三维边坡的失稳与加固机理研究

Slope instability is typical geological disaster in hydraulic engineering, traffic engineering and civil engineering. It is also a hot research topic in the field of engineering geology and geotechnical engineering. Instability of the soil slopes shows obvious three-dimensional behavior because of the influence of the surrounding soil, and the reinforcements in soil slope will enhance such space effect. Due to the limitations of mathematical modeling and mechanical analysis, the two-dimensional analysis is still a common method in slope stability analysis. The instability mechanism and limit analysis method of three-dimensional soil slope is studied based on the model tests and analytical analysis. Three-dimensional slope model tests with loading method and centrifuge modeling method are carried out to investigate the failure mechanism of instability and the sliding surface characteristics. The influence rules of different soil parameters and scale of slope are analyzed. A new three-dimensional limit analysis method for the stability of soil slopes is presented based on the mathematical model of sliding surface obtained from model tests. The limit analysis method is then improved by considering the stiffness and strength of reinforcements in the three dimensional slope. The interaction behavior between the soil slope and reinforcements is discussed by model tests of reinforced slope and limit analysis. The results of this research can explain the instability and reinforcement mechanism of the three-dimensional slope. The proposed model test methods and equipment can be applied to other studies. The three-dimensional limit analysis method and the stability evaluation method of the reinforced slops can be used in the design and mitigation control for disaster.?

边坡失稳是水利水电工程、交通工程和城市建设中常见的工程地质灾害，也是工程地质和岩土工程领域的研究热点。土质边坡失稳因周围土体约束的空间效应而呈现明显的三维特征，加固体的存在将进一步强化三维效应。由于数学模拟与力学分析方面的局限，二维分析方法仍是边坡稳定分析中的常用手段。本项目针对三维土质边坡的稳定性问题，采用模型试验和解析分析相结合的方法开展系统研究，探索土坡三维失稳的机理及其极限分析方法。通过三维边坡失稳的压载试验和离心试验确定其破坏机制和滑动面特征，分析土体参数的影响规律；基于所得滑动面，研究三维土质边坡稳定性的极限分析方法，进而提出考虑加固体刚度与强度作用的三维分析理论，结合模型试验探讨土坡与加固体共同作用机理。研究成果对于阐明三维边坡失稳与加固机制具有重要意义，提出的试验方法和设备可应用于相关研究，三维极限分析和加固评估方法的建立为边坡稳定的分析设计与减灾控制提供科学依据。

边坡稳定问题一直是岩土工程领域研究的热点，普遍存在于水利水电工程、公路工程、铁路工程、矿山工程、城市建设与改造等工程建设中。边坡稳定性分析逐渐从二维分析向更符合实际情况的三维分析迈进。坡顶荷载是堆土填方、基坑工程、铁路边坡、公路边坡、坡顶建设活动等稳定性分析中不可忽略的因素。因此，准确的分析和评价三维边坡在顶部荷载下的失稳机制和滑动特征，以满足工程边坡和开挖工程稳定性分析的精确要求，是岩土工程研究中的重要课题之一。本项目以细砂边坡为研究对象，采用模型试验和数值模拟的分析方法，深入研究坡顶荷载下细砂边坡失稳机制和滑动特征，讨论坡面几何形态和坡体初始含水率对边坡失稳规律的影响。（1）设计了坡顶荷载下三维边坡失稳模型试验系统和测量系统，借助模型系统对三维边坡进行模型试验；（2）模型边坡在坡顶荷载下触发失稳破坏，坡顶位移计、坡内土压力盒分别记录坡顶位移和坡内土压力的变化。利用数码相机和白砂层模型分别获取边坡外部破坏过程、形态和滑动面特征，并且考虑坡面形态（平、凸、凹）和坡体初始含水率对边坡破坏的影响，深入认识边坡破坏机制；（3）对比模型试验结果，分析坡面形态和坡体初始含水率对边坡破坏过程、破坏模式、破坏整体形态、滑动面特征、滑面深度、滑动范围、破坏难易程度等的影响；（4）采用SVOffice岩土工程数值分析软件，模拟边坡的稳定性和破坏形态，分析坡体初始含水率、坡顶荷载、坡面形态对稳定性和破坏形态的影响。土体含水率越高，抗剪强度越低，边坡更易触发失稳。坡顶荷载加重边坡的负担，边坡更容易破坏。相同坡高、坡角下，凹坡最稳定，平坡次之，凸坡最不稳定。