【作者】 姜龙；

【导师】 王连俊；

【作者基本信息】 北京交通大学 ， 水文地质与工程地质， 2009， 博士

【摘要】 为提高运输效率,实现客货分离,对客运专线和高速铁路的建设势在必行。桩板复合地基是处理客运专线、高速铁路软土和松软土地基应用较多的一种方法,但相应的设计规范还不完善,而且缺乏具体的设计计算方法指导,同时对处理后沉降时效特性及施工周期的认识也不清楚,严重影响了其应用的科学性。基于此,本文以京沪高速铁路为依托,采用现场试验、理论分析和数值计算等手段,系统地研究了桩板复合地基沉降时效特性,分析了桩板复合地基各参数对其沉降时效特性影响的程度和规律,并对其主要影响因素进行了按沉降控制优化设计。主要研究内容和成果如下:对京沪高速铁路凤阳试验段桩板复合地基进行了现场试验研究,并对现场检测和监测试验结果进行了分析,主要包括对单桩及单桩复合地基载荷及变形、桩土荷载分担、地基表面沉降、地基分层沉降、孔隙水压力等的特性和规律分析。基于桩土罚函数接触,建立了Biot固结理论的三维流固耦合数值模型,并依据现场试验数据进行对比分析,验证了该模型能很好地模拟现场基本工况的沉降变形,在研究桩板复合地基沉降时效特性方面是可行的。通过三维数值模型试验,研究了路基荷载下褥垫层参数、桩体参数(桩长、桩径和桩问距)、土体参数(初始孔隙比、压缩性和渗透性)和填筑参数(填筑高度和填筑速率)等参数对桩板复合地基(端承桩和摩擦桩两种情况)的超孔隙水压力、桩土附加应力、地基表面沉降、地基深层沉降、加固区压缩量和下卧层压缩量的影响程度和变化规律。增加桩体长度、桩体直径、土体初始孔隙比、土体渗透性,减小褥垫层厚、桩体间距、土体压缩性,有利于超孔隙水压力消散,缩短固结沉降时间,其效果以增加土体渗透性最为显著。增加桩体长度、桩体直径,减小桩体间距、土体初始孔隙比、土体压缩性,有利于控制沉降变形,其效果以增加桩体长度最为显著。建立了桩板复合地基按沉降控制优化设计体系,研究了端承桩桩板复合地基沉降时效特性的主要影响因素为桩间距和堆载预压,并提出了疏密桩设计思想;而摩擦桩桩板复合地基沉降时效特性的主要影响因素为桩长和堆载预压,并给出了基于桩长和堆载预压参数的按沉降控制的摩擦桩桩板复合地基优化设计方案。更多还原

【Abstract】 To improve transport efficiency and achieve separation of passenger and freight, construction of special passenger line and high-speed railway is imperative. Pile-slab composite foundation is a method commonly used to treat soft soil and incompact soft soil foundation of special passenger line and high-speed railway. But relevant design standards are not perfect, and specific guidance to the design and calculation methods is still scarce, and at the same time exploration of settlement time property and construction cycle after treated is not clear, which seriously impacts on its scientific nature.Based on above analysis, this paper, via construction background of Beijing-Shanghai high-speed railway, is intended to systematically study the settlement time properties of pile-slab composite foundation and analyze regularity and extent of parameter effect of pile-slab foundation on settlement time property, and the main factors are by settlement-controlled optimum design. The main research work and accomplishment of the paper are generalized as follows:Field tests of pile-slab composite foundation in Fengyang section of Beijing-Shanghai high-speed railway have been done, and field detection and observation results have been analyzed mainly including single pile and composite foundation and its deformation, load bearing of pile and soil, surface settlement, layered settlement, pore water pressure.Based on the penalty function contact of pile and soil, 3-D liquid-solid coupled numerical models of Biot consolidation theory have been established, and it has been verified that the models can better simulate settlement deformation of the field basic working conditions and are feasible in the study of settlement time properties through analyzing and comparing with field detection results.Through 3-D numerical model experiment, regularity and extent of parameter effect of cushion, pile length, pile diameter and pile space, initial void ratio, compressibility and permeability, filling height and filling rate under loading on excess pore water pressure of pile-slab composite foundation(bottom bearing pile and friction pile), pile-soil additional stress, surface settlement, deep settlement, compression of the reinforced area and compression of the underlying layer, is studied.Increasing pile length, pile diameter, initial void ratio of soil and permeability of soil and reducing cushion thickness, pile space and compressibility of soil, is advantageous to dissipation of excess pore water pressure and shortening the consolidation time and the effect of increasing permeability of soil is most remarkable. Increasing pile length and pile diameter and reducing cushion thickness, pile space, initial void ratio of soil and compressibility of soil, is helpful for controlling the settlement deformation and the effect of increasing pile length is most remarkable.The system of settlement-controlled optimum design of pile-slab composite foundation is established, and the main factors for pile-slab composite foundation of bottom bearing pile are pile space and surcharge preloading, and design ideas of sparse-density pile are brought; the main factors for settlement time property of pile-slab composite foundation of friction pile are pile length and surcharge preloading, and the ideas of settlement-controlled optimum design are brought.更多还原