This paper describes the development of a direct tension apparatus and its application to test the tensile strength of unsaturated fine sands. The apparatus consists of two halves of wedge-shaped specimen molds. A criterion is developed for designing the inclination angle of the inner sidewall of the specimen molds as a function of soil–wall interface frictional angle and soil dilatancy angle. Tensile strength of unsaturated fine sands is measured over a range of dry density and water content. Results show that tensile strength generally increases with the increase in dry density. For relatively dense sand, tensile strength follows a non-monotonic double-peak pattern with increasing water content. The first peak occurs in the pendular regime and is attributed to peak occurrence of interparticle stress contributed by pendular water bridges. The second peak occurs in the capillary regime and is attributed to the capillary component of interparticle stress arising from negative pore pressure.

中文翻译：

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非饱和细砂抗张强度试验研究

本文介绍了直接张紧装置的发展及其在测试不饱和细砂抗张强度方面的应用。该设备由两半楔形样品模具组成。制定了一个标准来设计样品模具内侧壁的倾角，该倾角是土-墙界面摩擦角和土膨胀角的函数。在一定的干密度和水含量范围内测量不饱和细砂的拉伸强度。结果表明，拉伸强度通常随干密度的增加而增加。对于相对致密的沙子，抗张强度遵循非单调双峰模式，且含水量增加。第一个峰值出现在摆动状态，并归因于由摆动水桥引起的粒子间应力的峰值出现。