【作者】 王立峰；

【导师】 朱向荣；

【作者基本信息】 浙江大学 ， 岩土工程， 2003， 博士

【摘要】 水泥土外加剂可以改善水泥土的性能，如适应工程的需要早强、增强、增加抗渗能力和缓凝等等。随着对不同外加剂水泥土的工程特性、改性机理等理论的不断探讨和研究，水泥土被广泛应用于地基处理、边坡加固、基坑围护、注浆堵水等工程中。然而也因为存在水泥土强度不高、变形较大等因素而受到限制。随着纳米技术的兴起和发展，作者把纳米硅粉作为水泥土的外加剂，探讨了纳米硅水泥土的强度特性、变形特性及其影响因素和变化规律，分析了纳米硅作为水泥土外加剂在经济上的可行性，建立了纳米硅水泥土的弹塑性本构关系模型，为纳米硅水泥土在工程上的应用提供理论依据。 在大量试验基础上，本文首先分析了影响纳米硅水泥土抗压强度的因素和变化规律。试验表明，纳米硅对改善水泥土的工程特性，特别是增强水泥土抗压强度，效果明显。纳米硅增强水泥土存在一最佳掺量a_op，超过或低于这一掺量都不能充分发挥纳米硅增强水泥土的作用。其次应用正交试验，定量分析了纳米硅掺量、水泥掺量、水灰比和龄期等因素对抗压强度影响的大小。在对纳米硅水泥土强度特性及大量试验数据整理和分析的基础上，建立了纳米硅水泥土抗压强度与水泥掺量、纳米硅掺量、围压和龄期间的强度关系模型，用此模型可以粗略地估算相同的试验材料在试验条件相同的情况下纳米硅水泥土的抗压强度。以经济学价格理论为指导，分析了工程上应用纳米硅水泥土在经济上的可行性。分析结果表明，当纳米硅价格降至某一临界值时，相同强度的纳米硅水泥土成本低于普通水泥土成本；在此基础上，对纳米硅水泥土成本进行了分析和预测。 分析和描述了纳米硅水泥土受压破坏的过程，解释了试验过程中观察到的一些现象；分上升段和下降段建立了单轴受压下纳米硅水泥土的非线性本构关系模型，给出了模型参数的选取方法和建议值。根据大量的应力—应变关系曲线，讨论了水泥土的破坏应变、变形模量等指标与围压、抗压强度间的关系和统计规律。 以收集到的大量试验数据为基础，以弹塑性理论为指导，得出了纳米硅水泥土在子午面上的破坏曲线。结果表明，低强度纳米硅水泥土破坏曲线在子午面上为直线型，高强度纳米硅水泥土为抛物线型，假定破坏线在π平面上以椭圆线相连，建立了纳米硅水泥土的屈服准则。应用此屈服准则，采用相关联的流动法则和塑性功硬化规律，推导了纳米硅水泥土的弹塑性本构关系模型；给出了硬化模量的一般形式，结合试验数据，可以方便地求出硬化模量。 建立了纳米硅水泥土的弹塑性有限元方程，得到了三轴试验中圆柱体试样和单桩复合地基中的应力分布、变形特性和沉降规律，最后给出了一个工程算例，计算结果表明，在其它因素相同的情况下，纳米硅水泥土的桩基沉降明显小于普通水泥土材料；当纳米硅掺量在最佳掺量范围内，纳米硅掺量大的桩基沉降小于掺量小的桩基沉降。更多还原

【Abstract】 Additives can be used to improve the engineering properties of cement-stabilized soil (CSS), for example, in the engineering, high-early strength, low permeability and retardation of CSS is needed. With the further studies on engineering properties, modified mechanism and work performance of CSS added various additives, CSS has been extensively applied in the ground treatment, slope protection, bracing foundation pit, injection and ponding engineering, etc. However, the use of CSS is restricted due to low strength and large deformation. In this paper, nanometer silicon as additive is applied in the CSS. Strength and deformation property, and its influence factors and variable rule of nanometer silicon and cement-stabilized soil (NCSS) are firstly studied; then economic feasibility is analyzed; finally an elastic-plasticity model is established to provide theory for the use of the NCSS in the civil engineering.Based on lots of laboratory tests, influence factors and variable rules of the NCSS compression strength are analyzed. The results suggest that nanometer silicon can greatly enhance the compression strength of CSS and there exists optimal nanometer silicon content. Through orthogonal tests, the paper quantitatively analyzes the magnitude of the factors influencing NCSS compression strength such as nanometer content, cement content, ratio of water and cement, curing period. On the basis of analysis on testing data, relations between the NCSS compression strength and cement content, nanometer content, confining pressure and curing period are respectively established and these relations can be used to estimate the NCSS compression strength. Guided by Price Theory in Economics, feasibility analysis on application of NCSS in the engineering is presented. Analysis results show that the costs of NCSS will lower than that of the common CSS on the condition of the same strength when the price of nanometer silicon drops to a certain value.Failure process of NCSS in compression is described, phenomena occurred in testing process are explained. Nonlinear constitutive models of NCSS on the condition of single axis stress respectively are established for the rising phase and descending phase of stress-strain curve, and selection method and suggestion value of the models are given. In light of lots of stress-strain relations, statistical laws and relations between failure strain, deformation modulus and confining pressure, compression strength are also discussed.On the basis of abundant datum and elastic-plasticity theory, a general three-dimension failure criterion for NCSS is proposed. Analysis results indicate that failure curves in meridian plane of low strength NCSS are lines, and the curves of high strength NCSS are parabola. Yield criterion is established on the assumption of failure points depicted with ellipse. An elastic-plasticity constitutive model for the NCSS is deduced by the use of the yield criterion, related flow rules and plastic work hardening rules. Proposed hardening modulus can be conveniently obtained according to testing data.Stress distribution, deformation property and settlement laws of cylinder samples in triaxialtests and single pile compound ground are obtained. By an engineering example, analysis shows that the settlement of NCSS piles is smaller than that of CSS piles on the condition of the same factors, and that the settlement of NCSS pile with high nanometer content is smaller than that of NCSS pile with lower nanometer content when nanometer content is in the range of optimal content.更多还原