软土层毛竹管桩排-土钉墙复合支护结构承载机理及设计方法研究

With the sustained development of urbanization construction in China, a large number of high-rise buildings between 15 floors and 35 floors were built whose foundations construction were usually supported with shallow excavation in soft soil layers. With the advantages of high tensile strength and relatively stable short-term strength, the bamboo can meet the requirements of temporary support for building excavation. Therefore, this project would be researched the mechanical properties of shallow excavation support in soft soil layer with bamboo tube pile row and soil nailing wall through site investigation, large scale model tests, centrifugal model tests and optical fiber sensing technology. The load transfer mechanism would be studied emphatically between bamboo tube pile row and bamboo tube used for soil nailing wall in the process of shallow excavation or support in soft soil to reveal deformation failure mode of composite retaining structure, and so that the composite design would be optimized bamboo tube pile row and soil nailing wall used bamboo rod. On this basis, the mechanical model would be established for composite retaining structure through bamboo tube pile row and soil nailing wall during shallow excavation in soft soil, and then its design methods will be put forward in engineering practice of shallow excavation support in soft soil to replace the traditional supporting mode used of high energy consuming and high emission both concrete and rebar during shallow excavation in soft soil layer. The research achievements will have important guiding significance for engineering design of shallow excavation in soft soil layer for bamboo rich areas in China and then produce significant benefits both in economic and social devlopments.

随着我国城镇化建设的继续推进，15-35层的高层建筑大量兴建，这类高层建筑的基础在软土层施工时大都采用浅基坑支护。毛竹具有抗拉强度高、短期强度相对稳定，符合建筑基坑工程支护临时性的要求。为此，本项目拟通过现场调查、室内大比例尺模型试验和离心模型试验及光纤传感技术，探索软土层毛竹管桩排复合土钉墙共同支护浅基坑的力学特性；着重研究在软土层浅基坑开挖与支护过程中毛竹管桩排与毛竹竿土钉墙的荷载传递机理，揭示复合支护结构在其施工过程中的变形破坏模式，以便优化毛竹管桩排与毛竹竿土钉墙的组合设计。在此基础上，建立软土层浅基坑毛竹管桩排复合土钉墙支护结构的力学计算模型，进而提出其在软土层浅基坑支护工程应用中的设计方法，以便替代在软土层浅基坑工程中由高能耗高排放的混凝土和钢筋组成的传统支护方式。该研究成果对我国盛产毛竹地区软土层浅基坑支护工程设计具有重要指导意义，并将产生显著的经济效益和社会效益。

随着我国城镇化的继续推进，20至40层的高层住宅建筑大量出现，这类高层建筑的基础在软土层施工时大都采用浅基坑支护。毛竹具有杭拉强度高，短期强度相对稳定，符合建筑基坑支护临时性的要求。为此，本项目通过了多地现场调查、室内大比例尺模型实验与数值仿真技术。首先，通过调查与研究我国盛产毛竹地区的资源状况，主要针对盛产毛竹地区毛竹资源分布特点，以毛竹管材为研究对象，开展毛竹力学特性和破坏特性的研究，测定其抗压强度、抗弯强度、抗弯弹性模量等静态力学性质、研究立地条件、竹龄、含水率和竹材部位等因素对其力学性能的影响变化规律，并构建了毛竹管材的静态力学模型。其次，针对软土地基高层住宅建筑浅基坑工程支护的受力特点，制定了分组试验方案，分单排与双排毛竹微型桩分别与毛竹土钉墙组合构成复合支护体系,进行大比例模型试验，分析了毛竹微型排桩桩周土剪切性状、变形性状、桩身抗湿滑性状以及毛竹土钉墙锚固作用及其发挥深度等问题，进一步深入研究毛竹微型桩排-土-土钉三者的受力特性及其共同支护作用机理。同时，进行了有限元分析，对室内缩尺寸模型试验建立了竹桩-土钉支护基坑的有限元模型，通过分析步的设定模拟了基坑分步开挖工况，围绕土体变形、桩身应变、弯矩、土钉轴力，分析竹桩-土钉支护结构的受力特性。着重研究了在软土层浅基坑开挖过程中毛竹管微型桩与毛竹管土钉墙荷载传递特性，揭示了软土层浅基坑破坏全过程的作用机理、破坏模式等，建立了软土层毛竹管微型桩排-竹篾-毛竹管土钉墙体系协同支护浅基坑的力学计算模型，提出了软土层浅基坑齿状排桩毛竹管微型复合土钉墙支护体系的设计理论。该项目目前产出期刊论文16篇，会议论文2篇，其中SCI论文2篇，EI论文4篇，培养毕业硕士3名，在读博士1名，部分研究成果纳入2019年湖北省科技进步二等奖（本人排名第一）。该研究成果对我国盛产毛竹地区的软土层浅基坑支护工程设计具有重要指导意义。