多排沉埋－全长组合桩加固大型基覆式滑坡力学机制及计算理论研究

Multi-row embedded stabilizing piles is a novel combined retaining structure with pile top of the first fore row revealed on the surface and the rest rows embedded in the slope. Compared with traditional multi-row stabilizing piles, the structure can be of reasonable mechanical characteristics and low cost, which is very suitable for large-scale accumulate landslide control. However, mechanism and analytical theory of the novel structure can still not be established, which restricts its extensive application to a great extent. The project aims at this question so as to set up general scientific theories for large-scale slope reinforcement with such multi-row embedded stabilizing piles. The main research contents involve in laws of stress transmission of rock or soil mass between adjacent pile rows, and the effect of embedded depth of pile top and row spacing on the laws; the influence of pile spacing, contact surfaces between pile and potential slide mass or bedrock, and strain softening effect of the slope materials on the interaction mechanism between multi-row embedded stabilizing piles and the large-scale landslide, and the results of distribution pattern of lateral pressure on every pile and stress transmission characteristics of rock or soil mass between adjacent pile rows affected by these factors; theoretical formula of embedded depth of pile top, rational relationship between the embedded depth and row and pile spacing, reasonable combination of embedded depth of every pile top and range of row and pile spacing, i.e. an approach to rational layout of the structure, as well as theoretical analysis model of piles considering elastoplastic characteristics of slide mass, stable layer and stabilizing piles. A comprehensive and efficient analytical theory of multi-row embedded stabilizing piles is expected to be established. The research is of good prospect of extensive application and important significance in theory and practice.

多排沉埋－全长组合桩是一种后面各排沉埋式、最前一排全长式的新型组合式多排抗滑桩结构，具有比传统的多排全长式抗滑桩受力更合理、经济性更好的优点，适于大型基覆式滑坡治理。但其抗滑力学机制和计算理论还未合理建立，极大限制了其广泛使用。本项目针对此问题开展研究，旨在为新型多排沉埋桩加固大型斜坡提供共性科学理论基础。主要内容包括：揭示考虑坡体材料应变软化效应、桩体不同深度与坡体接触面特性等因素的多排沉埋桩与坡体相互作用机制，确定多排沉埋桩排间岩土体的空间传力特征，及其受桩顶沉埋深度、排间距（主滑断面内）与桩间距的影响规律；建立桩顶埋深的理论计算公式，提出沉埋－全长组合式多排桩合理桩顶埋深组合及其与桩、排间距的关系，确立结构合理选型的方法；充分考虑滑体、滑床及桩的弹塑性特性，建立多排桩内力及变形理论计算模型。最终形成一套实用有效的多排沉埋-全长组合桩计算理论。本研究应用前景广泛，有重要理论与实际意义。

多排沉埋－全长组合桩是一种后面各排沉埋式、最前一排全长式的新型组合式多排抗滑桩结构，具有比传统的多排全长式抗滑桩受力更合理、经济性更好的优点，适于大型基覆式滑坡治理。但其抗滑力学机制和计算理论还未合理建立，极大限制了其广泛使用。本项目针对此问题开展研究，旨在为新型多排沉埋桩加固大型斜坡提供共性科学理论基础。通过对西南、西北地区典型大型基覆式滑坡的现场调查，确定了大型基覆式滑坡的典型滑动模式，将其归纳为3类，即：陡倾折线滑面滑动模式、直线型滑面滑动模式、缓倾折线型滑动模式；依托典型实例，利用改制的直剪仪，获得了坡体材料的直剪全过程曲线和应变软化特征，并确定了抗剪强度参数的软化规律，进而可用于确定抗滑桩上滑坡推力变化规律；采用弹塑性数值模拟方法，建立了反映多排沉埋-全长组合式抗滑桩与坡体相互作用的精细力学分析模型，并通过室内模型试验与现场试验，考虑滑带土应变软化、排间距、桩顶埋深等多因素影响，进一步揭示了多排桩与坡体的相互作用机制；基于变形能的概念，构建了全新的边坡稳定系数定义及边坡稳定性分析方法，新定义表示为滑面上各微段抗剪强度平方和与剪应力平方和之比的平方根，避免了用沿滑面极限抗滑力合力除以下滑力合力的概念缺陷；提出了对竖向条间界面破坏状态修正的改进传递系数法，弥补了传统的传递系数法对相邻滑面倾角差异较大时的理论局限性；鉴于滑体在沉埋桩顶可能发生越顶破坏的模式，提出了基于极限平衡理论与极限分析考虑坡体稳定性的桩顶埋深与桩体内力分析方法，实现了桩顶埋深与加固坡体的设计安全系数的联系；提出了考虑后排桩设置位置与滑面抗滑作用相互关系的多排抗滑桩的合理组合型式，形成了多排沉埋-全长组合式抗滑桩加固大型基覆式滑坡的成套计算理论。本项目研究成果应用前景广泛，特别适于大型滑坡治理工程，有重要理论与实际意义。