基于多功能CPTU的深厚软土刚性桩水平承载机理分析与设计方法研究

The lateral loads become control loads during the design of rigid piles section as development of port engineering and ocean engineering. However, the theoretical research of laterally loaded rigid pile has far behind in engineering application. Based on the working characteristics similarity of CPTU and laterally loaded rigid pile, with the physical modeling test, numerical simulation and theoretical deduction the following studies will be accomplished. The influence law of pile design parameters and soil properties effect on pile-soil interaction will be analyzed and a lateral load transfer model will be proposed. The lateral load transfer mechanism of pile-soil interaction using CPTU test data will be revealed by the correlation of CPTU penetration and mechanical properties of laterally loaded pile. Then, the lateral load transfer model by CPTU test result will be put forward. The failure probability model will be proposed as well as sensitive factor analyzing based on evaluating of CPTU data spatial variability using random field theory. Finally a reliability design method of lateral capacity for laterally loaded rigid pile based on CPTU test will be established. It has important theoretical value and practical guiding significance to improve the design ability of laterally loaded rigid pile in the deep soft soil.

随着港口工程、海洋工程等建设事业的发展，水平荷载在刚性桩断面设计中成为控制荷载，但其理论研究却滞后于工程应用。本项目基于多功能孔压静力触探（CPTU）技术与刚性桩水平承载性状的相关性，采用室内模型试验、数值模拟和理论推演相结合的方法，分析深厚软土中刚性桩设计参数和土性指标对桩-土相互作用的影响规律，建立刚性桩水平荷载传递模型；阐明多功能CPTU测试指标与水平承载桩力学性能的相关关系，揭示基于CPTU的刚性桩水平荷载传递机理，建立相应荷载传递模型；分析CPTU测试参数空间变异性随机场，建立刚性桩水平承载力失效概率模型，研究失效敏感因素；总结建立基于多功能CPTU的刚性桩水平承载力可靠度设计计算方法。研究成果对提高我国深厚软土中水平受荷桩的设计和应用水平具有重要的理论价值和实践指导意义。

随着港口工程、海洋工程等建设事业的发展，水平荷载在刚性桩断面设计中成为控制荷载，但其理论研究却滞后于工程应用。本项目基于多功能孔压静力触探（CPTU）技术与刚性桩水平承载性状的相关性，采用室内试验、数值模拟和理论推演相结合的方法，研究了深厚软土中刚性桩水平承载特性及机理。. 深厚软土刚性桩贯入分析表明，桩侧挤土效应沿贯入深度逐渐增强，桩端处最强，桩端以下迅速衰减；桩端以下影响深度为8倍桩径，桩侧土径向位移临界深度为10倍桩径；贯入阻力和土中水平向应力分别随着土体内摩擦角、剪胀角、粘聚力和静止土压力系数的增加而增大；贯入阻力约在土层界面以上1倍桩径处达到峰值，土层界面对贯入阻力、桩侧土水平向应力和位移的影响范围为界面上5倍桩径至界面下6倍桩径。. 总结分析世界范围内不同土质条件下单桩竖向承载力试验成果基础上，将基于CPTU的软土不排水强度公式引入Ruiter和Beringen提出的刚性桩承载力估算方法（简称欧洲法）中，建立了考虑超固结比（OCR）、水平应力（σh）和长径比（L/D）的深厚海陆交互相软土中刚性桩竖向承载力非线性计算方法。. 通过现场试验和室内离心机试验，研究了深厚软土中不同桩端开口形式、桩体截面形状和桩侧土排水条件下刚性桩水平承载特性及桩土相互作用机理。结果表明，单桩水平承载力随桩侧土锥尖阻力的增大而增大；闭口桩的水平承载力大于开口桩；桩土响应处于线弹性阶段时，荷载-位移曲线与桩端类型及截面形状无关；沉桩引起的超孔压完全消散后，刚性桩水平承载力得到提高；桩身材料、桩端开口形式和桩入土深度相同时，H型桩的水平承载力最大，而圆截面桩最小。综合分析试验结果表明: 归一化桩顶水平荷载 － 桩顶水平位移曲线符 合指数函数关系。