【作者】 吴明；

【导师】 夏唐代；

【作者基本信息】 浙江大学 ， 岩土工程， 2009， 博士

【摘要】 目前,我国已经进入了新的地下空间开发时代。随着人们对工程问题认识的深入和理论研究发展,基坑工程课题出现了许多新研究方向,但是对原来课题的再认识一刻也未停止。本文针对基坑工程涉及的土压力、变形数值模拟和温度升降对支撑轴力影响这三个问题进行了深入研究。第1章总结了目前基坑工程的研究现状。第2章对于无黏性土提出了一种考虑土拱效应的被动土压力解析式,以及考虑土拱效应土压力的统一解析式。第3章通过改进的基坑分区变形理论,把双曲线土压力模型和Duncan-Chang模型联系起来,可以确定基坑开挖时位移和土压力的关系。将双曲线土压力模型应用于锚碇结构:基于Mindlin弹性解求解了双曲线土压力模型中的初始刚度;采用Log Spiral理论计算该模型中的破坏应力,并且考虑三维效应修正。第4章基于Duncan-Chang模型的思想,摒弃Kondner的双曲线假定,建立了改进切线模量的非线性弹性模型。基于ABAQUS的用户子程序二次开发模块,编写了相应的数值程序,用该程序研究了温州某基坑工程开挖引起围护结构的侧向位移。第5章基于Winkler弹性地基梁模型,对于多层支撑深基坑工程,建立了两种温度升降时各层支撑轴力变化的简化计算方法。第6章总结了本文的研究内容,并提出有意义的研究方向。通过理论分析和算例表明:（1）考虑土拱效应的侧向土压力系数和传统侧向土压力系数存在区别,该侧向土压力系数和主应力旋转角有关。考虑土拱效应的水平向土压力分布更加接近实测值,并且合力作用点不同于传统土压力理论。随着墙土界面摩擦角δ减小,主动、被动土压力合力作用点位置分别从墙上部、下部无限接近墙高H/3处。（2）考虑土拱效应的水平向被动土压力分布沿挡墙高H,上部土压力较小,底部较大。当墙土摩擦角δ从0增大到φ时,被动土压力分布从线性变为非线性,并且挡墙上部土压力越小,而靠近挡墙底部土压力越大。当墙土摩擦角δ等于0时,此时没有土拱效应发生,被动土压力符合Coulomb理论。（3）通过改进的基坑变形分区理论,从新把双曲线土压力模型和Duncan-Chang本构模型联系起来。基坑开挖实例表明,该土压力模型计算结果能反映基坑开挖过程中,主动区和被动区土压力的随开挖位移变化关系。“m”法、“k”法和“c”法中的地基抗力系数m、k′和c′都是一个变化的值。其影响因素有:初始地基反力系数(如:m_max)、应力破坏比R_f、破坏应力p_f、支挡结构位移u和深度z,其中初始地基反力系数影响最大。（4）对于基坑工程中的锚碇结构,可以用双曲线土压力模型反映锚碇板所受荷载和位移的关系。该双曲线土压力模型中:用Mindlin解积分的矩形区域受水平均布荷载时水平向位移弹性解,来定义初始刚度K_max;采用Log Spiral理论计算该模型中的破坏应力,并且可考虑三维效应修正。（5）改进切线模量的弹性非线性模型,不需考虑Kondner的双曲线假定。该模型数学特性良好,参数概念明确且易于确定,并数值上容易收敛,易于程序实现。通过数值模拟三轴试验结果对比表明,改进切线模量的弹性非线性模型可以使模拟结果围绕在实测应力—应变关系资料周围,把结果控制在一定范围内。用该程序模拟具体基坑工程,表明改进切线模量的弹性非线性模型可以应用于实践,并且可以在一定范围内体现岩土工程的求解值。（6）建立2种可以考虑温度升降对各层支撑轴力影响的简化计算方法,模型可以反映支撑—围护结构—土互相协调变形的过程。对两层支撑的例子分析结果表明,其误差分别占支撑总轴力的10.4%,7%;多层支撑温度变化引起底部支撑的轴力变化最大,上部次之。更多还原

【Abstract】 Nowadays,a new era of exploring the underground space has come.As both the knowledge of engineering problems and the theory research develops,a lot of new excavation problems have turned up.However,the further consideration for the original questions is still being carried on.This article has done deep research on the following three aspects on excavation engineering:the earth pressure of retaining wall,the numerical simulation for deformation and temperature fluctuations influence on the axial force of structs.The first chapter has drawn a conclusion on the recent research situation of the foundation pits.And the second chapter has put forward an analytical expression of the passive earth pressure for cohesionless soil,which takes soil arching effect into account.Then in the third chapter,based on the Mindlin’s elastic solution,the initial rigidity of this model has been solved.After that,the ultimate stress of this very model has been calculated using the Log spiral’s theory with considering the three-dimension effect modification.In the fourth chapter,based on the Duncan-Chang model theory and the Kordner’s hyperbolic curve assumption’s being banished,the expression of improved elastic non-linear tangent modulus has been established.And then,based on ABAQUS user subroutine,a corresponding numerical program has been written.This program has been employed to research the variation of the lateral displacement in the excavation in Wen Zhou.The fifth chapter,based on the Winkler’s elastic foundation beam model,established the simplified calculation method for calculating temperature stress in multi-layer for deep excavation considering temperature variation.Finally,the sixth chapter has concluded all the research in the article.And some promising researching directions have been put forward,through the theoretical analysis and the calculation examples.(1) The lateral earth pressure coefficient considering soil arching effect is related to the rotation angle of principal stress.And this new lateral earth pressure is closer to the actually measured earth pressure.As the friction angle of the wall-soil interface decreases,the action points of the active earth pressure resultant and the passive one infinitely approach to the H/3 of the wall from the upper and lower part of the wall respectively. (2) As the friction angle increases form 0 toφ,the distribution of the passive earth pressure turns from linear to non-linear,and the earth pressure on the upper part of the wall becomes smaller whereas the pressure on the lower part turns larger.Especially,when the friction angle equals 0,there is no soil arching effect,and the passive earth pressure coincides with the Coulomb theory.(3) Through the theory of subzones of excavation,the hyperbolic earth pressure model and the Duncan-Chang’s constitutive model has been connected.In a real engineering example,the calculation based on this combined model can illustrate the relationship between the earth pressure and the lateral displacement in the active zone and passive zone.The subgrade resistance coefficient varies with the initial resistance coefficient,the stress failure ratio R_f,the failure stress p_f,the displacement of the bracing system and the depth z,of which the initial subgrade resistance coefficient is the most significant factor.(4) Based on the Mindlin’s elastic solution,the lateral displacements of some rectangular region underground have been calculated when it is bearing lateral loads.Through this solution, the initial rigidity of the hyperbolic non-linear earth pressure model was defined.And the Log Spiral’s theory was used to calculate the ultimate stress,which has taken the three-dimension effect modification into account.In addition,by an anchor experiment,the relationship between earth pressures and displacements is well reflected.(5) Because of no Kordner’s hyperbolic assumption,the expression of improved elastic non-linear tangent modulus is more reasonable than that of the Duncan-Chang.Through the numerically simulated triaxial test,the results can be controlled within a certain range using this expression of improved modulus.What’s more,by a simulated foundation pit’s excavation,it shows this expression of improved elastic non-linear tangent modulus can be applied to practice, and the solution of the geotechnical engineering can be embodied to some extent.(6) Two simplified calculation methods for calculating temperature stress of bracs when temperature fluctuations.The models consider the process of brace-pile-soil interaction.There are many influential factors,such as structural forms of the support,the integral rigidity of the bracing system,the deformational modulus of the soil,and so on.Through the analysis of a pit with two-layer struts,the errors accounts for 10.4%and 7%of the total axial force respectively. In general,with the fluctuation of temperature,the axial force at the bottom changes the most whereas the upper one changes less.更多还原