海口某深基坑支护数值模拟及土体本构模型研究

发布时间：2018-05-03 02:00

本文选题：基坑开挖 + 支护结构　；参考：《海南大学》2014年硕士论文

【摘要】：在基坑开挖工程中,基坑变形对基坑自身以及周围环境都有非常重要的意义,如何准确预测基坑在开挖过程中的变形是基坑工程中的重点和难点,目前数值分析是解决这一问题的有效方法。岩土本构模型既是岩土塑性力学的核心,也是数值模拟的基石。数值模拟的核心是本构模型和模型参数的选取,本文主要围绕常用的部分岩土本构模型的适用范围以及参数的选取等方面进行了相关研究。本文选取MC模型、MCC模型、HS模型和HSS模型,通过常规室内土工试验和三轴试验确定所取原状土的本构模型参数,结合基坑工程的勘察报告建立了一套与这四种本构模型相适应的参数选取方案,得到了相关土层的本构模型参数。利用Plaxis有限元程序对基坑工程进行数值模拟,将四种本构模型得到的数值模拟结果与实测结果对比分析得到以下结论： (1)土的弹性模量E可取5Es甚至更大；修正剑桥模型的参数兄和κ,可根据勘察报告提供的塑性指数Ip按推导出的公式计算；固结模量Eoed可取为Es,割线模量E50可取为2Eoed,卸载再加载模量Eur可取为5E50;小应变参数G0可取为2Eur,数值模拟结果受G0影响较大,且G0值越大数值模拟结果越接近实测结果,γ0.7波动范围较小,可取为2E-04； (2)MCC模型、HS模型和HSS模型模拟结果显示地表沉降表现为凹槽型,符合工程实际经验；围护桩变形表现为腹部向基坑内突出呈抛物线形,最大侧移发生在基坑开挖面附近。 (3)总体模拟效果最理想的是HSS模型,其次是HS模型和MCC模型,MC模型模拟效果不太理想。建议在基坑工程的有限元分析中应优先选用能够反映土体剪切硬化、压缩硬化、能够区分加荷和卸荷的刚度差异以及土体小应变特性的本构模型。建议海口地区采用HSS模型对基坑工程进行数值分析。 (4)对参数的选取进行优化,采用优化后的HSS模型参数得到的围护桩变形曲线与实测结果更为接近,变化趋势和数值都更接近实测结果。HSS模型的参数优化可适当加大刚度参数和参考剪切模量的取值。
[Abstract]:In the excavation of foundation pit, the deformation of foundation pit is very important to the foundation pit itself and the surrounding environment. How to accurately predict the deformation of foundation pit in the excavation process is the key and difficult point in the foundation pit engineering. At present, numerical analysis is an effective method to solve this problem. Geotechnical constitutive model is not only the core of geotechnical plastic mechanics, but also the cornerstone of numerical simulation. The core of numerical simulation is the selection of constitutive model and model parameters. This paper mainly focuses on the scope of application of some commonly used geotechnical constitutive models and the selection of parameters. In this paper, we select MC model, MCC model, HS model and HSS model, and determine the constitutive model parameters of the undisturbed soil by conventional indoor geotechnical test and triaxial test. Based on the investigation report of foundation pit engineering, a set of parameter selection schemes suitable for these four constitutive models are established, and the constitutive model parameters of related soil layers are obtained. The numerical simulation of foundation pit engineering is carried out by using Plaxis finite element program. The numerical simulation results obtained by the four constitutive models are compared with the measured results and the following conclusions are obtained: (1) the elastic modulus E of the soil should be even greater than that of the 5Es, and the modified parameters of the Cambridge model, brother and 魏, can be calculated according to the derived formula according to the plastic index Ip provided by the survey report. The consolidation modulus (Eoed), the Secant modulus (E50), the unloading modulus (Eur) and the small strain parameter (G0) can be considered as Ess, 2Eoed50, 5E50 and 5E50, respectively, and the numerical simulation results are greatly affected by G0. The larger the value of G _ 0 is, the closer the numerical simulation results are to the measured results, the smaller the fluctuation range of 纬 _ (0.7) is, the desirable is 2E-04. The simulation results of HS model and HSS model show that the surface subsidence is groove type, which is in line with the practical engineering experience, and the deformation of the retaining pile is that the abdominals protrude into the foundation pit with parabola shape, and the maximum lateral displacement occurs near the excavation surface of the foundation pit. (3) the best simulation effect is HSS model, followed by HS model and MCC model. It is suggested that in the finite element analysis of foundation pit engineering, the constitutive model which can reflect the shear hardening, compression hardening, stiffness difference between loading and unloading and the characteristics of small strain of soil should be selected first. It is suggested that HSS model be used for numerical analysis of foundation pit engineering in Haikou area. 4) the parameters are optimized, and the deformation curve of the retaining pile obtained by the optimized parameters of the HSS model is closer to the measured results. The variation trend and value are closer to the measured results. The parameter optimization of the HSS model can increase the stiffness parameter and the reference shear modulus.
【学位授予单位】：海南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU473.2;TU470

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