中文摘要：

在干燥环境中,由于蒸发失水,膨胀土发生收缩,表面容易产生纵横交错的裂隙网络（龟裂）。龟裂的产生会极大弱化土体的工程性质,并导致各种工程问题。随着极端干旱气候的频发,膨胀土龟裂问题将会越来越多,越来越显著。开展龟裂研究对揭示龟裂现象的本质规律和指导膨胀土地区的工程实践有重要意义。龟裂的形成和发展是一个动态的过程,与土中水分的蒸发速率、应力状态、收缩特性等直接相关：龟裂形成时水分蒸发处于常速率阶段;吸力和抗拉强度是制约龟裂形成的两个关键力学参数,当土体中的吸力引起的张拉应力超过土体的抗拉强度时,龟裂便会产生;龟裂是孔隙发生收缩的直观表现。总体上,力的作用和收缩空间是土体龟裂形成的两个必要条件。此外,膨胀土龟裂具有非常复杂的发生发展过程,受土质学、土力学、土结构、试验条件和方法等许多因素的影响。龟裂定量分析是龟裂研究的重要内容之一,能为龟裂机理研究及相关理论模型的建立提供必要参数。计算机图形处理技术具有效率高、操作性强、精度高等优点,为龟裂定量分析提供了强有力的工具。目前关于土体龟裂研究还存在许多不足之处,在今后的工作中,应该重视龟裂形成和发展过程的动态特征,围绕与土体龟裂相关的水-土作用关系、力学机制、收缩变形机制、大尺度现场试验和三维观测分析技术等方面开展更多的针对性研究,综合考虑龟裂形成过程中的土质学、土力学和土结构因素,结合宏观现象与微观分析,建立土体龟裂的理论体系。

英文摘要：

Upon drying, the evaporation of soil water results in volumetric shrinkage and desiccation cracks on ex pansive soils. The presence of crack can significantly weaken the engineering properties of soil, and cause various problems in geological, geoteehnical, hydraulic, environmental engineering fields. With the increasing frequency of severe drought climate, the engineering problems that induced by desiccation cracking can be more and more, worse and worse. The study of desiccation cracking is therefore very significant for revealing the intrinsic mecha nisms behind this common natural phenomenon, and plays an important role in engineering practice in clayey soil areas and especially in expansive soil areas. Generally, the initiation and propagation of desiccation cracks show evident dynamic characteristics and significantly depend on soil water evaporation rate, stress state and shrinkage property. The cracks initiate at constant evaporation rate stage. Soil suction and tensile strength are the two key me chanical parameters that control the cracking behavior. Cracking is likely to occur if the tensile stress which is induced by soil suction reaches the tensile strength of soil. Intrinsically, cracking is the result of pore shrinkage, h is believed that the mechanical effect and shrinkage potential are the two necessary factors for crack initiation. It is found that the desiccation cracking behaviour is affected by many factors including soil materials, mechanical prop erties, structures, test conditions, and test methods. Quantitative characterization of crack patterns is required for desiccation cracking investigation, and plays very, important role in understanding the cracking mechanism and con the relevant model. Image processing is a powerft,l, efficient and highaccurate tool for quantitative de scription crack patterns. In the next stage, more attention shouht be paid to the dynamic characteristics of crack ing, and more work should be done on watersoil interaction, mechanical mechanism, shrinkage mechani