本文提出了极限特性指标的概念。通过实验,取得了两个极端含水条件下的胀缩指标值。从数理分析的角度,论证了在现有实验边界条件下,土的胀、缩可逆关系,并建立了各极限特性指标的相关公式。最后,对极限特性指标应用的可能性提出了看法。 This article proposes the concept of limit characteristic indicators. Through the experiment, the index values ​​of swell and shrink under two extreme water conditions were obtained. From the point of view of mathematical analysis, it is demonstrated that under the existing experimental boundary conditions, soil swelling and contraction reversible relations, and established the correlation formula of each limit characteristic index. Finally, it gives opinions on the possibility of applying the limit characteristic indicators.