The uniaxial tensile strength (UTS) of soils is conventionally considered as a fraction of suction stress and suction stress is believed to be the product of matric suction and the kth power of effective saturation. The effective saturation is hard to be accurately determined while k, a parameter used to balance the surging matric suction as the soil dries, is rather ambiguous in its physical meaning. This study aims to develop an equation for describing the relationship among matric suction, unconfined compressive strength (UCS), and UTS. To this end, two stages of experiments involving unconfined compression test, uniaxial tensile test, and matric suction measurement test on expansive soils are performed on two batches of expansive soils. Results show that although no one-to-one relation could be found between UCS and UTS, there is a sound linear relationship between matric suction and the ratio of UCS to UTS. Based on this fact, a two-parameter equation correlating matric suction, UCS, and UTS, was established, and the physical meanings of both parameters are interpreted.

土壤的单轴抗拉强度 (UTS) 通常被认为是吸力应力的一部分，并且吸力应力被认为是基质吸力与有效饱和度的k次方的乘积。有效饱和度很难准确确定，而k作为土壤干燥时用于平衡基质吸力的参数，其物理意义相当模糊。本研究旨在建立一个方程来描述基质吸力、无侧限抗压强度 (UCS) 和 UTS 之间的关系。为此，对两批膨胀土进行了两阶段膨胀土无侧限压缩试验、单轴拉伸试验和膨胀土基质吸力测量试验。结果表明，虽然UCS和UTS之间没有发现一一对应的关系，但基质吸力与UCS与UTS的比值之间存在良好的线性关系。基于此，建立了基质吸力、UCS和UTS的双参数方程，并解释了这两个参数的物理意义。