3-D Characterization and Analytical Description of Desiccation Cracking

这项研究的重点是干燥开裂，并需要通过无损检测技术或应用程序的发展，以开发裂纹几何形状的几何信息细粒度的土壤，容易发生变化的属性，包括强度，体积关系，和水力特性。 拟议的研究的目的是开发一种超声波无损检测技术，以确定干燥裂纹在粘土土壤的深度，并涉及到各种粘土性质的开裂深度。 研究人员将制定一系列与裂缝的发展和扩展有关的预测方程，例如：裂缝深度，表面裂缝密度和裂缝扩展速率，作为塑性和活性，矿物学，初始含水量，压实条件和土壤强度的函数，以及应用于土壤的润湿和干燥循环。 将进行实验分析的裂纹特性，包括土壤水分吸力对应于裂纹萌生，扩展深度，survival几何形状，裂纹扩展速率，并通过裂纹的水分通量，重点是对土壤的水力特性开裂的影响。 该研究将通过实验确定裂缝存在时通过粘土的流量的变化。 超声波方法将提供一个创新的工具来分析土壤中的裂缝深度，并将与以前开发的图像分析技术一起使用，以确定裂缝的3-D特性。这两种方法可以应用于分析拉伸裂缝，冻融裂缝，或任何其他类型的裂缝在土壤中发展。 超声波设备也可以很容易地运输到现场进行测试，干燥过程的照片是图像分析所需的唯一输入。 预测方程将允许使用基本土壤表征数据来确定开裂程度，而不是复杂的理论解。 研究结果将适用于在易开裂土壤上设计和建造工程结构以及建造废物容纳设施。 此外，结果将适用于地下水补给问题，污染物在包气带的运输，和农业问题。

This research focuses on desiccation cracking, and on the need to develop geometric information on crack geometry through the development of nondestructive testing techniques or application to fine grained soils that are susceptible to changes in properties including strength, volumetric relationships, and hydraulic properties. The objective of the proposed research is to develop an ultrasonic nondestructive testing technique to determine the depth of desiccation cracks in clay soils and to relate the depth of cracking to various clay properties. The investigators will formulate a series of predictive equations relating to the development and propagation of cracks, such as: depth of cracking, surface crack density, and rate of crack propagation as a function of plasticity and activity, mineralogy, initial water content, compaction conditions, and strength of soils, and wetting and drying cycles applied to the soils. The crack characteristics that will be analyzed experimentally include soil moisture suction corresponding to crack initiation, depth of propagation, surficial geometry, rate of crack propagation, and moisture flux through cracks, with a focus on the effects of cracking on hydraulic properties of the soils. The research will experimentally determine the modification of flow through the clay as a result of the presence of cracks. The ultrasonic method will provide an innovative tool to analyze the depth of cracking in soils, and will be used together with previously developed image analysis techniques to determine 3-D characteristics of cracks. These two methods can be applied to analyze tension cracks, freeze/thaw cracks, or any other type of crack developing in soils. The ultrasonic equipment can also be readily transported to the field for tests, and photographs of the desiccation process are the only input required for the image analysis. The predictive equations will allow for determining extent of cracking using basic soil characterization data as opposed to complicated theoretical solutions. Results of the research will apply to design and construction of engineering structures on soils susceptible to cracking and construction of waste containment facilities. In addition, the results will apply to groundwater recharge problems, contaminant transport in the vadose zone, and agricultural problems.