松散堆积体滑坡与抗滑桩相互作用细观机理

Soil-rock mixtures are inhomogeneous and loose materials with a certain percentage of rock blocks. This kind of materials is widely distributed in the nature, for example, as components of landslides. Under the consideration of inhomogeneity and discontinuity, further research should be undertaken to identify the key outstanding issues at a meso-scale level for the mechanical behavior of soil-rock mixtures and the interaction between anti-sliding piles and geomaterials. This proposal thus aims to provide a solid foundation for the design of anti-sliding piles for landslide mitigation after well understanding the mechanical behavior of geomaterials. In the present study, a typical landslide is selected to be a case study in loose quaternary deposits, and its mechanism would be analyzed for the engineering geomechanics model after the detailed geological survey. In order to well understand the mechanical behavior of soil-rock mixtures in reality, databases will be constructed for the shapes of rock blocks, and the detailed description carried out for their geometry in two/three dimensions. Using the digital image processing and numerical simulation techniques, the mechanical behavior can be then explained after lots of numerical simulation tests by Particle Flow Code. Meanwhile,a small-scale experiment is expected to be carried out in sites for the interaction between the geomaterials and anti-sliding piles, completely different from the traditional method. Following the experiment and numerical simulations by combination of PFC and FLAC, environment factors are analyzed with regard to the development of arching effect. Especially, this work finally seeks to exactly know how the structure of rock blocks affects the development and evolution of arching in the design of anti-sliding piles for slides with soil-rock mixtures. The expected outcome is original for the mechanism of the interaction between slope and pile for the stabilization in loose quaternary deposits at a meso-scale level.

考虑到土石混合体非均质和非连续性，研究土石混合体真实力学特性且从细观力学角度探讨松散堆积体抗滑桩拱效应的存在条件、形成和发展演化过程，可以为抗滑桩设计与优化提供重要的理论基础，服务于滑坡灾害防灾减灾。本项目拟选取典型松散堆积体滑坡抗滑桩治理工程为重点研究对象，结合详细的野外地质调查和监测资料，科学分析重点堆积层滑坡体变形破坏机制，构建其工程地质力学模型；在系统分析土石混合体结构特征的基础上，建立和完善土石混合体中块石形貌特征信息库，实现块石颗粒几何形态空间表述；借助现代影像处理和数值模拟技术，在室内和现场模型实验的基础上，开展土石混合体真实力学特性研究；利用三维离散-连续耦合数值分析技术，重点剖析松散堆积体滑坡抗滑桩细观尺度下工作特性，分析块石结构特征和空间分布规律对拱存在条件和形态特征的影响，系统研究抗滑桩拱效应形成和发展演化过程，揭示抗滑桩与松散堆积体滑坡相互作用细观力学机理。

考虑到土石混合体非均质和非连续性，研究土石混合体真实力学特性且从细观力学角度探讨松散堆积体抗滑桩拱效应的存在条件、形成和发展演化过程，可以为抗滑桩设计与优化提供重要的理论基础，服务于滑坡灾害防灾减灾。本项目拟选取三峡库区典型松散堆积体滑坡抗滑桩治理工程为重点研究对象，分析了奉节生基包堆积层滑坡体变形破坏机制；在系统分析土石混合体结构特征的基础上，并结合岩土体散体材料介质特性的描述，建立和完善砂土颗粒、土石混合体中块石形貌特征信息库，实现了不同类型颗粒几何形态和空间表述；块石元局部应变系数为土石混合体代表单元中各介质元细观微应变与体积平均应变的桥联系数，与土石混合体的细观结构、初始围压直接相关。随着含石率的增大，土石混合体的抗剪强度也随之增大，块石元的结构支撑效应越明显。在散体材料宏细观参数之间的联系方面，材料的峰值抗压强度直接受控于颗粒的粘结强度和颗粒的摩擦系数，另外颗粒摩擦系数直接影响材料峰后力学特性。在室内试验和数值模拟散体材料和抗滑桩相互作用机理方面，采用离散元的方法对非连续、非均质介质的土拱效应进行深入的研究，从细观层面上分析土石混合体自身性质（含石率、块石分布、块石形态等）以及桩间距对桩后土拱形成、演化、破坏的力学机制；同时，我们发现：桩位显著影响桩固边坡的安全系数，桩充分发挥性能得到最大安全系数的最小嵌岩比为0.12。嵌岩比影响桩的加固性能，嵌岩比增大，桩的挠度显著减小，弯矩和剪切力也会随之减小，弯矩与剪切力的峰值位置略高于滑动面位置。对不同模式的模型检验表明，嵌岩桩长比大于临界值时，边坡安全系数、桩的挠度、弯矩和剪力处于稳态。随桩距减小，桩的性态类似于连续材料，土拱效应也更为明显。当桩间距增大时，各桩的承载区增大，其最大弯矩值和剪切力会增加，因此安全系数下降。以上研究结果系统研究了抗滑桩拱效应形成和发展演化过程，揭示了抗滑桩与松散堆积体滑坡相互作用宏细观力学机理。