Recent laboratory investigations conducted on soils prone to mud pumping have shown that the subgrade soil experiences softening associated with an internal redistribution of moisture when the cyclic stress ratio (CSR) exceeds a certain critical level. This article aims to evaluate the stiffness degradation of these problematic subgrade soils subjected to a wide range of loading conditions. The test results revealed that the instability of the specimens is caused by the early softening behaviour, and this is accompanied by a sharp reduction in the specimen stiffness. As high as 70–80% reduction in the initial small-strain stiffness was observed even for densely compacted specimens (ρ_d = 1790 kg/m³). In this regard, a new method for predicting the threshold number of cycles, N_thr and residual axial strains required for the onset of subgrade instability is proposed. As a useful practical guide, a quasi-linear relationship between the threshold strain and N_thr is also determined.

最近对易于抽泥的土壤进行的实验室研究表明，当循环应力比（CSR）超过某个临界水平时，路基土壤会发生软化，并伴随水分的内部重新分布。本文旨在评估在各种载荷条件下这些有问题的路基土的刚度退化。测试结果表明，试样的不稳定性是由早期的软化行为引起的，并且伴有试样刚度的急剧降低。高达在初始小应变减少70-80％的，甚至观察到密集压实试样（ρ _d  =1790公斤/米³）。在这方面，提出了一种新的方法，用于预测路基失稳开始所需的阈值循环数，N _thr和残余轴向应变。作为有用的实用指南，还确定了阈值应变和N _thr之间的准线性关系。