【作者】 张明；

【导师】 赵有明；

【作者基本信息】 中国铁道科学研究院 ， 岩土工程， 2010， 博士

【摘要】 20世纪90年代以来,我国经济建设快速发展,沿海地区土地资源日益紧张,国内沿海地区普遍开展了大规模围海造陆工程,特别是在填海工程中普遍结合疏浚工程、吹淤造陆的方法。吹填土与天然海相沉积淤泥形成的双层地基,具有高含水量、大孔隙比等特点,工程实际表明建立于小变形假定基础上的太沙基固结理论不能准确地预测固结过程,指导设计和施工。所以有必要对吹填淤泥的固结特性和吹填形成的双层软基固结性状开展深入的研究。本文研究工作以“招商局深圳前湾填海造陆软基处理工程”为背景,通过现场与室内试验研究、理论分析和数值分析等方法,对吹填淤泥和海相沉积淤泥的固结特性及双层软基固结性状进行了研究,取得的研究成果如下:(1)吹填淤泥落淤后,仍然发生以自重固结为主的变形,本文推导了以有效应力为变量的一维自重固结方程,该方程考虑了自重固结过程中颗粒体有效应力及渗透系数与体积浓度之间的非线性关系,编制程序SFCCP对方程进行数值求解,该方程能为软基处理前落淤后的土性指标提供一种预测方法。利用程序SFCCP分析了初始压缩性、初始渗透性和初始体积浓度等因素变化对土层孔隙比、体积浓度、自重有效应力、表面沉降及沉降速率的影响,同时对落淤后自重固结过程孔隙比的变化进行了数值模拟,结果与现场试验较为吻合,验证了分析方法的有效性和实用性。(2)利用浙江大学GDS固结仪,对深圳前湾吹填淤泥试样进行了分级加载固结渗透试验,较全面地研究了吹填淤泥的渗透与压缩特性。结果表明,渗透系数、压缩变形参数与孔隙比之间呈现明显的非线性关系,固结计算时需考虑这些参数的变化特性。通过吹填淤泥与天然海相淤泥试验成果分析,总结出了吹填淤泥与天然海相淤泥渗透系数k v、有效应力p′与孔隙比e之间的最优拟合关系为非线性幂函数关系k v= ced与( )e = a p′b。(3)采用Gibson大变形固结理论与Barron轴对称固结问题的某些简化与假定,推导了以超静孔压为变量的双层砂井地基大变形固结控制方程,采用ADI差分格式,编制程序TSDTC进行求解。该程序可考虑双层地基、土体渗透与压缩非线性关系、分级加载、径向与竖向渗流、初始超静孔压分布模式等因素与条件。(4)利用程序TSDTC将算例固结计算结果与已有文献进行对比,两者基本吻合,验证了程序的合理性。进一步分析了非线性渗透关系k v= ced拟合参数、非线性压缩关系e = a p′b拟合参数、土层厚度比、分级加载、初始超静孔压分布模式等对双层砂井地基固结性状的影响。(5)结合深圳前湾填海造陆软基处理工程,利用程序TSDTC对吹填双层软基进行了固结分析,结果表明本文方法预测的固结沉降过程曲线较经典固结理论更接近于实测曲线。本文的研究工作对于认识吹填淤泥工程性质具有重要的理论价值,对于指导围海造陆吹填场地双层软基处理工程具有重要的实际意义。更多还原

【Abstract】 With the rapid development of economic construction and the increasing lack of coastal land resources in China since 1990’s, a lot of land reclamation projects have commenced to conduct for the remission on limited land, especially dredging and land reclamation was commonly used in reclamation projects. Double-layered soft clay foundation of dredged fill and marine deposit silt is characterized by high water content and void ratio, of which the engineering practice showed that Terzaghi consolidation theories based on small strain can not accurately predict the consolidation process, guide the design and construction. Consequently, It is very necessary for the systematic study on consolidation characteristics of dredged fill and consolidation behaviors of double-layered soft clay foundation.In this dissertation, based on the engineering background of“Qianwan Reclamation Soft Clay Foundation Improvement Projects Shenzhen China”, consolidation characteristics of dredged fill and marine deposit silt and consolidation behaviors of double-layered soft clay foundation are studied in detail by means of in-situ tests, laboratory experiment, theoretical analysis, numerical analysis and so on. The main research achievements are shown as follows:Considering of self-weight consolidation deformation as the main effect during self-weight deposition, one dimension self-weight consolidation governing equation of dredged fill is established. The new equation includes the nonlinear relationship between effective stress, permeability coefficient and solid volume fraction, which are solved by the SFCCP computing program. The new equation can also provide a favorable prediction on physical mechanical indices for self-weight deposition. Some significant influence of initial compressibility, initial permeability and initial solid volume fraction on void ratio, solid volume fraction, self-weight effective stress, surface settlement and settlement rate is analyzed by the SFCCP computing program. It is showed that the void ratio results based on the new model are close to the results from in-situ tests, which the effectiveness and practicability of the analytical model are validated.One-dimensional incrementally-loaded consolidation and permeability tests are performed on dredged fill specimens in Qianwan area Shenzhen by GDS consolidation test systems from Zhejiang University. Permeability and compressibility characteristics of dredged fill are studied, it is shown that the relationships of permeability coefficient-void ratio and compressibility parameters-void ratio is nonlinear, which are taken into account variations of parameters. The optimal permeability coefficient-void ratio fitting relationship kv=ced and effective stress-void ratio fitting relationship e=a(p’)b for dredged fill and marine deposit silt are summarized by the analysis of test results.Based on the Gibson one-dimensional finite-strain consolidation theory and Barron vertical sands axisymmetric consolidation theory, a vertical drains and finite-strain consolidation governing equation for double-layered soft clay foundation is established, and solved by the TSDTC computing program. The new program includes some factors of double-layered soft clay foundation, nonlinear compressibility and permeability relationship, multi-stage filling, radial and vertical drainage conditions, initial excess pore pressure distribution.The computing results of consolidation for Florida phosphate mining sludge are compared with the published literatures and the rationality of the computing program is validated accordingly. Consolidation behaviors of double-layered vertical drains foundation are analyzed by the TSDTC computing program. Several influential factors including nonlinear permeability relationship kv=ced fitting parameters, nonlinear compressibility relationship e=a(p’)b fitting parameters, layer thickness ratio, multi-stage filling, initial excess pore pressure distribution are also studied as well.Compared with the classical consolidation theory, based on the observed data in situ, Qianwan Reclamation Soft Clay Foundation Improvement Projects Shenzhen China, it is showed that the consolidation settlement process obtained by the mentioned method in this dissertation is more reasonable.The research achievements in this dissertation will have theoretical values to understand the engineering properties of dredged fill, and also have engineering significance in guiding double-layered soft clay foundation improvement projects in land reclamation.更多还原