填海造陆地区深大基坑变形时空效应及其控制研究

发布时间：2018-01-09 02:05

本文关键词：填海造陆地区深大基坑变形时空效应及其控制研究　出处：《重庆大学》2015年博士论文　论文类型：学位论文

【摘要】：随着我国城市化进程快速的发展,不断扩张的城市建设与有限的土地资源之间的矛盾日益凸显,因此,填海造陆成为沿海城市增加土地资源储备、扩展城市空间的重要途径。如今伴随各种高层、超高层建筑的建设,各种超大、超深和复杂的基坑工程在填海造陆地区的场地上应运而生,然而,填海造陆层下卧深厚的海相沉积软土在基坑开挖过程中容易产生蠕变变形,使基坑支护结构及周围土体的变形具有明显的时空效应,为了基坑的安全施工,需要对时空变形进行严格地控制。填海造陆层下卧的海相沉积软土的蠕变力学特性是影响整个基坑时空变形的重要因素,鉴于此,论文基于前人对软土蠕变的研究,综合采用室内试验、理论分析、数值模拟等手段,对下卧海相沉积软土的蠕变力学特性和本构模型展开研究,并将研究成果应用到填海造陆地区深大基坑变形时空效应及其控制的工程实践中。论文的研究内容和成果如下:①对基坑海相沉积软土的基本物理性质和矿物成分进行系统的研究,揭示了高亲水矿物含量、高细粒含量和高粘粒含量是造成海相沉积软土非线性蠕变的重要原因。采用应力控制式三轴仪,对不同深度处的海相沉积软土展开相应围压下的固结不排水蠕变试验,获得该软土的蠕变特性认识。基于试验结果,重点分析海相沉积软土在低于屈服应力和高于屈服应力时各自的蠕变特性,以及蠕变特性随时间的变化规律,通过拟合得到孔隙水压随蠕变时间和应力水平的函数关系式。②分析基坑海相沉积软土的线性粘弹性蠕变和非线性粘塑性蠕变的规律,采用标准线性体描述粘弹性蠕变、标准线性体与经验公式相结合来描述粘塑性蠕变,建立以元件模型和经验模型为组合体的海相沉积软土的蠕变本构模型。采用基于经典拟牛顿BFGS算法的MATLAB程序,对软土蠕变本构模型的参数进行辨识,获得较高精度的模型参数,能够很好地描述不同深度处海相沉积软土的蠕变特性。③基于有限差分理论推导海相沉积软土应力场控制和渗透场控制的差分方程;利用Microsoft Visual C++6.0软件获得该软土蠕变本构模型的数值实现程序Szsoftsoilmodel.dll。根据该数值实现程序得到围压为100kPa、200kPa和250kPa时的蠕变数值计算结果,通过数值计算结果和蠕变试验结果的对比,验证了数值实现程序的正确性,为基坑海相沉积软土蠕变模型的工程应用奠定了基础。④根据实际起伏不定的地层建立深大基坑的三维模型,分别利用软土蠕变模型和Mohr-Coulomb模型对支护桩的水平位移进行数值计算。对比数值计算结果和现场监测数据,结果表明:考虑软土蠕变模型的桩身水平位移比Mohr-Coulomb模型的计算结果更加符合实际的桩身水平位移,验证软土蠕变模型的数值实现程序用于基坑变形数值分析的合理性。⑤将海相沉积软土的蠕变本构模型应用到填海造陆地区深大基坑变形时空效应的研究中,重点分析了支护桩桩身水平位移、基坑周围地面沉降、坑底隆起、桩身弯矩、桩身剪力和锚索预应力损失的空间特性和时间特性。考虑软土蠕变本构模型的数值分析表明:首先,基坑变形和受力的时空表现不是简单的在基坑拐角处弱,在基坑对称中心处强,具体变形和受力的时空表现与局部软土的厚度、蠕变强弱和开挖顺序等因素有关;其次,基坑东侧因靠近河流,其桩身水平位移和周围地面沉降在基坑各侧中是最大的,因此基坑东侧是整个基坑变形控制的重点区域;最后,对比前人在基坑建模时地层为水平的情况,根据弯曲地层所建立的基坑模型能够更好地反映基坑的实际变形性状。⑥以基坑东侧y=135m处的变形控制为例,在综合分析基坑变形和环境保护的影响因素的基础上,提出多种控制方法组合而成的三种变形控制方案。考虑海相沉积软土蠕变,对以上三种变形控制方案的优劣性进行数值验证。确定了扩大头预应力锚索+坑外主动区注浆是最优的变形控制方案,为填海造陆地区深大基坑的变形控制提供指导。
[Abstract]:With the development of China's city development rapidly, the contradiction between the continuous expansion of the city construction and the limited land resources has become increasingly prominent, therefore, become the coastal city of sea reclamation to increase land reserves, an important way to expand the city space. Now with a variety of high-rise building, high-rise building, a variety of large, complex and super deep foundation pit in the reclamation area of the site came into being, however, the sea reclamation layer under deep marine soft soil is prone to creep deformation in the excavation process, the deformation of supporting structure of foundation pit and the surrounding soil has obvious temporal and spatial effects, in order to safety construction, need to strictly control the deformation time land reclamation. The creep mechanical properties of layer under the marine soft soil is an important factor affecting the deformation of foundation pit, time and space in view of this, based on the predecessors of the Study on creep of soft soil, using a combination of laboratory test, theoretical analysis, numerical simulation, creep mechanical properties of underlying marine soft soil and its constitutive model is studied, and the results are applied to the engineering practice of land reclamation and control area of time-space effect of deep foundation pit deformation. The main research contents and achievements as follows: the systematic research on the foundation of the basic physical properties of marine soft soil and mineral composition, reveals high hydrophilic mineral content, high fines content and high clay content is an important cause of marine soft soil nonlinear creep. The stress controlled three axis instrument, marine soft soil of different depths. At the start of the corresponding consolidation confining pressure under undrained creep test, the creep properties of soft soil to obtain knowledge. Based on the experimental results, focuses on the analysis of marine soft soil in the lower yield stress and higher The yield stress creep characteristics respectively, and the variation of creep properties with time, obtained by the fitting of pore water pressure with the creep time and should function between stress level. The analysis of marine soft soil foundation of linear viscoelastic creep and nonlinear viscoplastic creep law, using the standard linear viscoelastic body description creep, standard linear model and empirical formula were combined to describe the viscoplastic creep, creep to establish element model and empirical model for marine sedimentary soft soil combination constitutive model. Using the classical quasi Newton BFGS algorithm based on MATLAB program, the parameters of soft soil creep constitutive model identification, model parameters high precision, can well describe the creep characteristics at different depths of the marine sedimentary soft soil. Based on the finite difference theory of marine soft soil stress field and seepage field difference control Differential equation; Szsoftsoilmodel.dll. program according to the numerical implementation procedures are confining pressure for 100kPa to achieve the values of creep constitutive model using Microsoft Visual C++6.0 software, the calculation results of creep numerical 200kPa and 250kPa, by comparing the numerical results and the creep test results, verify the correctness of the numerical implementation of the program, which the basis of the engineering application foundation for marine sedimentary soft soil creep model. Establishing the three-dimensional model of deep foundation pit according to the actual fluctuating strata, respectively using the soft soil creep model and Mohr-Coulomb model were used to calculate the horizontal displacement of the retaining pile. The calculation results and monitoring data, the numerical results show that considering the horizontal displacement of the pile of soft soil creep model is better than the Mohr-Coulomb model calculation results of horizontal displacement of the pile is more consistent with the actual verification, the soft soil creep model The numerical implementation procedure for the rationality of foundation pit deformation numerical analysis. The creep of marine soft soil constitutive model is applied to the research on the land reclamation area of the time-space effect of deep foundation pit deformation, analyzes the supporting pile foundation pit horizontal displacement, ground settlement, heave, pile bending moment, the characteristic of space and time the characteristics of pile shear and prestress loss. The numerical analysis shows that the constitutive model of soft soil creep considerations: first, the performance of time and space of foundation pit deformation and stress is not a simple corner in the pit in the center of symmetry at the foundation is weak, strong, specific deformation and stress of the local space performance and thickness of the soft soil, the the creep strength factor and excavation sequence; secondly, the foundation pit near the river, the pile displacement and ground settlement in the foundation pit is the largest, so the East is the whole foundation pit The deformation control in key areas; finally, compared with the previous model in foundation pit formation level, according to the actual deformation of foundation pit formation the bending model can better reflect the foundation. According to control deformation of foundation pit at the east side of y=135m as an example, based on a comprehensive analysis of the influence of foundation pit deformation and environmental factors on and put forward three kinds of deformation control scheme and a combination of various control methods. Considering the marine soft soil creep, numerical verification of the above three kinds of deformation control schemes. The enlarged grouting prestressed anchor cable and pit deformation control scheme of active area is optimal, provide guidance for the deformation control of the sea reclamation area deep pit.

【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU753

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