用引起塑性应变相同时的结构损伤程度是相当的，通过真三轴应力条件下等向压缩、剪切以及增湿试验，系统地分析“压”、“压-剪”、“压-剪-湿”作用下黄土结构的压损、剪损、压湿损伤与剪湿损伤的变化规律，研究结构损伤与屈服、变形、强度之间的关系，建立“压-剪-湿”耦合作用下结构损伤演变的湿陷性黄土弹塑性本构模型。研究成果为完善湿陷性黄土工程的设计和地基湿陷变形评价方法提供理论基础，具有重要的理论与实际意义。

非饱和黄土具有显著的水敏性与结构性。在开挖扰动、加载以及增湿作用下可能引起黄土工程的塌方、沉陷、滑移、地裂等工程问题。基于构度指标和应力比结构性参数，提出了一种综合的结构性指标，能够反映初始结构状态和复杂应力条件下增湿路径对黄土结构状态的影响。研究了构度指标与基本物理量之间的关系。开展真三轴应力条件下的湿陷试验和剪切试验，研究了湿陷性黄土的压损、剪损、压湿损伤以及剪湿损伤演化规律，并以塑性应变相同时的结构损伤程度是相当这一根本认识为纽带，综合考虑4种损伤的联系，建立了黄土的弹塑性本构关系。将该本构关系嵌入FLAC3D数值软件，开展了在湿陷条件下隧道围岩变形及衬砌结构稳定性的三维数值研究，探讨了地裂缝活动作用下黄土覆盖层破裂机制及其对隧道衬砌结构的影响。依托隧道地基的现场浸水试坑试验，研究了黄土隧道围岩湿陷引起的衬砌结构破坏的力学机制与防治措施。黄土隧道围岩湿陷引起衬砌结构破坏的力学机制与防治措施已应用于宝鸡至兰州高铁湿陷性黄土隧道工程。考虑地裂缝活动作用和黄土结构性变化的黄土覆盖层破裂机制及其对隧道衬砌结构影响研究已应用于西安地裂缝区域地铁隧道工程。