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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。
Aiming at the deficiency of the present geotechnical uniaxial tension test, a new set of geotextile uniaxial tension test device has been developed. The device mainly consists of sample preparation, loading, control and data acquisition. Through the design of the dovetail groove and the double sliding floor, the test device can prepare the specimens with different stretch lengths and carry out the corresponding uniaxial tensile tests respectively. Through the design of the specimen forms and the corresponding stretching clamps, the specimens The end of the tension in the process of relaxation and stress concentration problems; through the double rail drawing device design to avoid the sample during the stress of stress in the process of eccentric phenomenon; through the design of two-stage gearbox minimum stretch The rate can reach 0.001 mm / min, which can accurately describe the evolution process of uniaxial tensile failure and can accurately test the tensile strength of the material and the whole process of tensile stress - displacement curve. The uniaxial tensile test of cohesive soil was carried out based on the developed test device. The experimental results show that the uniaxial tensile failure mode of cohesive soil is not pure brittle failure, but exists a softening stage after tensile strength, When the length of the specimen increases, the tensile strength decreases logarithmically and the peak displacement increases logarithmically. With the increase of the tensile rate, the tensile strength is equal to And the peak displacement increases linearly. The tensile strength and peak displacement increase linearly with the increasing of compaction degree. With the increase of water content, the tensile strength of the sample first increases and then decreases, that is, there is a peak value , While the peak shift increases linearly.