流变相物质对软土流变特性影响试验与分析

发布时间：2018-01-10 01:07

本文关键词：流变相物质对软土流变特性影响试验与分析　出处：《华南理工大学》2014年博士论文　论文类型：学位论文

【摘要】：软土是一种广泛分布于沿海、江河、湖泊和湿地等地区的复杂天然多孔介质，近年来随着经济的发展和城镇化水平的不断提高，软土工程的开发和利用不断发展。大量工程经验和研究表明，软土的变形需要较长时间才可达到稳定。软土的这种应力应变随时间发展不断变化的流变特性，可能会使修建在软土地基上的建(构)筑物产生不可忽视的工后沉降，并由此带来安全稳定性方面的问题。有鉴于此，本文采用试验与理论研究相结合的手段，从细观角度分析影响软土强度和流变特性的物质因素和作用机理。通过不同细观参量组合的砂性土和软土试样的强度及流变特性试验，分析各细观参量与强度和流变特性参数间的内在关系，探索影响砂性土和软土强度特性的作用机制，以范性流变和流质流变解释砂性土和软土两者不同的流变特性。最后，在试验分析的基础上，探索流变相物质形状与分布对流变特性的影响，并通过数值模拟计算验证相应结论的正确性。本文开展的研究工作和取得的成果主要有如下几个方面： (1)研究不同粒度成分、矿物成分和含水量的砂性土和软土的强度特性。基于试验分析，认为砂性土的颗粒级配是影响其强度特性的重要因素；而对于软土，不同矿物颗粒之间的吸附与摩擦、胶结作用是其强度特性的决定因素。此外，颗粒表面结合水膜厚度与性质的变化将改变颗粒之间的吸附与摩擦、胶结作用机制，进而改变其强度特性。 (2)采用直剪蠕变试验研究土体成分对流变特性的影响。试验结果表明，粒度成分和应力水平对砂性土流变特性会产生较为显著的影响，同时含水量在一定程度上也会影响其流变特性；软土中的粘土矿物、氧化物、有机质和结合水是土体产生流变的重要物质因素，且都是通过颗粒表面吸附结合水来对软土流变特性产生重要影响的，但不同成分对土体流变特性影响的程度有所不同；结合水性质也会对土样流变特性产生重要影响，强结合水对流变性的影响要比弱结合水显著。 (3)运用四相物质流变理论从物质组成上解释砂性土和软土的流变机理。将土体流变分为范性流变和流质流变，砂性土流变主要受到应力水平和粒度成分的影响，变形稳定所需时间较短，主要表现为范性流变特征，而软土流变则主要受到粘土矿物、有机质、氧化物胶体及结合水等物质含量的影响，变形稳定所需时间较长，表现为流质流变特征。 (4)通过室内蠕变试验和数值模拟计算，分析流变相物质形状与分布对流变特性的影响。试验与数值计算结果表明，当流变相物质的分布较不均匀时，流变相物质形状与分布形式对流变特性的影响较大，但随着流变相物质分布均匀性逐渐增加，流变相物质形状与分布形式的影响逐渐减弱，流变特性逐步过渡到仅与流变相物质性质和比例相关，而与其形状及分布形式无关。
[Abstract]:Soft soil is a kind of complex natural porous media widely distributed in coastal, river, lake and wetland areas. In recent years, with the development of economy and the continuous improvement of urbanization level. The development and utilization of soft soil engineering. A large number of engineering experience and research show that the deformation of soft soil needs a long time to achieve stability. May cause the building (construction) on the soft soil foundation to produce the after construction settlement which can not be ignored, and thus brings the safety and stability aspect question. In view of this, this article uses the method which the experiment and the theory research unifies. In this paper, the material factors and mechanism influencing the strength and rheological properties of soft soil are analyzed from the point of view of meso. Based on the tests of the strength and rheological properties of sand soil and soft soil samples with different meso-parameters, the relationship between the meso-parameters and the strength and rheological parameters was analyzed. This paper explores the mechanism of influencing the strength characteristics of sandy soil and soft soil, and explains the different rheological characteristics of sand soil and soft soil by norm rheology and fluid rheology. Finally, on the basis of experimental analysis. The influence of the shape and distribution of fluid phase material on rheological properties was investigated and the validity of the corresponding conclusions was verified by numerical simulation. The research work and the results obtained in this paper are mainly as follows: 1) the strength characteristics of sandy soil and soft soil with different particle size composition, mineral composition and water content are studied. Based on the experimental analysis, it is considered that the grain gradation of sandy soil is an important factor affecting its strength characteristics. For soft soil, the adsorption and friction between different mineral particles, cementation is the decisive factor of its strength characteristics. In addition, the change of the thickness and properties of water film on the surface of particles will change the adsorption and friction between particles. The cementation mechanism changes its strength characteristics. 2) the effect of soil composition on rheological properties is studied by direct shear creep test. The results show that the grain size composition and stress level have a significant effect on the rheological properties of sandy soil. At the same time, the water content will also affect its rheological characteristics to some extent. Clay minerals, oxides, organic matter and bound water in soft soil are important material factors to produce rheological properties of soft soil, and they all have important effects on rheological properties of soft soil by adsorption of water on the surface of particles. However, the degree of influence of different components on the rheological properties of soil is different. The properties of bound water also have an important effect on the rheological properties of soil samples, and the effect of strong bound water convection is more significant than that of weakly bound water. 3) the rheological mechanism of sandy soil and soft soil is explained by using the theory of four-phase material rheology. The rheology of soil is divided into normal rheology and fluid rheology. The rheology of sandy soil is mainly affected by the stress level and particle size composition, and the time required for deformation stability is relatively short, mainly showing the characteristics of normal rheology, while the rheology of soft soil is mainly affected by clay minerals and organic matter. The effect of the content of oxide colloid and bound water on the stability of deformation takes a long time and shows the rheological characteristics of fluid. 4) the influence of the shape and distribution of fluid phase material on the rheological characteristics is analyzed by indoor creep test and numerical simulation. The results of experiment and numerical calculation show that the distribution of fluid phase material is not uniform. The shape and distribution of fluid phase matter have a great influence on rheological properties, but with the increasing of the uniformity of fluid phase matter distribution, the influence of flow phase material shape and distribution form gradually weakened. The rheological properties are gradually related to the properties and proportions of rheological materials, but not to their shape and distribution.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU447;TU411

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