多节旋挖挤扩DX桩基承载特性及失效机制试验研究

Thanks to some remarkable advantages, such as high bearing capacity, small settlements and pile length reduction and raw material saving,rotary extruded-expanded cast-in-place concrete pile (hereinafter referred to as DX pile) with expanded plates, a new kind of pile with varied cross-section recently developed,has been widely applied in pile foundation of civil engineering, expressway bridges engineering, high speed railway bridge engineering,port engineering,even large LNG project.Since test reports and engineering applications show the superiority and development potential of this type of pile, study of bearing characteristics and design method of DX pile has undoubtedly become a new hot spot for pile foundation engineers and researchers in recent years. As the existence of multiple plates have greatly changed load transfer law and characteristics of settlements of traditional pile with uniform section for its pile-soil interaction complexity, exploration of DX pile load transfer science law remains very insufficient.The study for this application will carry a series of model tests, site tests on a single model pile to identify the load transfer characteristic,deformation and failure mechanism of DX pile, and try to establish DX pile bearing capacity design method, which fills a gap of this research field. The research results will not only promote development of pile foundation design theory ,but provide an important solution of practical engineering problems, especially with the rapid development of super-long pile foundation in high speed railway engineering, highway engineering currently.It is expected that the study for this application will have important effectiveness for both academic and pratice.

多节旋挖挤扩DX 桩基（简称DX桩）是近年兴起的一种异型多承盘桩基形式，因其可显著提高桩基承载力、减少沉降、降低桩长及节约原材料，在高速公路、铁路、港口码头甚至大型LNG储油罐的桩基工程得到广泛应用。试验报告和工程应用均表明该桩型的优越性与发展潜力,因此对该桩的竖向承载性能与其设计方法研究，近年来已成为桩基工程研究人员的新热点。但因多承力盘的存在改变了传统等截面桩的荷载传递规律和沉降特性，桩土之间相互作用较为复杂，研究人员对DX桩荷载传递方式等科学规律的认识还很不充分。本课题拟通过一系列模型试验、理论分析与数值模拟等多种手段，对DX桩的荷载传递机理及承载特性进行研究，掌握承力盘、桩身与土体的相互作用规律，从而建立DX桩竖向承载力设计方法。研究成果将大大发展桩基设计理论。尤其当前我国高速铁路、公路工程中超长桩基越来越多，本课题研究成果及应用既具有重要的理论意义，又具有广泛的工程实用价值。

多节旋挖挤扩DX 桩基（简称DX桩）是近年兴起的一种异型多承盘桩基形式，因其可显著提高桩基承载力、减少沉降、降低桩长及节约原材料，在高速公路、铁路、港口码头甚至大型LNG储油罐的桩基工程得到广泛应用，收到了良好的经济效益和社会效益。试验报告和工程应用均表明该桩型的优越性与发展潜力, 因此对该桩的竖向承载性能与其设计方法研究，近年来已成为桩基工程研究人员的新热点。但囿于多承力盘的存在，桩的荷载传递规律和沉降特性与传统等截面桩相比，发生了明显的改变，多段侧阻力和多层端阻力共同承载的复杂荷载传递过程，使桩土之间的相互作用非常复杂，研究人员对DX桩荷载传递特性、承载机理及破坏模式等科学规律的认识还很不充分。因此，提高对DX桩荷载传递特性、承载机理及破坏模式等科学规律的认识，迫在眉睫。本课题结合工程现场试验、模型试验、理论推导及数值分析等手段，对DX摩擦桩及嵌岩桩的竖向荷载传递机理及承载特性进行系统研究，建立了DX 桩极限承载力、桩顶位移、桩身轴力等变化规律，确定了DX嵌岩桩竖向承载力的主要影响因素，明确了DX桩承力盘、桩身与土体的相互作用规律，系统揭示了DX桩的竖向承载机理，提出了DX桩的竖向承载力设计方法。研究成果大大丰富了桩基设计理论。尤其当前我国高速铁路、公路工程中超长桩基越来越多，本课题研究成果及应用具有重要的理论意义及工程实用价值。