【作者】 张杰；

【导师】 刘保国；

【作者基本信息】 北京交通大学 ， 土木工程， 2018， 硕士

【摘要】 本文以深圳至中山跨江通道沉管隧道项目为工程背景,通过室内单轴压缩蠕变试验,研究了沉管隧道下卧软土层的蠕变特性。基于蠕变试验规律,选择Burgers蠕变本构模型描述下卧软土的流变特性,通过拟合蠕变试验数据得到Burgers模型的模型参数,结合Burgers蠕变模型参数利用FLAC3D建模分析了沉管隧道的沉降规律,依据沉降计算结果提出了具体的沉降控制措施。主要研究方法和成果如下:(1)采集了“深中通道”沉管隧道E25～E29管段下卧土层中的粉质黏土和E1～E5管段下卧土层中的黏土试样。通过室内试验,分别测得粉质黏土和黏土的密度ρ、含水率ω、土粒比重Gs、粘聚力c、内摩擦角φ和单轴抗压强度σ。(2)进行了粉质黏土和黏土的单轴压缩蠕变试验,得到了粉质黏土和黏土的蠕变规律。试验发现:这两种土的流变性都很大,蠕变变形占总变形的比例集中在83%～94%之间;粉质黏土的蠕变速率在前3～5个小时很大,黏土的蠕变速率在前6～10个小时都比较大,之后蠕变速率均迅速减小并趋于稳定。(3)分析了典型蠕变模型的特点和适用性,根据蠕变试验规律选择Burgers模型来描述沉管下卧软土的蠕变特性,先利用一维状态下Burgers模型的蠕变方程拟合试验数据,再利用蠕变参数中弹性和粘性参数的转换关系,得到三维状态下Burgers模型的蠕变参数。(4)基于Burgers模型的蠕变参数,利用FLAC3D进行数值模拟,分析沉管隧道的沉降规律。计算在考虑流变和不考虑流变条件下,下卧层为粉质黏土和黏土时下卧层的变形规律和沉管隧道的沉降规律,并与考虑穿越层流变下卧层为砂土时沉管隧道的沉降进行对比。结果表明:当下卧层为粉质黏土时,下卧层变形和沉管隧道沉降比黏土时要大;在考虑流变条件下,下卧土层变形和沉管隧道沉降均比不考虑流变条件时要大;下卧层为软土和非软土的衔接处沉管隧道会产生较大的不均匀沉降,需对软土基础进行加固处理。(5)分别从内因和外因两个方面分析了引起沉管隧道沉降的因素,分别给出了施工期和运营期沉管隧道的沉降控制措施,结合“深中通道”沉管隧道下卧土层的分布情况和沉降计算结果,给出了其基础处理方案。更多还原

【Abstract】 This paper takes the Shenzhen to Zhongshan cross-river immersed tunnel project as the engineering background.Through the uniaxial compression creep test,the creep characteristics of the soft soil under the immersed tube tunnel are studied in this paper.Based on the creep test law,the Burgers creep constitutive model was selected to describe the rheological characteristics of the soft soil in the lower lying soil.The model parameters of the Burgers model were obtained by fitting the creep test data.Combined with the parameters of Burgers creep constitutive model,the settlement law of the immersed tube tunnel was analyzed by using FLAC3D model,and concrete settlement control measures were put forward according to the settlement calculation results.The main research methods and results are as follows:(1)The silty clay samples in the lower soil layer of the E25～E29 pipe section and the clay samples in the bottom of the E1～E5 pipe section of the immersed tube tunnel between Shenzhen and Zhongshan were collected.The density p,water content ω,soil particle gravity Gs,cohesive c,internal friction angle φ and uniaxial compressive strength σ of the silty clay and clay are measured by indoor experiments.(2)The uniaxial compression creep tests of silty clay and clay were carried out,and the creep laws of silty clay and clay were obtained.It was found that the rheological properties of these two kinds of soil were very large.The proportion of creep deformation in the total deformation was concentrated between 83%～94%.The creep rate of silty clay was very large in the first 3～5 hours,while the creep rate of clay was large in the first 6～10 hours,and then the creep rate decreased rapidly and tended to stabilize.(3)The characteristics and applicability of the typical creep model were analyzed.According to the creep test rule,the Burgers model was selected to describe the creep characteristics of the soft soil under the immersed tube.First,the creep equation of the Burgers model in one dimension state was used to fit the test data,and then the creep parameters of the Burgers model in the three-dimensional state were obtained by using the transformation relationship of the elastic and viscous creep parameters.(4)Based on the creep parameters of Burgers model,the numerical simulation of FLAC3D was used to analyze the settlement law of the immersed tube tunnel.The deformation law of the lower lying layer and the settlement law of the immersed tunnel were analyzed under the condition of rheology and without considering the rheological condition when the lower lying layer is the silt clay or the clay soil.Then,they were compared with the settlement of the immersed tunnel when the underlying layer is sandand considering the rheology of the stratum of the immersed tunnel crossing.The results showed that when the lower lying layer is silty clay,the deformation of the lower lying layer and the settlement of the immersed tube tunnel are both larger than that of the clay.Under the rheology condition,the deformation of the lower lying layer and the settlement of the immersed tube tunnel are larger than that under non-rheological condition.The immersed tube tunnel at the junction of the lower Stratum layer is the soft soil and the non-soft soil will produce larger uneven settlement.It is necessary to reinforce the soft soil foundation.(5)The factors causing settlement of immersed tunnel are analyzed from two aspects of internal and external reasons,and control measures of immersed tunnel settlement are given out in the construction period and the operation period respectively in this paper.Combined with the distribution of lower soil layer and the settlement calculation results of "Shen zhong channel" immersed tunnels,the foundation treatment scheme is given.更多还原