通过广西地区红黏土和膨胀土的室内干湿循环模拟试验,探讨了干湿循环条件下胀缩性土的强度衰减规律;在此基础上,建立了黏聚力衰减率与循环次数的关系;根据黏聚力衰减曲线变化特征,提出采用S型曲线函数进行拟合,并与其他类似的试验结果进行了拟合效果验证。研究结果表明:①胀缩性土的黏聚力随干湿循环次数增加而衰减,最终趋于稳定;干湿循环次数引起内摩擦角的波动变化极小,基本保持一稳定值。②S型曲线函数能很好地描述土体强度干湿循环衰减规律,反映土体干湿循环达到一定次数后土体强度趋于稳定的规律,克服了以往线性函数、多项式函数和指数函数拟合存在的不足。 Through the indoor wetting and drying cycle simulation tests of red clay and expansive soil in Guangxi region, the law of strength attenuation of expansive soil under wetting and drying conditions was discussed. Based on this, the relationship between the decay rate of cohesion and the number of cycles was established. According to the change characteristics of the cohesion decay curve, the S-curve function is proposed to be fitted and the fitting effect is verified with other similar test results. The results show that: (1) The cohesion of the expansive soil decreases with the increase of the number of wet and dry cycles and eventually stabilizes. The variation of the internal friction angle caused by the number of wet and dry cycles has little change and basically maintains a stable value. ②S curve function can well describe the law of attenuation of wet and dry cycle of soil strength and reflect the law of soil strength tends to be stable after the soil wetting and drying cycle reaches a certain number of times, which overcomes the previous linear function, polynomial function and exponential function fitting There are deficiencies.