板连式束筋微型抗滑桩群加固滑坡机制及计算理论研究

Combined anti-sliding micro-pile group is a light retaining structure with several micro-piles connected by a reinforced concrete plate at their top. The micro-pile is highly slender pile with 110-150mm diameter of hole in which one to three steel rods surrounded by cement grout are arranged. The structure can be constructed conveniently, quickly and safely, and be helpful to environmental protection, which is very suitable for moderate and small slope or landslide treatment. However, mechanism and analytical theory of the structure can still not be established, which restricts its extensive application to a great extent. The project aims at this question so as to establish general scientific theories for such structures that are combinations of slender anti-sliding micro-piles. The main research contents involve in interaction mechanism between every micro-pile and soil surrounding it inside a unit of the combined structure with normal and tangential mechanical characteristics of the interface considered, laws of stress transmission on the slope strike and slip direction of the soil between micro-piles inside a unit, distribution pattern of lateral pressure on every micro-piles inside a unit with slender pile group effect and strain softening effect considered simultaneously, and mechanical principle of the plate as well as reasonable types and analytical methods of the micro-pile group fit for various landslides or slopes. The research is of good prospect of extensive application and important significance in theory and practice.

板连式束筋微型抗滑桩群是指数根微型桩在顶部用钢筋混凝土板连接的轻型组合抗滑结构，微型桩为在直径110～150mm孔中用几根钢筋组成束筋作骨架再在其周围注入砂浆的长细比极大的细长桩体。具有施工灵活、安全快捷、低碳环保等优点，适于中小型滑坡及边坡治理。但其加固滑坡的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。本项目对此问题开展研究，旨在为类似的微小直径细长抗滑桩组合结构提供共性科学理论基础。主要内容包括：考虑单元微型桩群中各细长桩与周围岩土体接触面的力学性质，揭示二者间力学作用机制，含桩侧法向挤压和切向摩擦作用；确定单元微型桩群中桩间岩土体的空间应力传递和扩散规律，包括沿坡体走向和滑动方向；探讨同时考虑细长桩群桩效应和滑带土应变软化效应的桩侧坡体压力作用规律；确立顶板力学作用机制，建立适于不同滑坡特征的单元微型抗滑桩群合理结构型式及计算方法。本研究应用前景广泛，有重要理论与实践意义。

板连式束筋微型抗滑桩群是指数根微型桩在顶部用钢筋混凝土板连接的轻型组合抗滑结构，微型桩为在直径110-150mm孔中用几根钢筋组成束筋作骨架再在其周围注入砂浆的长细比极大的细长桩体。具有施工灵活、安全快捷、低碳环保等优点，适于中小型滑坡及边坡治理。但其加固滑坡的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了研究，旨在为类似的微小直径细长抗滑桩组合结构提供共性科学理论基础。通过对西南地区大量道路边坡的现场调查，获得了适宜微型桩加固的典型坡体结构特征，将其归纳为类均质土质边坡、堆积体－基岩式边坡和顺层岩质边坡共三大类；考虑桩土相互作用特征，进行了单元微型桩群的合理结构型式研究，建立了考虑桩群间距的空间刚架分析模型以分析结构；分析了单元微型桩群所受滑坡推力在平面内的二次分配，得出在矩形和三角形分布模式下，平面内各桩体受力分配系数拟合公式，影响因素敏感性分析结果表明分配系数受桩长的影响最为敏感，受桩间距、桩径和土体弹性模量等影响较弱；采用塑性极限分析方法，建立了单排桩加固土坡的极限分析模型，考虑了桩体两侧潜在滑面不连续的情况，推导了相关计算公式，可计算桩体所受坡体极限推力；揭示了顶板作用机制和单元微型桩群间土拱效应形成机制，通过数值方法分析了桩体几何及力学参数对土拱效应的影响规律，建立了估算单元微型桩群间距的方法；依托典型工程，利用自动伺服式直剪仪，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，进而用于确定微型桩群上滑坡推力变化规律；考虑滑带土软化特征，采用弹性地基约束的整体模型和极限分析模型，分别建立了单元微型桩群的分段和整体计算方法，并将微型桩群拓展到多级框架锚杆结构（后者为前者的倾角变换），形成适于平面、圆弧面、折线型滑面等滑坡的合理且操作简单的结构分析方法。本研究应用前景广泛，特别适于斜坡快速治理工程，有重要理论与实际意义。