灌溉区黄土干湿循环劣化后蠕变特性及其促滑机理研究

Areas with landslides induced by irrigation have experienced the most frequent and serious geological disasters in the Loess Plateau region, causing huge losses to human lives and property and restricting the development of local economy and society to some extent. Especially, the groundwater level fluctuation resulted from irrigation in loess area causes the loess in the groundwater level fluctuation zone to suffer from periodic dry and wet cycles. Therefore, the creep characteristics of loess become more complicated under the condition that the physical and mechanical properties of loess experience change, and thus initiates landslides in this area. Based on creep mechanical tests after degradation of loess in irrigated areas under dry-wet (DW) cycles, this proposal intends to reveal the creep properties and the aging evolution law of strength parameter using an integrated approach of laboratory test and theoretical analysis. On this basis, the proposer attempts to establish a three-dimensional creep constitutive model describing the degradation factors of loess under DW cycles, and develop associated numerical simulation software package for applications. Furthermore, the proposed creep model would be verified by using the on-site monitoring data and numerical simulation method. The proposer will further seek the slide-causing mechanism of creep after degradation of loess in irrigated areas under DW cycles and provide innovative ideas on the prediction of landslide instability time in the future. The research findings will provide fundamental basis for understanding the long-term stability of landslide in irrigated areas with loess.

灌溉诱发滑坡地区是黄土高原地质灾害最为频繁和严重的地段之一，给当地群众生活和财产造成巨大损失，在一定程度上制约了当地的国民经济和社会的发展。灌溉区黄土受灌溉引起的地下水位波动，导致地下水位波动带的黄土遭受周期性的干湿循环，其物理力学性质发生了劣化，黄土的蠕变变形加剧，促进了滑坡的形成。本项目计划以灌溉区黄土干湿循环劣化后的蠕变力学试验为基础，采用室内试验与理论分析相结合的方法，揭示其蠕变特性和强度参数时效演化规律；依此，尝试建立描述黄土干湿循环劣化因素的三维蠕变本构模型，并在数值模拟软件中做二次开发，再利用现场监测数据和数值模拟方法对提出的蠕变模型进行验证，进而探寻灌溉区黄土干湿循环劣化后的蠕变促滑机理，为下一步开展滑坡失稳时间预测提供提供一种新的思路，研究成果将为黄土灌溉区滑坡的长期稳定性分析与防治提供试验积累和理论依据。

灌溉诱发滑坡地区是黄土高原地质灾害最为频繁和严重的地段之一，给当地群众生活和财产造成巨大损失，在一定程度上制约了当地的国民经济和社会的发展。本项目以灌溉区黄土干湿循环劣化后的蠕变力学试验为基础，采用室内试验与理论分析相结合的方法，取得了以下研究成果和发现：(1)获得了不同干湿循环后黄土的应力-应变-时间全过程曲线，获取了不同干湿循环次数下原状黄土的时间-应变规律、干湿循环次数与稳定应变值关系规律、黄土长期强度与干湿循环次数规律、不同干湿循环蠕变试验后黄土样品的宏观形貌特征和微观结构规律，揭示了干湿循环作用后黄土剪切力学特性的宏观、细观、微观多尺度劣化规律；(2)基于室内试验成果，根据损伤力学和蠕变力学理论，考虑黄土所遭受的干湿循环，在经典的Burgers?元件组合模型基础引入室内试验成果与所揭示的蠕变特性和强度参数时效演化规律，进而建立了一种描述黄土干湿循环劣化因素的蠕变模型，并推导其三维方程式表达式；(3)构建了典型黄土滑坡的数值模型，利用现场监测数据和数值模拟方法对提出的蠕变模型进行验证，通过数值模拟手段阐明蠕变效应和干湿循环条件联合作用下灌溉区黄土滑坡的运动特征，根据黄土干湿循环作用下黄土室内试验成果，结合野外调研，确定了灌溉区黄土滑坡蠕变致灾的关键因素，进而揭示灌溉区黄土的蠕变致灾促滑机理。本项目研究成果为黄土高原滑坡的长期稳定性分析与防治提供了试验积累和理论依据，具有重要的科学意义和实用价值。