The paper presents a new single-surface elasto-plastic model for unsaturated cemented soils, formulated within the critical state soil mechanics framework, which should be considered as an extension to unsaturated conditions of a recently proposed constitutive law for saturated structured soils. The model has been developed with the main purpose of inspecting the mechanical instabilities induced in natural soils by bond degradation resulting from the accumulation of plastic strains and/or the changes in pore saturation. At this scope, the constitutive equations are used to simulate typical geotechnical testing conditions, whose results are then analysed in light of the controllability theory. The results of triaxial tests on an ideal fully saturated cemented soil and on the corresponding unsaturated uncemented one are first discussed, aiming at detecting the evidence of potentially unstable conditions throughout the numerical simulations. This is followed by similar analyses considering the combined effects of both the above features. For each analysed case, a simple analytical stability criterion is proposed and validated against the numerical results, generalizing the results, and highlighting the crucial role of state variables and model parameters on the possible occurrence of failure conditions.

本文提出了一种新的非饱和胶结土单面弹塑性模型，该模型在临界状态土力学框架内制定，应被视为对最近提出的饱和结构土本构定律的非饱和条件的扩展。开发该模型的主要目的是检查由塑性应变积累和/或孔隙饱和度变化引起的粘结退化在天然土壤中引起的机械不稳定性。在此范围内，本构方程用于模拟典型的岩土工程测试条件，然后根据可控性理论分析其结果。首先讨论了理想的完全饱和胶结土和相应的不饱和未胶结土的三轴试验结果，旨在检测整个数值模拟中潜在不稳定条件的证据。接下来是考虑到上述两个特征的综合影响的类似分析。对于每个分析案例，提出了一个简单的分析稳定性准则，并根据数值结果进行验证，概括了结果，并突出了状态变量和模型参数对可能发生的故障条件的关键作用。