This paper presents a series of experimental studies for evaluating the effects of closed-system freeze–thaw (FT) cycles on the hydro-mechanical behaviours of two subgrade soils (a low plastic lean clay, SS and a lean clay with higher plasticity, HC). Investigated hydro-mechanical behaviours include the soil–water characteristic curve (SWCC) obtained from the filter paper method, resilient modulus (M_R) determined from cyclic triaxial tests, unconfined compression strength (q_u) and reloading tangent modulus (E_1%) and stress (S_u1%) at 1% strain measured from unconfined compression tests, with emphasis on the SWCC and M_R. Specimens compacted at the maximum dry density (ρ_dmax) and optimum moisture content (w_opt) were firstly subjected to multiple FT cycles (number of FT cycles N_FT = 0, 1, 3, 6 and 10) and then dried or wetted to different moisture contents before determining hydro-mechanical behaviours. Experimental results revealed that (i) FT cycles reduce the magnitude of volumetric strain upon moisture variation for the HC but have little impact on the SS; (ii) FT cycles reduce the water retention capacity of both soils. For each soil, the void ratio (e)-moisture content (w)-suction (s) relationships after different FT cycles are possibly distributed on a unique surface; (iii) Reductions in the mechanical properties (i.e. M_R, q_u, E_1% and S_u1%) are more significant at N_FT = 1 and vary with the post-FT cycle moisture content. Reductions in the M_R are most serious at a threshold w level on the wet side of w_opt; (iv) FT cycles reduce the sensitivity of the mechanical properties to moisture content for the HC but exert minor influence on that of the SS; (v) Relationships of the M_R to the q_u, E_1% and S_u1% are not influenced by the N_FT and moisture content for both soils. They are non-linear and can be well described by quadratic polynomials. Soils with higher plasticity such as the HC is, in general, more vulnerable to effects of closed-system FT cycles at w_opt than low plastic soils such as the SS.

本文提出了一系列实验研究，以评估封闭系统冻融（FT）循环对两种路基土壤（低塑性贫粘土SS和高塑性可塑性HC）的水力力学行为的影响。 ）。研究的流体力学行为包括通过滤纸法获得的土壤-水特征曲线（SWCC），通过循环三轴试验确定的弹性模量（M _R），无侧限抗压强度（q _u）和重载切线模量（E _1％）通过无边压缩测试测得的应变为1％时的应力和应力（S _u1％），重点是SWCC和M _R。在最大干密度压实试样（ρ _DMAX）和最佳的水分含量（瓦特_选择）为首次进行多个FT周期（FT周期N中的数_FT  = 0，1，3，6和10），然后进行干燥或润湿在确定水力机械性能之前，先确定不同的水分含量。实验结果表明：（i）FT循环可降低HC水分变化引起的体积应变的幅度，但对SS的影响很小；（ii）FT循环会降低两种土壤的保水能力。对于每种土壤，孔隙率（e）-水分含量（w）-吸力（s）不同FT循环后的关系可能分布在唯一的表面上；（iii）在N _FT  = 1时，机械性能（即M _R，q _u，E _1％和S _u1％）的降低更为显着，并且随FT循环后水分含量的变化而变化。在w _opt的湿端，在阈值w处，M _R的降低最为严重；（iv）FT循环降低了HC的机械性能对水分含量的敏感性，但对SS的影响很小；（v）M _R与q的关系_u，E _1％和S _u1％不受两种土壤的N _FT和水分含量的影响。它们是非线性的，可以用二次多项式很好地描述。土具有较高的可塑性，如HC，在一般情况下，在更容易受到封闭系统FT周期的影响瓦特_选择比低的塑料的土壤如SS。