【作者】 董金梅；

【导师】 刘汉龙； 洪振舜；

【作者基本信息】 河海大学 ， 岩土工程， 2005， 博士

【摘要】 聚苯乙烯轻质混合土是刘汉龙教授等人开发的一种新型轻质填土材料(专利申请号为02112812.X)。在室内试验的基础上，对其物理、强度和变形特性进行了系统、深入地研究，主要内容包括： (1) 通过混合土密度的测定，得到其随配比的变化规律：聚苯乙烯颗粒含量是影响密度的主要因素，水泥掺入比、含水量、原料土的土质对密度也有影响；试验方法、养护条件对密度也有一定影响。研究密度的影响因素，对于设计其工程应用密度具有重要意义。 (2) 在无侧限抗压强度试验和三轴压缩试验的基础上，研究了该混合土的应力应变特性：水泥掺入比、含水量、密度和龄期对单轴应力应变特性有不同程度的影响；UU试验和CU试验的应力应变特性，也因配比和龄期不同而有所不同。 (3) 单轴、三轴应力应变曲线的拟合结果表明：单轴应力应变曲线符合双曲线模型和软化曲线模型，三轴应力应变曲线符合弹性-幂次强化模型，为今后轻质混合土本构模型的研究和有限元分析中计算模型的选定提供参考。 (4) 为了定性地了解混合土的破坏方式和变形计算参数的变化规律，研究了破坏应变的影响因素和变形模量与抗压强度的关系：破坏应变随水泥掺入比、含水量、密度和龄期而变化，与抗压强度呈乘幂关系；变形模量与抗压强度也为乘幂的关系；三轴压缩试验中变形模量随围压的增大而降低。 (5) 通过单向压缩固结试验，研究了该混合土的压缩变形特性：水泥掺入比、密度、含水量和龄期对压缩变形特性均有不同程度的影响，并确定了压缩屈服应力和压缩变形模量，为控制轻质混合土在工程中的沉降变形提供依据，对其压缩变形与时间的关系作了初步探讨，认为混合土的变形大部分为瞬时沉降变形。 (6) 抗压强度随配比的变化规律研究：首先对单轴抗压强度随水泥掺入比、密度、含水量和龄期的变化规律进行了分析，为根据目标强度确定混合土的配比提供依据；然后通过水泥掺入比和水泥含量的换算，得到抗压强度的经验计算公式，便于工程应用；综合考虑了影响聚苯乙烯轻质混合土抗压强度的主要因素，结果表明，水泥含量是主要影响因素，其次是含水量，龄期，EPS颗粒含量的影响通过密度体现出来，对抗压强度的影响很小。 (7) 抗压强度与屈服应力之间的关系：根据无侧限抗压强度试验、三轴压缩试验和单向压缩固结试验的结果，分析了抗压强度与压缩屈服应力的关系、弹性极限和抗压强度的关系、三轴压缩试验的屈服应力与围压的变化关系，根据抗压强度确定具体工程中的上部荷载、屈服应力等。 (8) 三轴压缩试验的抗剪强度特性研究：CU试验的强度包络线近似符合摩尔库伦摘要强度理论，而UU试验则不符合摩尔库仑强度理论。水泥掺入比、密度和龄期对抗剪强度指标(粘聚力和内摩擦角)均有影响。。 本文通过对聚苯乙烯轻质混合土工程特性的试验研究，为其今后在岩土工程领域的进一步研究和应用提供科学依据。关键词:聚苯乙烯轻质混合土，应力应变特性，抗压强度，水泥掺入比，密度，含水量， 龄期，压缩变形特性更多还原

【Abstract】 Being a new kind of light filling materials, Lightweight Soil Mixed with Expanded Polystyrene(hereafter as LSM-EPS) has been developed as a new technique for foundation treatment at present(Patent No.:02112812.X).It has different characteristics from conventional soil materials. Based on laboratory tests, the physics, strength and deformation characteristics of LSM-EPS are studied deeply in this paper in the view of the application in engineering. In concrete, it includes the works as follows:(1) Based on testing the density of the LSM-EPS at different mixing proportion, its density change rule varied with mixing proportion is obtained. The results of tests indicate that the content of expanded polystyrene grains is the main influence factor to the density of LSM-EPS. The cement-mixed ratio, water content and the properties of soil also have some influences to it. 7 days later, the density is almost independent of the age. The testing methods, curing conditions and so on have some influence to the density. That should be paid attention to during the test. It has a comparative significance to study the change rule of density of LSM-EPS with different cement-mixed ratio, water content, EPS grains content, and age and so on for adjusting the required density.(2) Based on unconfined compressive tests and triaxial shear tests, the stress-strain properties of LSM-EPS are analyzed. The results indicate that the uniaxial stress-strain curves are affected by cement mixed ratio, water content, density and age at various degrees. That means the properties of stress-strain are influenced by mixing proportion apparently. The stress-strain properties of the UU test and CU test are different with the different mixing proportion and ages.( 3 ) The simulation of stress-strain curves. The uniaxial and triaxial stress-strain curves are simulated .The results indicate that a hyperbolic model and strain softening model can reasonably simulate the stress-strain relations under uniaxial stresses conditions and a elastic-linear hardening model can reasonably simulate the stress-strain relations under triaxial stresses conditions. It can be made the base for constitutive model of LSM-EPS.(4) The influence factors for failure strain and deformation modulus of LSM-EPS are analyzed. Tests results demonstrate that failure strain changes with the change of cement mixed ratio, water content, density, age and has a linear relation with the compressive strength, while deformation modulus and compressive strength have the same relation. Deformation modulus is decreased with the increasing of confining pressure in the triaxial compression test. It’s main for finding out the failure mode and acquiring the deformationcalculation parameters of mixed soil.(5) Compression deformation characteristic of LSM-EPS is analyzed according to uniaxial consolidation compression tests. Test results show that cement mixed ratio, density, water content, and age have an influence on compression deformation characteristic in different level. On this base, the compressive yield stress and compressive deformation modulus of LSM-EPS are confirmed, which provide the gist for controlling the deformation quantity of LSM-EPS during engineering. The relation between deformation and time of mixed soil during compression is made a pilot study. It takes for that most of the deformation of mixed soil is finished momently.(6) The change rule of compressive strength for LSM-EPS is analyzed. Firstly, the rule of uniaxial compressive strength changing with cement-dosage, water content, density and age is analyzed, which provide the basis for determining the mixing proportion according to the aim strength. After conversion between the cement mixed ratio and the cement content, the experienced calculation formula are obtained, which are convenient for engineering application. The main influence factors to the compressive strength of LSM-EPS are considered synthetically. Results show that cement content is the mostly influence factor to the compressive strength of LSM-EPS, and更多还原