| 摘要: |
| 【目的】对非饱和原状黄土经历冻融循环后强度的变化规律进行研究，为分析黄土地区冻融病害机理提供参考。【方法】制备含水率分别为16.5%，20.5%，24.0%，29.0%和32.5%的非饱和原状黄土，采用可设定温度的冰柜冻结及室外融化的方法进行冻融循环处理，冻结温度分别为－8，－13，－21 ℃，冻融循环次数分别为1，3，5，7次，然后对冻融循环后的土样进行直剪试验，得到受冻融循环影响的土体抗剪强度参数，分析冻融循环次数、含水率、冻结温度对黏聚力和内摩擦角的影响规律。基于-21 ℃下黏聚力随冻融循环次数变化的数据，拟合得到黏聚力劣化模型表达式。【结果】在16.5%，20.5%，24.0%，29.0%和32.5%含水率下，－21 ℃冻融循环7次之后土样黏聚力分别由24.50，18.52，12.69，9.56和7.56 kPa降低到21.04，13.52，7.45，2.60和0.23 kPa，含水率32.5%的原状土样黏聚力减小量最大。同一含水率下黏聚力随冻融循环次数的增加呈指数减小，随着冻结温度的降低，黏聚力变化并不明显。内摩擦角在冻融循环后增加量为1°～2°。拟合得到了非饱和原状黄土黏聚力劣化模型表达式，其拟合结果与实测结果的相关系数均在0.937以上，计算值与实测值基本吻合，拟合度较高。【结论】同一含水率下原状黄土黏聚力随冻融次数的增加呈指数减小。冻结温度对不同含水率原状土样冻融后黏聚力与内摩擦角的影响不显著。 |
| 关键词: 黄土 冻融循环 抗剪强度 黄土劣化 |
| DOI： |
| 分类号: |
| 基金项目:国家自然科学基金项目（51078309；51208409）；陕西省教育厅专项科研计划项目（12JK0914） |
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| Freezing-thawing strength of unsaturated undisturbed loess |
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ZHANG Hui,WANG Tie-hang,LUO Yang
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| Abstract: |
| 【Objective】Variations in strength of unsaturated undisturbed loess during freezing-thawing cycles were investigated to analyze the freezing-thawing damage mechanism in loess area. 【Method】Unsaturated undisturbed loess samples with water contents of 16.5%,20.5%,24.0%,29.0% and 32.5% were prepared,respectively.Freezing-thawing cycle was simulated using freezer with temperatures of －8,－13,and －21 ℃ and outdoor melting.The numbers of freezing-thawing cycles were 1,3,5,and 7,respectively.Then the soil shear strength parameters influenced by freezing-thawing cycles were observed through the direct shear test of unsaturated undisturbed loess.The influence of freezing thawing cycle,water content,and freezing temperature on strength parameters was analyzed and the degradation model of cohesion was obtained by fitting data at -21 ℃.【Result】After seven freezing thawing cycles at -21 ℃,cohesion values of soil samples with water contents of 16.5%,20.5%,24.0%,29.0% and 32.5% decreased from 24.50,18.52,12.69,9.56,and 7.56 kPa to 21.04,13.52,7.45,2.60,and 0.23 kPa,respectively.Cohesion of undisturbed soil sample with water content of 32.5% reduced the most.Cohesion exponentially decreased with the increase of the number of freezing-thawing cycles at the same water content,while it did not change significantly with the decrease of freezing temperature.Angle of internal friction was increased by 1°-2° after freezing thawing cycles.The cohesive deterioration model of unsaturated undisturbed loess was obtained with the coefficients of >0.937.The calculated values were consistent with the measured values.【Conclusion】Cohesion exponentially decreased with the increase of number of freezing-thawing cycles at the same water content.The freezing temperature had no significant impact on cohesion and internal friction angle of the undisturbed soil samples. |
| Key words: loess freezing thawing cycles shear strength loess deterioration |
