沟谷堆积体与微型抗滑桩群协同工作的宏细观机理及设计理论

A wide range of landslides are easily induced due to the development of high and steep slopes in the Yalong River basin, the complex geological and topographic conditions and loose structure of talus slopes in valley. Meanwhile, the researches on the treatment technique and design theory of talus slopes in the complex environment are obviously inadequate at present. Based on the typical talus slopes encountered in the hydropower projects which are located in the middle and downstream of Yalong River, micromechanical constitutive mode of coarse soil-structural contact is established through super large-scale triaxial tests and large-scale direct shear tests, then the new contact algorithm for the interaction between pile-soil interface and the DEM-FEM coupling approach are developed to investigate the macro-meso mechanism of collaborative working between anti-slide micropiles and deposit slopes. Subsequently, the new numerical method is verified by using the geo-centrifuge modeling tests with the combination of the advanced fiber bragg grating (FBG) and the particle image velocimetry (PIV) technology; then a detailed parametric study is conducted to reveal the load transfer characteristics due to the soil arching among adjacent anti-sliding mircopiles and micropile groups, further to put forward the distribution mode of later earth pressure acting on the micropile. Based on above work, the micropile group patterns and the corresponding simplified design methods are proposed for different scales (shallow, middle and deep) talus slope in valley considering the characteristics of the actual topography and the external load conditions. And the establishment of the design of anti-sliding micropile groups can provide technical support to the development of hydropower projects, the treatment of talus slopes in valley and the disaster prevention and mitigation in the southwest mountainous areas with the fragile geologic environment.

雅砻江流域高陡边坡发育，地质地形条件复杂，沟谷堆积体结构松散，极易诱发大范围滑坡，而目前针对复杂环境下沟谷堆积体治理技术和设计计算理论的研究明显不足。以雅砻江中下游水电工程高陡边坡群典型沟谷堆积体为依托，采用超大型三轴和大型直剪试验建立粗粒土-结构接触的细观本构模型，开发考虑桩-土界面相互作用的新型接触算法和DEM-FEM耦合数值方法，探索微型抗滑桩群与沟谷堆积体协同工作的宏细观机理，利用先进的光纤光栅和PIV联合监测技术的离心试验验证数值方法；通过深入地变动参数比较研究，揭示微型抗滑桩-桩群-相邻桩群间的荷载传递机理和土拱效应机制，提出桩侧土压力分布模式。在此基础上，针对真实地形地貌特征和外荷载条件，提出不同规模（浅、中、深层）堆积体边坡的微型桩群组合模式及简化设计计算方法，从而建立抗滑微型桩群的设计理论，为地质环境脆弱西南山区水电工程开发、沟谷堆积体边坡治理和防灾减灾提供技术支持。

本项目在国家西部水电大开发、川藏铁路建设和山区自然灾害防灾减灾救灾的战略背景下，主要针对雅砻江流域高陡边坡群复杂地质地形条件地带沟谷堆积体边坡（滑坡）的稳定性评估及微型桩群加固处治技术所开展的一项具有科学理论创新和实际应用价值的研究。.针对堆积体边坡稳定性快速评价问题，开展了现有数值计算软件的高效算法优化与改进，运用Python编程语言进行二次开发，通过优化强度折减算法、初始应力场载入和计算时步上限显著提升了软件计算效率，发展了一种适用于三维复杂堆积体边坡稳定性快速评价的高效数值计算方法；结合颗粒介质力学特性，开展了堆积体边坡滑坡运动过程室内模型试验和离散元数值模拟，构建颗粒粒度特征、地形条件指标与滑坡运动参数之间的定量化关系，提出一种滑坡堆积体形态预测经验公式；在微型抗滑桩加固堆积体边坡所涉及的颗粒土与结构接触作用的细观本构模型上取得了一定进展，结合有限元FEM和离散元DEM计算理论，发展了一种能够从宏细观尺度上描述桩土相互作用的耦合数值方法和程序；采用离心机模型试验技术手段，验证了所发展数值方法的有效性与准确性，并进一步探究微型抗滑桩群与堆积体边坡的协同变形机制及桩土相互作用规律；为服务工程实践，基于建筑信息模型BIM平台开发了复杂三维斜坡地形和微型抗滑桩群数值建模模块，发展微型抗滑桩群加固堆积体边坡的快速优化设计方法。项目研究取得的成果可为堆积体边坡稳定性评价、微型抗滑桩群加固边坡优化设计和堆积体滑坡应急处置对策的制定提供科学依据和技术方法。