【作者】 王洪亮；

【导师】 宋二祥；

【作者基本信息】 清华大学 ， 土木工程， 2013， 硕士

【摘要】 紧邻既有建筑的基坑开挖过程中对变形控制非常严格，同时坑周土体宽度有限使得很多支护方案在这里都不适用，因此对这类基坑支护进行研究具有重要意义。本文在前人已有研究成果基础之上，通过理论分析与数值模拟相结合的研究方法，针对这一类基坑支护设计时遇到的几个问题进行了系统的研究。论文前半部主要研究各种不同情况下的土压力计算方法，随后在此基础上对紧邻既有建筑基坑的支护设计进行了探讨。具体的研究工作包括以下几个方面：（1）通过理论分析和数值模拟对现行规范中有关坑边局部荷载引起支护结构上土压力的规定进行了较深入的讨论，分析了土体参数c和φ对附加土压力弹塑性解的影响，发现其与静止土压力系数的正比例关系；针对土体分层情况，利用有限元法分析了附加土压力的分布形式；针对基坑周边建筑物荷载的作用，分析了基础埋深对附加土压力的影响。利用正态分布曲线拟合了下卧土层的附加压力，并在此基础上推出了计算地表超载引起挡土结构上附加土压力的简化公式。（2）基坑挡土结构与既有建筑基础间形成有限土体，此时土压力的计算不能采用通常情况下的朗肯理论或库伦理论。通过对挡土墙与既有建筑基础间的有限土体进行完整的受力分析，考虑了既有建筑基础与有限土体间的法向及切向相互作用力，建立了求解有限土体主动土压力的计算公式，并进行了适当的简化。通过与有限元结果对比证实本文给出的简化公式形式较为简捷，精度较高。在应用公式的过程中要考虑位移的因素以及中主应力对强度参数的影响，本章对这些问题也进行了讨论。（3）分析了水对土压力的影响，包括渗流对土压力的影响，以及非饱和土与饱和土强度差异引起土压力的不同。（4）由于锚杆的设置受到限制，常使护坡结构的横向支护不足，寻找其他措施以减小变形成为这类基坑支护需关注的重点。通过三维数值模拟各种不同的支护方案，发现了一些减小变形的方法：上部土钉墙支护并适当放坡可有效减小护坡桩的悬臂长度；双排桩对这类基坑支护有一定的优势；充分利用周边建筑原来的支护系统等等。对桩径的选取、放坡的深度也进行了讨论。提出一种新型的支护方案，通过限制桩顶弯曲达到减小变形的目的，经有限元验证其效果不错。更多还原

【Abstract】 The excavation adjacent to existing buildings has very strict requirements ondeformation control. At the same time, it makes a lot of support system not applicablehere that the width of soil outside the foundation is narrow. Based on the existingresearch results, through theoretical analyses and numerical simulations, severalproblems on the support design for this kind of foundation pit are studied systemically.In the first several chapters the calculation methods of soil pressure in differentconditions are discussed, and then the support design is analyzed. Research workincludes the followings:(1)Through theoretical analysis and numerical simulation, it makes furtherdiscussion about the soil pressure on retaining structures in the current code ofrelevant local load, and the effect of soil parameters c and φ on additional earthpressure of elastoplastic solution. It is found that additional pressure and staticearth pressure coefficients has proportional relationship. Distribution of earthpressure of layered soil is analyzed by the finite element method; the influenceof the depth on additional earth pressure is also analyzed. By using the normaldistribution curve fitting of the additional pressure of underlying stratum, thecalculation formulas of additional earth pressure caused by additional surchargeis introduced.(2)Between retaining wall and the existing building foundation the finitesoil is formed, where soil pressure calculation by using Rankin theory orColumn theory cannot be used directly. In this paper complete mechanicalanalysis of the limited soil is conducted, which has considered the lateral andtangential forces between the limited soil and the wall. Then the equations forcalculating the active earth pressure are established, and a simplified formulafor this case is presented finally. It is verified by the finite element results thatthe simplified formula derived in this paper has relatively simple form and highprecision. In the process of application of formula, the effect of displacementfactors and intermediate principal stress should be taken into account, so theseproblems are also discussed in this chapter. (3)The effect of water on the earth pressure is analyzed, includinginfluence of seepage on earth pressure, and different earth pressure caused byshear strength of unsaturated soils.(4)It makes the supporting pile cantilever structure that the anchor cannotbe constructed, so looking for other measures to reduce the deformationbecome the focus of attention. Through the three-dimensional numericalsimulation of different supporting scheme, some methods decreasing thedeformation are found: the upper soil nailing wall can effectively reducecantilever length of the pile; double-row piles have a certain advantage insupport design of this kind of foundation; making full use of the originalsupporting system of the surrounding building etc. At the same time, theselection of pile diameter, slope depth were also studied. A new support schemeis proposed, by limiting the torsion of the pile, it can reduce the deformationeffectively.更多还原