【作者】 陶高梁；

【导师】 张季如；

【作者基本信息】 武汉理工大学 ， 结构工程， 2010， 博士

【摘要】 岩土多孔介质作为一种特殊的工程材料,其工程性质具有复杂性和变化性,而这种复杂性和变化性主要受其微观或细观结构的控制,因而对其微观结构进行研究具有极其重要的意义。岩土多孔介质微观孔隙和颗粒的大小和形状相异,表现出“无序”的特征。大量研究表明它们表现出分形特性,因而分形理论成为岩土介质微观、细观特性研究的有效手段。基于分形理论,本文对岩土介质孔隙结构展开研究工作,目的旨在推动岩土多孔介质的微观结构研究。论文首先对岩土多孔介质的分形模型进行深入研究,提出了两大类模型。这两类分形模型能将国内外模型统一起来,从而形成了两类统一的模型,有效避免了分形模型的错用。论文对岩土多孔介质的分形维数进行了系统的归类与定义,并研究它们之间的关系。建立了二维和三维空间分维数之间的联系,从而可以通过二维数字图像技术估算岩土多孔介质在三维空间的分维数。证明了颗粒原状面积(体积)分布分维数与孔隙原状面积(体积)分布分维数在有限尺度范围内能同时存在,并给出了两者之间的关系式。黏性土的微观结构实验数据表明：通过此关系式可有效估算孔隙原状面积分布分维数。建立了土壤黏粒含量与其颗粒质量～粒径分布分维数的关系,大量的实验数据证明了它的有效性。论文采用土壤切片技术、SEM技术、压汞技术及数字图像技术获得了水泥基环境岩土材料、软黏土的孔隙分布数据,在此基础上研究了取样深度及干湿循环对水泥基环境岩土材料孔隙分布的影响,研究了固结压力对软黏土孔隙分布的影响。利用软黏土和水泥基环境岩土材料在二维和三维空间内的孔隙实验数据证明了本文提出的分形模型的合理性。论文探讨了分维数求解方法对岩土多孔介质的孔隙分形特性的影响,结果表明本文提出的分维数求解方法比已有方法更为方便、有效、合理。论文对孔隙分布的定量化描述进行了深入研究,提出了3种描述孔隙孔径分布的孔隙率模型,并利用黏土和水泥基环境岩土材料在二维和三维空间内的孔隙实验数据研究其适用性,结果表明：三维空间内,第3种孔隙率模型预测值与实测值吻合很好,二维空间内,模型的有效性与相应的孔隙数量-孔径分布分维数大小紧密相关。利用提出的描述孔隙孔径分布的孔隙率模型,给出了基于土体微观孔隙结构的固结变形计算公式,在低固结压力下压缩应变计算值与实测值相差约0.007；建立了多种非饱和土的土-水特征曲线模型,从形式上包含了现有的土-水特征曲线模型,由于模型中的颗粒原状面积(体积)分布分维数能反映孔隙分布特性,因而建立的土-水特征曲线模型更为合理；最后给出了土体黏聚力及岩土介质体积密度与样本尺寸的关系式,从而验证了黏聚力及体积密度随样本尺寸增大而减小的规律。更多还原

【Abstract】 As special engineering materials, rock and soil porous media show complicated and diverse engineering properties, which are controlled by their microstructures (or mesostructures), so it is very important to make deep research on their microstructures. The grains and pores in rock and soil porous media vary in shape and size, displaying disordered properties. However, in many other studies it has been shown that they are fractals. Consequently, the fractal theory has become accepted as a valid means to study the microstructures of rock and soil porous media. By using the fractal theory, the study on pore structure of rock and soil porous media was carried out and some valuable conclusions were gained.At first, two categories of fractal models of rock and soil porous media were established in this study. It was found that previous models can be unified by the two categories of fractal models, so the unified fractal models were formed.Afterward, the fractal dimensions of rock and soil porous media were classified and defined. A new method was presented to estimate the fractal dimensions in 3D space from the 2D structures of rocks and soils, thus the technique of digital image in 2D can be easily applied to obtain the fractal dimensions in 3D space. This study shows that the grain area (volume) fractal dimension and the pore area (volume) fractal dimension can exist simultaneously on a finite scale. The expression for the relationship between the two fractal dimensions was established. The experimental results of the microstructure of clay indicate that the expression is valid for estimating the pore area fractal dimension. The expression for the relationship between the fractal dimension of grain mass vs particle-size and the clay contents was founded, and its rationality has been verified by many experimental results.By using soil micromorphology technique, the mercury intrusion technique, the scanning electron microscope (SEM) and image analysis technique, the pore-size distributions of ecotypic revetment material (eco-material) and soft clay were gained. Moreover, the effects of soil depth and wet-dry cycling on the pore property of eco-material and the effects of consolidation pressure on the pore property of soft clay were investigated.Experimental results of pore distributions of soft clay and eco-material show the fractal models presented by this study are rational. The relationship between the calculation methods of fractal dimensions and the fractal behaviors of materials was studied. The results show the calculation methods of fractal dimension presented by this study are more effective and rational than previous means.At last, three new porosity models were developed to describe the pore-size distributions of porous media. Pore-size distributions of soft clay and eco-material in two- and three-dimensional spaces were used to study the applicability of proposed porosity models. The results show that the new porosity models are valid in describing the pore-size distributions of rock and soil samples.Based on the new porosity models, a new microstructure soil consolidation model was developed and the error of the compression strain prediction was less than 0.007 under low pressure. Several models for soil water retention curve were founded, which in form comprise previous models developed by other researchers, and they may be more accurate than previous models because of the valid mean for determining the fractal dimension. In addition, we obtained an expression for the relationship between soil cohesion and the test specimen size, as well as between the bulk density of rocks and soils and the test specimen size.更多还原