山区陡坡路基微型桩-加筋土挡墙的工作机理研究

With the rapid development of economy in China, the construction of mountain highway increases day by day. The MSE (Mechanically Stabilized Earth) wall is a suitable way for subgrade in steep terrain of the mountainous areas. However, there exist some problems in the MSE wall constructed in steep terrain which must be solved quickly, for example, the deformation of the MSE wall is relatively large, its global stability is relatively inadequate on steep slope and the requirement for impact resistance of road barrier is relatively high. In view of these construction problems of mountain highway in steep terrain in China, a new style of earth retaining structure called “Micropile-MSE wall” for subgrade is put forward in this project, which aims to reduce the deformation of the MSE wall and improve its global stability as well as impact resistance of road barrier simultaneously. First, model tests will be conducted to verify the effectiveness of Micropile-MSE wall, and the test results can also provide basic validation for the corresponding numerical simulation. Then the global stability, anti-seismic performance, impact resistance of road barrier of the Micropile-MSE wall as well as the corresponding reinforcement mechanisms etc. will be studied through numerical simulation, and the working mechanism of the components of Micropile-MSE wall will be researched through theoretical analysis. The research results can enrich the study on the deformation analysis theory of earth retaining structure in steep terrain, and it is helpful in making full use of the steep terrain suitably so as to provide some guidance for the increasing highway construction in mountainous area in China.

随着我国经济建设的迅速发展，山区公路的建设需求日益增大。加筋土挡墙是山区陡坡地带路基填筑的合适手段。然而，陡坡地带常规的公路加筋土挡墙存在变形较大、整体稳定性不足、对公路护栏安全性能要求较高等难题，亟待解决。本项目针对我国山区陡坡路基的建设难题，提出“微型桩-加筋土挡墙”的新型路基支挡结构，以期一举多得地实现减小公路加筋土挡墙变形、增强整体稳定性和护栏防撞性能的多重加固目的。首先，通过模型试验，初步检验所提出的微型桩-加筋土挡墙的有效性，同时也为数值模拟的准确性提供基本验证；而后，充分利用数值计算手段，对微型桩-加筋土挡墙的整体稳定性、抗震性能、公路护栏的防撞性能和相应的加固机制等展开研究，并通过理论分析，研究微型桩-加筋土挡墙中各部件的工作机理。研究结果将丰富山区陡坡路基支挡结构的变形分析理论，有助于因地制宜地充分开发和利用这类陡坡地段，为我国日益增加的山区公路建设提供指导。

针对山区陡坡路基的设计、施工难点和可能遭受的破坏，在系统地总结了以往边坡及支挡结构加固措施的基础上，开发了“微型桩-加筋土挡墙”系统，采用技术开发、模型试验和理论分析等研究手段，对系统抗变形能力、公路护栏的抗冲击能力以及相应的加固机理等展开系统研究。主要工作内容及结论如下：.（1）通过对比水平场地和斜坡加筋土挡墙的应力变形特点，提出斜坡加筋土挡墙存在墙身变形、基底压力、面板侧移和侧向土压力等过大的问题，这些问题主要是由其基本破坏模式——回填土区域整体沿着边坡的下滑所引起的，且回填土强度的降低或墙高的增加都会显著地增大其变形。这些问题的发现，为山区公路挡土墙加固措施开发的必要性和合理性提供了依据。.（2）开发了一种适合于山区特点的“微型桩-加筋土挡墙”系统，即采用竖直和倾斜的一对微型桩从路面穿过回填土区域并锚固进地基，同时在桩顶处浇筑地基梁，通过连接构件将公路护栏与地基梁及微型桩相连，形成一个自上而下的三角形加固体系，即可达到提高挡土墙局部稳定性、整体稳定性和护栏抗冲击性能的多重目的。.（3）开展了斜坡加筋土挡墙的静载缩尺模型试验研究，结果表明，“微型桩-加筋土挡墙”采用竖直和倾斜的一对微型桩形成的三角形加固体系，在控制附加荷载引起的面板侧向位移、挡土墙顶部沉降、桩身弯矩、基底压力和侧向土压力等方面都具有明显的效果，显示了其优越性，同时也为数值模拟研究提供了参考。.（4）开展了加固前后的斜坡加筋土挡墙的护栏冲击动力响应的对比研究。与加固前相比，碰撞冲击作用下的护栏位移可减小约90%，面板最大侧向位移可降低82.1% ~ 94.3%。