【作者】 郭超；

【导师】 闫澍旺；

【作者基本信息】 天津大学 ， 岩土工程， 2011， 博士

【摘要】 低强度桩复合地基主要通过桩体的置换作用来提高地基的承载力,控制地基沉降,增强地基稳定性。低强度桩包括水泥搅拌桩、水泥砂浆桩、高压旋喷桩、CFG桩等强度比钢筋混凝土桩低的多的素混凝土类桩。由于低强度桩的强度和成桩工艺的多样化及土体的离散性,导致了低强度桩复合地基复杂的工程特性。为了更深刻的理解低强度桩复合地基的工程特性,本文采用理论计算、数值模拟分析、原位观测等相结合的方法,综合分析了复合地基中的桩体、加筋垫层、土体、上部荷载在复合地基中的相互作用,对整个复合地基的影响。分析过程,从低强度桩复合地基变形模式出发,建立了一组低强度桩复合地基变形及稳定性应力-应变协调方程。方程推导过程中,考虑了桩-土-垫层之间的相互作用,得出了桩土应力比和等沉面深度的解析解,并进一步得出了桩和桩间土体的应力分布规律及压缩变形量、桩体上刺入垫层、下刺入下卧土层的刺入量。在此基础上,通过与复合地基下卧土层的压缩变形量求和,最终推导出了低强度桩复合地基的总沉降计算公式。进一步采用弹性地基梁理论分析了群桩中基桩的稳定性和挠曲变形特性。根据上述复合地基的应力-应变协调方程中得出的桩间土的受力状态,采用摩尔-库伦理论分析桩间土的绕桩破坏。通过低强度桩复合地基的应力-应变协调方程图表化,应用到工程实际设计中。利用通用有限元软件对低强度桩复合地基进行弹塑性分析。引入素混凝土弥散开裂模型的弹塑性本构关系,得出低强度桩复合地基的沉降及破坏规律。通过路堤试验段的原位测试,对低强度桩复合地基加固的路堤进行包括沉降、测斜在内的全方位观测,证明了理论计算结果和数值分析结果的合理性。更多还原

【Abstract】 Low strength pile composite foundation increases the foundation bearing capcity, decreases the foundation settlement, and enhances the foundation stability by the piles replancement. Low strength pile is the plain concrete pile, including cement mixing pile; cement morta pile; high-pressure rotary jet grouting pile; CFG pile etc., which strength is lower then reinforced concrete pile. The low strength piles foundation display the complicated engineering character, for the variety of strength and construction technology.This paper uses theoretical calculation method; numerical simulation analysis method; in-situ obversion method, integrated analysis the low strength pile foundation piles, reinforced cushion, soil among piles, upper load effect in the whole low composite foundation system,during the different forced periods and different position.Based on the low strength piles composite foundation deformation model, a group of deformation and stability calculating equations on the low strength piles composite foundation is put forward. During the equations derivation, the interaction between the piles-soil-cushion is considered, and the stress-strain compatible equations are constructed. At the same time, the piles-soil stress ratio and the equal-settlement-surface analytical solution are also received. Further more, the piles and their surround soil stress distributing regulation, compress deformation, and the up-stick-deformation of the cushion and the lower-stick-deformation of the soil are all obtained. Through the summary of composite layer settlement and the piles surround soil compress deformation, the whole settlement of the composite foundation is deduced. The piles stability and flexibility are analyzed by the elastic foundation beam theory. The soil among the piles, winding pile failure is analysised by the Mohr-coulomb model on the upon stress condition. The stress-strain compatible equations are used in the engineering by diagrammatized. The foundation settlement and sability regulation are researched through the elastic-plastic finite element method, which includes plain concrete smeared cracking model. Theoretical calculation and numerical simulation result are proved by the embankment test section.更多还原