中文摘要：

膨胀土在干燥过程中由于失水收缩容易产生龟裂,裂隙产生后会极大削弱土体的工程性质。了解膨胀土在干燥过程中的抗拉强度特性,对从力学上进一步认识龟裂的形成和发展过程有重要意义。在室内配制了若干组初始饱和的膨胀土泥浆试样,当试样干燥到不同含水率时,利用改装的超微型贯入仪对试样开展了一系列抗拉试验,获得了膨胀土在干燥过程中抗拉强度与含水率的关系。此外,运用蒸汽平衡法对试样干燥过程中的吸力进行控制,研究了抗拉强度受吸力的影响。结果表明：在干燥过程中,试样的抗拉强度随含水率的减小呈指数形式增加。在含水率小于塑限（40%）之前,抗拉强度较小,增幅不明显;当含水率达到塑限之后,抗拉强度随着含水率的减小增加较快。在控制吸力条件小,试样含水率随吸力的增加呈指数减小,抗拉强度与吸力呈线性正相关关系。通过分析发现,土中水的存在形式、水-土相互作用、颗粒间接触状态以及土体结构的变化是导致土体抗拉强度在干燥过程中增加的主要原因。

英文摘要：

Upon drying,desiccation cracks would occur in expansive soils due to evaporation and volume shrinkage.The presence of cracks may significantly weaken soil engineering properties.Better understanding the characteristics of tensile strength during drying is very helpful to study the essential mechanisms of desiccation crack initiation and propagation.In this investigation,Romainville expansive soil was used and several groups of initially saturated slurry specimens were prepared.The specimens were then dried in room condition to different water content.Direct tensile test was performed on these specimens by employing the modified super mini-penetrometer（SMP-1）.The evolution of tensile strength with water content was quantitatively characterized.In addition,vapor equilibrium technique was applied to control the soil suction during drying,and the effect of suction on tensile strength was also studied.The results indicate that,during drying,the specimen tensile strength generally increases exponentially with decreasing water content.Before the water content is lower than plastic limit（40%）,the tensile strength and the increase rate is very low;after the water content reaches the plastic limit,a slight decrease of water content can lead to significant increase of the tensile strength.With increasing suction,the specimen water content decreases exponentially as expected,and the tensile strength increases linearly.It is found that the evolution behaviour of soil tensile strength during drying is mainly connected with pore water properties,water-soil interactions,contact behviour between soil particles and soil structure.