气候-渗流耦合作用下高海拔大梯度斜坡岩体失稳机理

The mountain environment in high altitude large gradient region, where landslides and debris flows occur frequently, facilitates the development of high-speed long-runout landslides. Focusing on typical rock slopes in the eastern fringe of the Tibetan Plateau, evolutionary history and disaster characteristics of steep rock slope in the high altitude cold region were studied in detail. The surface hydrology process and the transformation of water and heat between the atmosphere and the ground were investigated. The underground seepage was predicted based on the results of field survey. The role of thermal stress on the mechanical behavior weakening of rock mass was studied through the temperature cycling test. The statistical relationship between the climate and rock mechanical properties was established. The transfer mechanism of water and heat in the joint rock mass was analyzed based on the results of field monitoring and laboratory tests. The coupling mathematics model of moisture-thermal-stress of jointed rock mass was established and the propagation process of rock fractures was simulated. The mechanical mathematical model, which can simulate the stability evaluation process of a steep rock slope in the high altitude cold region, was obtained. The quantitative assessment of the rock slope stability at any time was given. This study can provide a foundation for regional sustainable development and prevention of landslide and debris flows in high altitude cold regions.

高海拔大梯度山地环境是滑坡和泥石流灾害的多发地区，为高速远程滑坡的发育提供便利的地形条件。本项目以青藏高原东缘典型岩质边坡为研究对象，对高海拔大梯度斜坡岩体力学特性演化规律及灾变条件进行详细的研究。通过现场调查，了解研究区的地表水文过程及大气-岩土体水热耦合的传输过程和传输机制，对地下水渗流量进行模拟和预测。通过室内岩体气候模型试验，分析温度应力在岩体力学性质弱化过程中的作用，建立起定量的统计学关系模型。在现场监测成果分析和室内试验的基础上，分析节理岩体在环境温度变化过程中的水热迁移机制，建立高海拔冰缘区水-热-力耦合的岩体节理扩展数学模型，实现对岩体节理扩展过程和力学行为的动态模拟。在此基础上，建立反映高海拔大梯度岩质边坡稳定性演化全过程的数学模型，实现边坡稳定性演化的实时定量评价，为区域可持续发展和灾害风险防范提供决策支持。

在对高寒岩质边坡现场调查的基础上，采集现场岩石试样，进行室内岩石冻融循环试验，对不同岩性岩石的冻融劣化机理及边坡失稳机理进行研究。首先通过砂岩长时间的冻融循环试验研究，获得不同循环次数砂岩的饱和质量、干质量、孔隙率以及纵波波速的变化过程。发现在冻融循环的过程中，砂岩的孔隙率逐渐增大，力学参数随着冻融循环次数的增加而逐渐减小，力学参数的退化服从分段衰减特征；其次通过含随机裂隙花岗岩冻融损伤试验，分析试样的纵波波速、质量、裂隙率等参数变化的原因，得出冻融循环试样的物理性质变化规律，探究其损伤速率的大小和快慢，探究影响损伤速率和损伤程度的原因。通过试样在不同循环周期的核磁共振试验，研究其孔隙分布及变化规律，分析岩石的微观损伤特性；对冻融后的试样进行力学试验，探究其力学性质变化规律，根据试样在破坏后展现的破坏形态，把破坏模式总结为劈裂破坏、拉剪破坏、单剪破坏、双剪破坏、X型破坏和不规则破坏，随着冻融循环的进行破坏形态和破坏后的破碎程度都在发生变化，是定性分析损伤程度的方法之一；对影响裂隙岩体冻融损伤速率的冻胀力进行了推导，并得到纵波波速、孔隙率两个指标衡量损伤状态的方法，减小了单一参数作为衡量指标的不稳定性。通过对单一预制裂隙岩样冻融过程中的裂隙变形、扩展和裂隙冰、岩相互作用规律研究，分析岩体中裂隙扩展规律和岩体深部冻融破裂机理；研究了表层固话技术进行寒区边坡防护的可行性，对不同类型固化剂坡表防护层的力学特性、抗渗透性和抗冲刷性进行了研究；建立了考虑岩体初始损伤、冻融损伤以及孔隙压密变形的岩石软化损伤本构模型，通过与室内试验对比研究，证明该模型能够很好的反映冻融岩体在受荷条件下力学性质的变化规律，模型中参数获取容易，适用性强，可以用于边坡岩体冻融弱化情况下的边坡稳定性分析。