【作者】 王四巍；

【导师】 高丹盈；

【作者基本信息】 郑州大学 ， 结构工程， 2010， 博士

【摘要】 塑性混凝土是由膨润土、粘土、水泥、砂、石和水等原料经搅拌、浇注、凝结而成的强度介于土和普通混凝土之间的柔性工程材料。为了推广塑性混凝土在工程防渗等领域的应用,本文通过7组不同配合比的塑性混凝土试验,探讨了水胶比、用水量、水泥用量和砂率等参数对塑性混凝土性能的影响,建立了用水量与其余材料用量的关系。在此基础上,通过塑性混凝土的单轴抗压、三轴压缩、单轴循环加载和渗透等试验,研究了单轴受压下塑性混凝土的基本力学性能、三轴压缩下塑性混凝土的本构关系和强度准则、峰值前后两个阶段塑性混凝土的变形特征与其应力状态的关系以及渗透性能等。主要内容如下：1.单轴受压下塑性混凝土基本力学性能(1)单轴抗压性能。研究了加载速率、试件形状、龄期和组成材料等对塑性混凝土单轴抗压强度的影响。结果表明,对于单轴抗压强度大于2MPa的塑性混凝土,适宜的加载速率为0.1MPa/s,小于2MPa时以0.05MPa/s为宜。(2)弹性模量。系统研究了试件形状、量测标距、龄期和组成材料等对塑性混凝土弹性模量的影响。结果表明,塑性混凝土弹性模量试验可采用150mm×150mm×300mm的棱柱体试件以及全长标距测试变形,试验时不预压。塑性混凝土弹性模量应采用应力应变曲线上升段0.3倍和0.7倍峰值强度对应的点建立计算公式,并建立了塑性混凝土弹性模量与立方体抗压强度之间的关系式。(3)单轴受压本构关系。研究了试件形状、龄期、量测标距和测试方式对塑性混凝土单轴受压应力应变曲线的影响,采用上升段和下降段的分段函数方法建立了塑性混凝土单轴受压本构关系。2.三轴应力下塑性混凝土力学性能(1)常规三轴应力下塑性混凝土力学性能。研究了常规三轴试验下围压、单轴抗压强度等对塑性混凝土三轴强度和应力应变关系的影响。结果表明,三轴应力下塑性混凝土强度和峰值应变大幅度提高。建立了三轴强度与单轴抗压强度和围压的关系式、塑性混凝土割线模量与单轴抗压强度、弹性模量以及围压的关系式,并进一步建立了塑性混凝土常规三轴受压本构关系式。(2)真三轴应力下塑性混凝土力学性能。研究了两类真三轴试验下塑性混凝土强度特征。在侧压恒定的真三轴应力下,塑性混凝土强度随侧压的增加而增大；当第三主应力一定时,随着第二主应力的增大,塑性混凝土第一主应力逐渐增加。在侧向位移恒定的真三轴应力下,塑性混凝土三轴强度大幅度增加,且随着设定初始侧向应力的增加而增大,可达单轴强度的4-6倍。研究了真三轴应力下塑性混凝土体应变和峰值应变特征。在侧压恒定的真三轴应力下塑性混凝土出现扩容现象,对于相同配合比的塑性混凝土,在相同的第三主应力下,扩容的起始点随着第二主应力的增大而增大。塑性混凝土立方体试件峰值应变由单轴受压下的0.5%-1.5%增至侧压恒定的真三轴试验下的2%-5%、侧向位移恒定的真三轴试验下的6.2%-9.3%。(3)峰值前后两个阶段塑性混凝土变形特征。研究了塑性混凝土峰值前的变形特征与其应力状态的关系。在单轴压缩及侧向位移恒定真三轴试验下,峰值前塑性混凝土主要产生弹性变形,可用弹性模量表示该阶段变形特征；在侧向应力恒定的常规三轴及真三轴试验下,峰值前塑性混凝土主要产生塑性变形,可用割线模量表示该阶段变形特征。研究了峰值后塑性混凝土应力应变曲线特性与其应力状态的关系。根据峰值后变形性质参数D2 (D2=E1.5ε/E0.3),塑性混凝土峰值后应力应变曲线有如下特点：(4)强度准则。根据常规三轴试验结果,利用格里菲斯理论建立了塑性混凝土强度准则；研究了常规三轴试验下塑性混凝土强度包络线特征并建立了强度方程。根据真三轴试验结果,建立了塑性混凝土破坏准则在八面体应力空间的表达式。3.单轴循环加载下塑性混凝土力学性能研究了4种单轴循环加载模式下塑性混凝土力学性能。根据试验结果,建立了单轴循环加载下塑性混凝土峰值强度与单轴单调加载峰值强度、循环加载过程中最大应力之间的关系式。分析了单轴循环加载下塑性混凝土滞回环的特征及卸载、再加载应力应变曲线特征。4.塑性混凝土渗透性能研究了利用混凝土相对渗透试验和土工渗透试验测试塑性混凝土渗透系数的适宜性。结果表明,利用土工渗透试验测试塑性混凝土渗透系数是不可行的；利用混凝土相对渗透试验测试塑性混凝土渗透系数是可行的,试验时适宜的水压力为0.5MPa、渗透时间为12h,并对试验结果处理方法提出了修正。5.塑性混凝土配合比设计通过7组塑性混凝土配合比试验,推荐了配制不同强度等级塑性混凝土的水胶比、单位用水量、水泥用量、土掺量和砂率等参数,建立了用水量与水胶比、水泥用量、土掺量、砂率的关系式。6.塑性混凝土防渗墙工程应用利用三维有限元方法,研究了塑性混凝土在河南省窄口水库坝体防渗墙的设计与应用。结果表明,塑性混凝土防渗墙技术在该工程中是可行的,防渗墙以两段式最优,下部40m采用C10普通混凝土,上部40m左右采用塑性混凝土并确定了塑性混凝土的设计指标。更多还原

【Abstract】 Plastic concrete is made of bentonite, clay, cement, sand, gravel and water, which is flexible engineering material. In order to use it in cutoff walls extensively, researches were carried on parameters which affected the properties of plastic concrete, such as water cement ratio, unit water, cement, and the relation between unit water and the other parameters was established by 7 plastic concrete mixes tests. Mechanical properties of plastic concrete under uniaxial and triaxial stress were focused using uniaxial compression test, triaxial and true triaxial one, cyclic loading one and permeability one. Main researches were carried on as following:1. Basic mechanical properties of plastic concrete under uniaxial stress(1) Properties under uniaxial compressive stress. Research has been done on the factors influencing strength of plastic concrete, e.g. loading rate, specimen shape, age and constituent. When uniaxial compressive strength of plastic concrete is over 2.0 MPa, the rate should be 0.1 MPa/s, when less than 2.0 MPa, the rate be 0.05MPa/s.(2) Elastic modulus. Elastic modulus of plastic concrete is focused on the influence with specimen shape, standard measurement distance, age and constituent. The result shows that the specimen of 150mm×150mm×300mm, full-lengthed measurement standard stance, should be selected in testing elastic modulus of plastic concrete without preloading. The formula for E can choose the two points of 0.3 and 0.7 times of peak strength on the ascending section in the stress strain curve.(3) Constitutive relation. Stress-strain curve of plastic concrete under uniaxial compressive stress is studied with specimen shape, age, standard measurement distance and constituent. Constitutive equation of plastic concrete under uniaxial compressive stress is established in ascending segment and descending one.2 Mechanical properties of plastic concrete under triaxial compressive stress(1) Mechanical properties under conventional triaxial stress. Main researches are carried on strength and stress strain curve of plastic concrete under conventional triaxial stress. The result shows that strength of plastic concrete increases greatly with confining pressure, and they are established on the relation between the strength of plastic concrete and uniaxial compressive one, confining pressure, and the relation between secant modulus and uniaxial compressive strength, elastic modulus, confining pressure. Furthermore, the constitutive equation under triaxial stress is presented.(2) Mechanical properties under true triaxial stress. Strength of plastic concrete is focused in two kinds of true triaxial tests. The result shows plastic concrete strength increases greatly with lateral pressures, when one of lateral pressure is constant, the strength increases with increases of the other lateral one in the one kind of true triaxial tests. And plastic concrete strength increases more with the increases of the initial lateral pressure, it can reach 4-6 times of uniaxial compressive one in the other kind of true triaxial test.Volume strain and peak one are focused under two kinds of true triaxial tests. The result shows that there is dilatancy for plastic concrete in the one kind of true triaxial test with constant lateral pressure, and the onset of dilatancy increases withσ2 for the constant a3. Peak strain is 0.005-0.015 in the uniaxial compression test, but it can be 0.02-0.05 in the first kind of true triaxial test, and it can be 0.062-0.093 in the second kind of true triaxial test.(3) Deformation characteristics during prepeak and post peak zones. Researches on relations between deformation characteristics and stress state during prepeak zone are carried on. The deformation behaves mainly elastically, when plastic concrete occurs under uniaxial compression test and true triaxial compression one with constant lateral displacement. And elastic modulus is used to represent the plastic concrete deformation characteristics during the prepeak zone. The deformation behaves mainly plastically, when plastic concrete occurs under triaxial compression tests with constant lateral pressure. Secant modulus has been used to assess plastic concrete deformation in the conditions.Researches on relations between deformation characteristics and stress state during postpeak zone are carried on. According to D2 (D2=E1.5ε/E0.3), stress strain curve of plastic concrete behaves as following during post peak zone: (4) Failure criterion. Failure criterion has been studied by Griffith theory and Mohr-Coulomb rules according to plastic concrete conventional triaxial test. Failure criterion in octahedron stress is brought out on terms of plastic concrete true triaxial test.3 plastic concrete mechanical properties under uniaxial cyclic loading testPlastic concrete mechanical properties under 4 kinds of cyclic loading tests is concerned. The equation between peak strength under cyclic loading test and one under uniaxial directly loading test, the maximal stress during cyclic loading is presented. Plastic loop and stress-strain curve of cyclic loading of plastic concrete is analysized.4 Permeability of plastic concretePlastic concrete permeability is studied by comparative permeability test and permeability test in soil mechanics. The result shows that comparative permeability test is good, and the other is bad. The water pressure should be 0.5MPa, and the time be 12h in the comparative permeability test. The modified method of calculation of permeability coefficient is presented.5 Mixes design of plastic concreteParameters are proposed in order to get required strength plastic concrete, including water cement ratio, water, cement and sand ratio.6 Applied of plastic concrete cutoff wall in engineering practiceDesign is analysized on Zhaikou reservoir in Henan province by 3-D FEM. The result shows that plastic concrete cutoff wall can be used in the project, and C10 concrete below 40m and 5MPa plastic concrete for upper segment, and design indexes of plastic concrete are suggested.更多还原