【作者】 付建军；

【导师】 刘泉声；

【作者基本信息】 中国科学院研究生院（武汉岩土力学研究所） ， 岩土工程， 2010， 博士

【摘要】 随着我国城市地铁、过江隧道建设的迅速发展,大规模建筑基坑和地下空间的开发利用推动了我国深基坑支护设计与施工技术的进步。但由于深基坑工程涉及的地质条件复杂、不确定因素多,以至于在基坑支护设计与施工中出现了各种各样的问题。武汉长江隧道是长江上第一条隧道,武汉长江隧道引道段、明挖断及盾构井段基坑工程所处二元地质环境,呈狭长型特点,做好其围护体系和防渗体系的研究,对后续武汉地铁过江隧道工程和长江中下游后续类似工程也具有重要的借鉴和指导意义。本文以武汉长江隧道基坑为依托工程,对二元地质环境下狭长型基坑围护体系与防渗体系展开研究。主要研究工作如下：(1)针对桩撑、墙撑支护严格变形控制特征,从主动土压力、静止土压力、被动土压力发生时土体所需位移入手,建立了考虑变形土压力分布模型,研究了基坑土压力分布规律。(2)针对排桩支护坑后土体受力变形特征,从机理上分析水平土拱产生的原因,并根据坑后自由区、土拱区、稳定区三部分土体受力特征,建立相应的力学平衡方程及控制方程,推导了土拱几何参数和桩后土压力,最终将此压力代入自由端法、等值梁法、弹性抗力法进行支护结构内力计算,并对排桩支护进行设计。(3)针对双排桩超静定力学特征,在忽略桩土竖向摩擦效应及空间效应的前提下,对双排桩支护结构力学机理进行了分析,建立了考虑桩间土体效应的双排桩平面杆系有限元模型。并围绕双排桩平面杆系有限元模型的关键参数土压力分布及弹性抗力系数展开了研究,最后编制相应计算程序方便工程设计计算。(4)从工程现场取典型粘性土原状样,加工成标准试件。进行了土体基本物理力学特征试验、固结排水直剪强度试验、高压固结卸荷试验、不同固结压力不同卸荷路径试验,并详细对卸荷试验结果进行了分析,得到了土体卸荷响应下的变形特点、强度特征和破坏规律以及不同卸荷路径下切线模量变化规律,获得了基坑开挖卸荷的土体非线性本构模型的基本力学参数,为进行数值计算提供了依据。(5)详尽分析了不同卸荷路径下土体卸荷试验结果,并根据其大小主应力差与轴向应变关系图进行归一化研究,建立了基坑开挖卸荷的土体非线性模型,且在大型有限差分软件FLAC3D软件平台上将此模型进行了二次开发,最终对依托工程试验段进行了相应的数值分析计算。(6)研究了基坑防渗方法和地下水控制技术,在广泛调查武汉区域地质条件和水文条件基础上,概化了二元地层环境下狭长型基坑地质模型,推导了考虑基坑卸荷影响的渗流微分方程,并编制改进了相应的计算程序,通过计算分析研究开挖卸荷对地下水流场、势场影响,提出了相应地下水控制技术。(7)围绕基坑工程不确性特征,对基坑施工过程中支护结构水平位移、支撑内力、周边土体沉降、周边建筑变形等进行跟踪监测,并对监测结果进行了灰色理论预测、时间序列预测及反馈分析,验证、完善了相关理论研究成果,指导信息化施工。更多还原

【Abstract】 As the rapid development of the construction of urban subway and river-crossing tunnel in china, the development and utilization of large-scale building foundation and underground space promote the progress of deep foundation in support design and construction technology in china. However, because the engineering of deep foundation involving in complex geological condition have many uncertain factors,there are various questions in the support design and construction for foundation. Wuhan Changjiang tunnel is the first tunnel in Changjiang.the guide section、open-cut section and the section for shield well in Wuhan Changjinag tunnel in the environment of binary geological show the character of long-narrow. Doing well in the study of support system and impervious system have important reference and guiding significance.This paper carry out study relying on the foundation of Wuhan Changjiang tunnel.The main research works as follow:(1) According to the characters of controlling deformation strictly with the supports of piles pillared and wall pillared, starting with the required displacement of soil when the active earth Pressure、static earth Pressure or passive earth pressure happened, the model for the earth pressure distribution considering deformation is built, the study about earth pressure distribution in foundation is carried out.(2) According to the deformation character in force of row piles for supporting the soil behind pit, the reason for the formation of horizontal soil arch is analyzed in mechanism. Moreover, based on the character of soil in force for the three zones behind pit, which are the free zone, the zone generating soil arch and the stable zone respectively, the relative mechanical equilibrium equations and governing equations are set up, geometric parameters for soil arch and the earth pressures behind piles are derived, finally the pressures are substituted into free end method, equivalent beam method, elastic resistance method to calculate the internal force of supporting structural, and the support for row piles is designed.(3) In view of the mechanical property of statically indeterminate, in the premise of neglecting the friction effect in vertical between pile and soil and space effect, mechanical mechanism of supporting structure for double-row piles is analyzed, the finite element model of plane bar system for double-row piles which take soil effect between piles into account is set up. And centering on the key parameters of the finite element model of plane bar system for double-row piles, which are earth pressure distribution and elastic resistance coefficient, study is carried out. Finally relevant calculation program is compiled to make engineering calculation convenient.(4) Obtaining typical undisturbed cohesive soil samples from engineering site and processing into standard samples.Basic physical and mechanical features tests are carried out, as well as consolidated drained direct box shear strength tests, high pressure consolidation unloading tests and the tests in different pressures and different paths.Moreover, the results of unloading tests are analyzed in detail.Therefore,the deformation characteristics, strength characteristics and failure laws of soil in unloading response are obtained, as well as the change rule of tangent modulus in different unloading paths.In addition, the basic mechanical parameters for unloading nonlinear soil constitutive model are achieved to provide evidence for numerical calculation. (5) The results of soil unloading tests in different unloading paths are analyzed in detail. Based on the normalized study for the principal stress difference and the relation graph of axial strain, soil unloading nonlinear model are set up. And in the platform of FLAC3D which is a large finite difference soft, this model is second developed. Finally, the test section based on project is carried out relative numerical analysis calculation.(6) The impervious method for foundation and the control technology for groundwater are researched. On the basic of extensively investigating geological conditions and hydrological conditions in Wuhan area, the long-narrow foundation geological model in the environment of binary strata is generalized, percolation differential equation involving in the effect of foundation unloading is derived, relevant calculation program is compiled and improved. Moreover, by means of calculation analysis to analyze the influence of flow field and potential field of groundwater with foundation unloading, relevant groundwater control technology is put forward.(7) Centering on the uncertainty character for foundation pit, horizontal displacements of supporting structures in excavation during construction are track monitored, as well as brace forces and the deformation of surrounding buildings.And monitoring results are predicted with grey theory and time series and feedback analyzed. Besides, relevant theoretical research results are verified and improved to guide information construction.更多还原