【作者】 吴钰骅；

【导师】 朱向荣；

【作者基本信息】 浙江大学 ， 岩土工程， 2004， 硕士

【摘要】 本文选择基坑工程中广泛采用的传统弹性地基梁法进行三维有限元分析，探讨了内撑式围护结构的总体性状，并对环梁进行稳定分析。研究表明，传统弹性地基梁法中的地基反力系数无法考虑软土的流变性以及塑性的影响，取值过于经验性。这对围护结构变形、内力预测结果的影响很大，直接影响了围护结构方案的安全性和经济性。 在前人研究的基础上，本文采用对土体抗剪强度分类的方法研究了软土的流变性，提出了重塑土粘滞系数的计算方法，重点分析了常规试验中部分参数由于流变而引起的试验误差。在对软土流变研究的基础上，采用抗剪强度折减的方法在基坑工程中考虑流变的影响。 针对当前国内外弹性地基梁法存在的缺陷，基于对软土流变性的研究，采取了剪应力判断弹塑性状态，以改进和完善基坑工程弹性地基梁法，推导了弹性状态下地基反力系数的近似解，提出了采用剪应力组合判断土弹簧弹塑性状态的方法，编制了相应的弹塑性共同变形法分析程序DPFBM1.0(Double Plastic Foundation Beam Method(Version 1.0))，并采用该程序分析了压缩模量、粘聚力、内摩擦角等参数变化对基坑工程的影响。 为了检验DPFBM1.0程序的准确性，本文采用该程序对工程实例进行了分析。分析结果表明：采用固结快剪强度指标的分析结果与基坑工程刚开挖完时的实测值相近：采用三轴固结不排水强度指标的分析结果与基坑暴露时间较短时(24天左右)的实测值相近。更多还原

【Abstract】 Based on elastic foundation beam method, three-dimensional finite element analysis is used for foundation excavation. However, analysis results are influenced by limitations of elastic foundation beam method, rheological effects, plastic behavior of soft soil can’t be considered. Moreover, the coefficients of subgrade reaction are often determined by empirical analysis, which influences the security and economy of foundation engineering.To discuss the rheological effects of soft soil, shear strength is divided for rheological analysis. Viscosity coefficient of remolding soil is used to modify partial parameters of routine soil mechanic tests. So the shear strength caused by rheological effects can be considered.Based on shear stress-strain relation of soft soil, an approximate solution to the coefficient of subgrade reaction in elastic stage is proposed. To discuss the plastic behavior, the shear stress is divided to simplify the judgment of elastic and plastic stage. Then the judging method is proposed, and the proposed method can consider the stress history and viscosity shear strength of soft soil.In this paper, a FEM program DPFBM1.0 (Double Plastic Foundation Beam Method (Version 1.0)) is established. With this program, the influence of some parameters on foundation excavation is fully studied, the parameters include: compression modulus, cohesive strength, angle of internal ficiction, effective angle of internal friction, the embedded length of the wall and building load.To verify the program, a foundation excavation case is analyzed respectively by DPFBM1.0 and elastic foundation beam method. Some conclusions are obtained: consolidated quick shear test is appropriate for excavation completion stage, and triaxial consolidated undrained test is for short-term excavation.更多还原