Experimental Study on Shear Characteristics of Silt under Different Temperature-humidity Freeze-thaw Cycles
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摘要: 为了探究不同温湿条件下冻融循环作用对压实粉土剪切特性的影响，以郑州黄泛区粉土为研究对象，在−5~5 ℃和−15~15 ℃温度幅值冻融循环条件下，对含水率为6.0%、10.0%、14.0%、18.0%以及饱和含水率下的压实粉土试样进行冻融循环，并进行剪切特性试验及微观结构分析。结果表明：冻融循环过程中，压实粉土颗粒间的接触方式、排列组合和孔隙特征发生改变，抗剪强度呈先降低后逐渐趋于稳定趋势；由于土中水发生相变和颗粒间作用力发生变化，土样含水率越大，冻融温度幅值对土样剪切强度及其强度参数衰减作用越明显；相同温度幅值条件下，由于颗粒面胶结以及孔隙间水膜润滑的综合作用，冻融循环过程中压实粉土含水率越高，抗剪强度及黏聚力衰减比例越小，内摩擦角衰减比例越大。Abstract: To explore the influence of freeze-thaw cycles on the shear characteristics of compacted silt under different temperature and humidity conditions, the silt in the Yellow River flooding area of Zhengzhou was taken as the research object. Under the freeze-thaw cycles of -5°C to 5°C and -15°C to 15°C, the soil samples with water content of 6%, 10%, 14%, 18% and saturation moisture content were subjected to freeze-thaw cycles. The results show that during the freeze-thaw cycle, the contact mode, arrangement and pore characteristics of compacted silt particles change, and the shear strength first decreases and then tends to be stable. Due to the phase change of water in the soil and the change of the inter-particle force, the greater the moisture content of the soil sample, the more obvious the attenuation effect of the freeze-thaw temperature amplitude on the shear strength of the soil sample. Under the condition of the same temperature amplitude, due to the comprehensive effect of particle surface cementation and inter-pore water film lubrication, the higher the moisture content of the compacted silt, the smaller the attenuation ratio of shear strength and cohesion, and the greater the attenuation ratio of internal friction angle during the freeze-thaw cycle.
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表 1 土体基本物理性质参数
液限wL/% 塑限wP/% 塑性指数IP 颗粒比重GS 最优含水率wop/% 最大干密度 ρdmax/(g·cm−3) 土颗粒组含量占比/% >0.075 mm 0.075～0.005 mm <0.005 mm 26.76 17.50 9.26 2.69 14.0 1.78 8.63 78.93 12.44 
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