中文摘要：

针对目前土工单轴拉伸试验水平的不足,研制了一套新型土工单轴拉伸试验装置,该套装置主要由试样制备、加载、控制与数据采集4个部分组成。试验装置通过燕尾槽与双滑动底板的设计,可以制备不同拉伸段长度的试样并分别开展相应的单轴拉伸试验;通过试样形式与所对应拉伸夹具的设计,解决了试样端部在拉伸过程中出现的松弛与应力集中问题;通过双导轨拉伸装置的设计,避免了试样在拉伸过程中出现的应力偏心现象;通过双级变速箱的设计使最小拉伸速率可达到0.001 mm/min,能够准确描述材料单轴拉伸破坏的演化过程,并能准确测试材料的抗拉强度以及全过程的拉应力-位移关系曲线。基于所研制的试验装置开展了黏性土的单轴拉伸试验,试验结果表明：黏性土的单轴拉伸破坏形式不是纯脆性破坏,而是在抗拉强度后存在一个软化阶段,此时仍具有一定的承载能力;随着试样拉伸段长度的增大,抗拉强度呈对数减小,峰值位移呈对数增大;随着拉伸速率的增加,抗拉强度呈对数增加,峰值位移呈线性增加;抗拉强度与峰值位移均随压实度的递增呈线性增加;随着含水率的递增,试样的抗拉强度先增大后减小,即存在一个峰值,而峰值位移呈线性增加。

英文摘要：

Since the current device for geotechnical direct tension tests is limited, a new direct tension device was developed in this study. The testing device consists of four components： sample preparation, loading, control and data acquisition system. With the novel design of＂dovetail＂ groove and a double sliding plate on the device, direct tension tests can be conducted on prepared samples with different lengths. Due to the chosen sampling forms and their corresponding stretching fixture, the problems of relaxation and stress concentration on the ends of the specimen can be solved during the drawing process. The phenomenon of eccentric stress appearing in the drawing process can be avoided using the double rail stretching device. The minimum tensile rate of the device is 0.001 mm/min assisted by the two-stage gearbox design. Therefore, the device can be used to describe the evolution of uniaxial tensile failure and to determine tensile strength and tensile stress-displacement curve in the whole process. Direct tension tests were carried out on clay specimens using the developed device. The results show that the uniaxial tensile failure mode of clay is not purely brittle fracture, but there exists a softening stage after the tensile strength, and at this moment, clay specimens still have the certain bearing capacity. With the increase of the length of stretching section, the tensile strength decreases logarithmically while the peak displacement increases logarithmically. With the increase of tensile rate, tensile strength increases logarithmically while the peak displacement increases linearly. Both tensile strength and the peak displacement increase linearly with increasing compactness. With the growth of moisture content, tensile strength increases initially and decreases afterward, but the peak displacement linearly increases.