Abstract The impact of freeze-thaw cycling on freshly exposed loess is a major concern in design and construction of embankments or earth dams in the Loess Plateau in China. Due to complex nature of loess as compared with the conventional soils such as sand or clay, characterizing the strength of loess to account for this impact is challenging, in particular in the field conditions. In previous research a systematic approach in this regard is still lacking. This paper presents an investigation into the problem through well-controlled experiments using a pair of bender/extender elements. The shear wave (S-wave) velocities and the compression wave (P-wave) velocities were both measured on loess specimens subjected to freeze-thaw cycling. Under otherwise similar conditions, the unconfined compression tests were carried out to evaluate the soil strength of original loess and those with different fractions of add-in quartz sands. Several influence factors including the numbers of freeze and thaw cycles, the sand content and the water content were analyzed in a collective manner to characterize the changes of the unconfined compressive strength (UCS) of loess and the associated wave velocities. It was found that as the number of freeze-thaw cycles increases, the wave velocities of loess decrease. A clear difference in the magnitude of wave velocity was observed in the original loess samples due to the freeze-thaw cycling, whereas the discrepancies were less evident for the loess with higher sand contents. Based on the test results, exponential relationships were established respectively for the S wave and P wave velocities against the UCS values of the tested materials. Discussions were highlighted on whether the wave velocity can be used as an indicator to evaluate the UCS value of loess.

中文翻译：

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冻融循环作用下砂质黄土土体强度与波速的关系

摘要 冻融循环对新出露黄土的影响是我国黄土高原堤防或土坝设计和施工的主要问题。由于与传统土壤（例如沙子或粘土）相比，黄土具有复杂的性质，因此表征黄土强度以应对这种影响具有挑战性，尤其是在野外条件下。在以往的研究中，仍然缺乏这方面的系统方法。本文通过使用一对弯曲器/扩展器元件的良好控制实验对问题进行了调查。剪切波 (S 波) 速度和压缩波 (P 波) 速度均在经受冻融循环的黄土标本上测量。在其他类似的条件下，进行了无侧限压缩试验，评估了原始黄土和不同比例添加石英砂的土壤强度。综合分析冻融循环次数、含砂量和含水量等几个影响因素，表征黄土的无侧限抗压强度（UCS）和相关波速的变化。发现随着冻融循环次数的增加，黄土的波速减小。由于冻融循环，在原始黄土样品中观察到波速大小的明显差异，而对于含砂量较高的黄土，差异不太明显。根据测试结果，S波和P波速度分别与被测材料的UCS值建立了指数关系。重点讨论了波速是否可以作为评估黄土UCS值的指标。