【摘要】 为探究青藏高原冰碛土在冻融循环过程下的强度劣化规律与微观机制，采用室内试验与数值分析相结合的方法，通过开展标准三轴试验、扫描电镜实验及核磁共振实验，系统研究了不同初始条件（含水率、冻融循环次数）下冰碛土强度劣化特性和微观结构演变，并借助回归分析方法，建立了宏观强度参数与冻融作用之间的量化关系。结果表明：1）冻融循环后冰碛土的应力-应变关系曲线呈应变软化趋势，弹性模量与抗剪强度均随冻融次数增加而下降。在冻融循环前期（0～5次），弹性模量与抗剪强度的平均损伤率分别增至16.60%和10.33%，此时强度劣化最为明显；而在冻融循环后期（10～20次），强度特征参数呈小幅波动状态并趋于平稳。黏聚力与冻融循环次数呈负指数关系，而内摩擦角受其影响较小，仅表现为小幅波动。2）随冻融循环次数增加，冰碛土颗粒排列从密集、有序向松散、无序状态转变，孔隙结构发生明显变化。3）随冻融循环次数增加，细、微孔隙在水-冰相变过程产生冻胀力的作用下逐渐扩张并合并，形成大、中孔隙；冻融循环次数为20时，大、中孔隙占比上升至59.55%，细、微孔隙占比减少至40.45%，且孔隙结构调整在冻融后期（10～20次）已基本趋于稳定。基于此，本研究改进了适用于冰碛土在冻融循环下的莫尔库伦强度准则，并建立了抗剪强度、弹性模量与冻融循环次数的多参数耦合模型。更多还原

【Abstract】 In order to clarify the strength deterioration characteristics and microscopic mechanism of Qinghai-Xizang Plateau moraines during freeze-thaw cycles,laboratory tests(standard triaxial,scanning electron microscopy and nuclear magnetic resonance tests)and numerical regression methods were used to study the moraines under different initial conditions(water content and freeze-thaw cycles).A quantitative relationship between macroscopic strength parameters and freeze-thaw action was established through regression analysis.The research results show that:1)The stress-strain curve of the moraines after the freeze-thaw cycle exhibited a strain softening trend,with both elastic modulus and shear strength showing a downward trend,in the early freeze-thaw cycle(0-5 times)damage by about16.60% and 10.33% respectively,strength degradation is most obvious,and later in the freeze-thaw cycle(10-20 times)a slight fluctuations and steady state.Freezing and thawing cycles and cohesion of negative exponent,internal friction angle with the increase of freeze-thaw cycles was fluctuated,extends the applicable under the ice moraine soil freezing and thawing cycle of Mohr coulomb strength criterion,and established the shear strength,elastic modulus and multi-parameter coupling mathematical model of freeze-thaw cycles.2)SEM images showed that with the increase of freeze-thaw cycles,the arrangement of moraine particles changed from dense and ordered to loose and disordered.And the pore characteristic structure changes.3)NMR results demonstrated evolution characteristics in the internal pore structure of moraines under the freeze-thaw cycle.With deepening freeze-thaw cycles,large,medium pore proportion increased to 59.55%(N=20)micro,small pore proportion reduced to 40.45%(N=20).The small and small pores gradually expanded and merged under the action of frost heave force generated during the water-ice phase transition.Large and medium pores were formed,and the characteristic evolution process of pore structure was basically completed in the late freeze-thaw period(10-20 times).更多还原