冰水赋存演化下冻结土石混合体-结构界面强度劣化机制及模型

Strength deterioration mechanism and model of interface between frozen soil-rock mixtures and structures under ice water occurrence and evolution

温升下冻结土石混合体-结构界面层孔隙内冰水赋存改变极易诱发强度劣化,而目前界面强度劣化机制及劣化规律定量表征的相关研究存在空白。制备0%,15%,30%,45%等4种含石率组合体试样,通过核磁共振、直剪试验研究了正融过程冰水赋存演化下界面强度劣化特性,结合莫尔-库仑准则首次提出以薄膜水及毛细水含量变化率为参变量的强度劣化模型。得到结论:含石改变界面孔隙结构分布使毛细水占比升高;温升下界面抗剪强度劣化程度随含石率增加而降低;正融后不同含石率界面黏聚力衰减程度均大于内摩擦角衰减程度;黏聚力、内摩擦角与未冻水含量关系曲线分别呈阶段非线性特点及两阶段线性特点,其实质在于薄膜水及毛细水发育使得界面黏聚力和内摩擦角产生不同程度及形式的劣化。模型分析表明:随含石率升高,薄膜水及毛细水劣化系数具有“此消彼长”的特性,颗粒间及颗粒与结构接触面滑动摩擦强度和咬合摩擦强度劣化比例系数分别呈现下降、上升趋势。

The ice-water transitions in the pores of the interface layer between frozen soil-rock mixtures can easily induce strength degradation under temperature rise.However,there is a gap in the current researches on the mechanism and quantitative characterization of interface strength degradation.The degradation of interfacial strength under ice-water evolution in the melting process is therefore studied by the testing samples with rock contents of 0%,15%,30%and 45%using the nuclear magnetic resonance and direct shear tests.The strength degradation model considering the change rates of membrane water and capillary water is proposed for the first time combining with the Mohr-Coulomb criterion.The results indicate that the unfrozen capillary water increases with rock content due to the change of pore structures at the interface;the degradation degree of interfacial strength under temperature rise decreases with the increasing rock content.The attenuation of interfacial cohesion is greater than that of internal friction angle after melting.The relations between cohesion and internal friction angle with unfrozen water content are nonlinear and staged linear,respectively,because the interfacial cohesion and internal friction angle deteriorate differently with changing film water and capillary water.With the increasing rock content,the deterioration coefficients of film water and capillary water exhibit the trend of"one decreases and the other increases",and the deterioration coefficients of sliding and interlocking friction strengths show downward and upward trends respectively for both the particles and the particle-structure interface.