Microfracture and Repeated Plastic Deformation in Unsaturated Soils as Influenced by Surficial Properties

这个项目是为了确定非饱和土壤的经验强度和塑性变形特性与土壤颗粒、水和溶解在水中的盐的更基本的物理、化学和热力学特性之间的关系。更基本的性质是指亥姆霍兹表面能、润湿和脱湿角、溶液浓度、土壤颗粒的粒度级配以及土壤、水和空气的体积浓度。这些被认为是非饱和土壤断裂和愈合特性的基础，并解释了重复加载下土壤的对数加工硬化、屈服和塑性潜在特性。据研究小组所知，过去很少有人利用最近在聚合物中建立的土壤粘弹性特性、亥姆霍兹表面能和土壤断裂中耗散的“伪应变”能的变化率之间的联系。此外，最近发现，在重复加载下，耗散伪应变能的变化率解释了非饱和土等复合材料的塑性加工硬化。这个提议的项目的目的是探索这些连接无限颗粒非饱和土，看看是否可以做出相同的连接。本文还提出确定渗透水势对土壤断裂和塑性特性的影响。渗透电位与孔隙水中溶解的有机或无机盐的浓度有关。孔隙水中溶质浓度的一个主要影响是改变润湿或脱湿角。众所周知，有些盐会增加润湿角，而另一些盐会减少润湿角，因此对土壤的强度有不同的影响。使这些特性的测量成为可能的是最近在德克萨斯a&m获得的德国制造的通用吸附装置，以及最近建造的具有异常广泛能力的三轴非饱和土壤应力路径单元。第一台设备使测量亥姆霍兹表面能的所有组成部分成为可能：利夫希茨范德瓦尔斯极性组成部分和刘易斯酸碱极性组成部分。第二项设备使得在测量机械应力和应变的所有组成部分以及水势的所有组成部分时，对非饱和土壤进行仔细控制的测试成为可能，其范围比过去使用类似设备所达到的范围更大。将这两种测试设备结合在一起的最后一种独特功能是texas A&amp；M最近开发的分析测试数据以确定每个负载周期的耗散伪应变能的能力

***9978672LyttonThis project is to determine how empirical strength and plastic deformationproperties of unsaturated soils are related to more fundamental physical,chemical, and thermodynamic properties of the soil particles, water, and saltsdissolved in the water. The more fundamental properties referred to are theHelmholtz surface energies, wetting and dewetting angles, soluteconcentrations, particle size gradations of the soil particles, and thevolumetric concentrations of soil, water, and air. These are expected tounderlie the fracture and healing properties of the unsaturated soil andexplain the logarithmic work hardening, yield, and plastic potentialcharacteristics of the soil under repeated loading. To the knowledge of theresearch team, there has been little done in the past to make use of theconnection, which has been recently established in polymers, between theviscoelastic characteristics of a soil, the Helmholtz surface energies, and therate of change of dissipated "pseudo-strain" energy in the fracture of thatsoil. In addition, it has recently been discovered that under repeatedloading, the rate of change of dissipated pseudo-strain energy explains theplastic work hardening of a composite material like an unsaturated soil. It isthe purpose of this proposed project to explore these connections infine-grained unsaturated soil to see if the same connections can be made. Itis also proposed here to determine the effect of the osmotic water potential onthe fracture and plasticity properties of a soil. The osmotic potential isrelated to the concentration of organic or inorganic salts dissolved in thepore water. A major effect of the concentration of solute in pore water is toalter the wetting or dewetting angle. It is known that some salts willincrease and other salts will decrease the wetting angle and thus will have adistinctive effect upon the strength of the soil.What makes the measurement of these properties possible is the recentacquisition at Texas A&M of a German-built Universal sorption apparatus and therecent construction of a triaxial unsaturated soil stress path cell withunusually broad capabilities. The first equipment makes it possible to measureall of the components of the Helmholtz surface energies: the Lifshitzvan derWaals apolar components and the Lewis acid and base polar components. Thesecond item of equipment makes it possible to make carefully controlled testson unsaturated soils while measuring all components of mechanical stress andstrain and all components of the water potential over larger ranges than havebeen achieved with similar equipment in the past. The final unique capabilitythat fits these two test apparati together is the ability recently developed atTexas A&M to analyze the test data to determine the dissipated pseudo-strainenergy with each load cycle.***