冻融循环作用下土石混合体水-热-变形相互作用过程研究

Study on water-heat-deformation interaction process of soil-rock mixtureexposed to freeze-thaw cycles

冻融循环作用显著影响土石混合体的水-热-变形相互作用过程及力学特性。基于此,本文开展了单向冻融循环作用下土石混合体水-热-变形相互作用及无侧限抗压强度试验。通过单向冻融循环装置对30%砾石含量的土石混合体进行了4次单向冻融循环试验,每次循环根据设定的温度变化曲线持续168小时,模拟实际自然环境中冻结和融化的周期。同时,利用微机控制电液伺服万能试验机开展了未冻融和冻融循环后试样的力学特性测试,并探讨了冻融循环对土石混合体微观结构劣化机理的影响。研究结果表明:单向冻融循环对试样内温度、水分和变形有显著影响。冻融循环过程中土石混合体的融化速率大于冻结速率,试样在冻融循环过程中存在着体积未冻水的迁移和重分布。第一次冻融循环对土石混合体变形影响最为显著,试样的净变形随着冻融循环次数的增加先增大后趋于稳定。此外,反复的单向冻融循环改变了试样的孔隙结构。冻融循环后试样的抗压强度和变形模量分别减小了45.31%和60.92%,其衰减幅值随着冻融循环次数的增加而降低。

Freeze-thaw cycles significantly affect the water-heat-deformation interaction process of the soil-rock mixture.Therefore,this paper carried out the water-heat-deformation interaction and unconfined compressive strength test of the soil-rock mixture under unidirectional freeze-thaw cycles.Utilizing a unidirectional freeze-thaw cycling device,the soil-rock mixture sample with a rock content of 30%was prepared,and four freeze-thaw cycles were conducted according to the preset temperature change curve,with each cycle lasting 168 hours.Simultaneously,the mechanical properties of the sample both before and after freeze-thaw cycles were conducted,and the microstructural deterioration mechanism of the soil-rock mixture exposed to freeze-thaw cy-cles was investigated.The results show that the unidirectional freeze-thaw cycle has a significant effect on the temperature,moisture,and deformation variations in the treated sample.In the process of unidirectional freeze-thaw cycles,the melting rate of the soil-rock mixture is greater than the freezing rate.Meanwhile,the frost depth changes continuously during the freeze-thaw cycles and does not reach a stable state within the limited number of freeze-thaw cycles.The migration and redistribution of volumetric unfrozen water in soil samples oc-curred during the freeze-thaw processes.At the onset of the experiments,the volumetric unfrozen water content changes under the influence of temperature gradients,causing the liquid water to infiltrate downwards and lead-ing to the accumulation of unfrozen water at the middle location of the sample,while the volumetric unfrozen water content at the top does not undergo drastic changes.Additionally,the first freeze-thaw cycle has a signifi-cant influence on the vertical deformation of the soil-rock mixture,and the net deformation of the sample increas-es first and then tends to be stable with the freeze-thaw cycles raised.Furthermore,the pore structure and inter-nal arrangement of the soil-rock mixture are restructured during the unidirectional freeze-thaw cycles.The repeat-ed expansion and contraction of soils accelerate the destruction of the skeletal structure,gradually reducing the attraction among soil particles and leading to the formation of new fractures.The unconfined compressive strength test shows that the compressive strength and deformation modulus of the sample decrease by 45.31%and 60.92%,respectively.