Strength characteristics of the melting silty clay under cyclic loading and the evolution law of hysteresis loop
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摘要: 季冻区路基春融过程中，特别是反复循环荷载作用下，极易造成承载能力显著降低、翻浆冒泥等灾害现象，但是目前对季冻区路基的研究大多数都停留在冻结土和经历冻融循环后全融土阶段，正融土的研究比较少。本文对正融粉质黏土进行了不同融化温度、冻结负温、含水率以及围压下的三轴单调加载和循环加卸载试验，研究发现经历循环加卸载的试样强度较单调加载绝大多数均有降低，每次循环会对试样造成一定的损伤；峰值强度随含水率的增大、围压减小而下降显著，主要由于试样顶端融化时存在大量水分和围压的约束作用造成；冻结负温和融化温度影响了融化速率，温度越低，前期强度越高，随时间推移影响减弱；用滞回环回弹模量定义了损伤变量，发现损伤变量与循环次数呈正相关；不同因素影响下，损伤变量的增长区别在于损伤快速发展和缓慢发展时对应循环次数上的差异；基于滞回环面积定义了耗散能，而损伤变量与耗散能却存在一定此消彼长的相关性。Abstract: In seasonal frozen subgrade in the process of melting in spring, especially under the again and again action of cyclic loading, it is easy to cause the mud pumping capacity to significantly reduce to result in disasters phenomena. Current researches of seasonal frozen subgrade mostly stay in the frozen soil and soil after freezing and thawing cycle melt phase, and little is known about the melting soil. In this paper, triaxial monotonic loading and cyclic loading and unloading tests are carried out on the melting silty clay under different melting temperatures, negative freezing temperatures, water content and confining pressures. It is found that the strength of the samples under cyclic loading and unloading is lower than that of most samples under monotone loading, and each cycle will cause certain damage to the samples. Because there is a large amount of water and confining pressure during melting, the peak strength of the sample decreases with the increasing water content and the decreasing confining pressure. The negative temperature of freezing and melting temperature affect the melting rate. The lower the temperature, the higher the strength in the early stage and the weaker the influence with time. The damage variables are defined by the rebound modulus of the hysteresis ring. Under the influence of different factors, the difference in the growth of damage variables lies in the difference in the corresponding cycle times when damage develops rapidly and slowly. Dissipative energy is defined based on the area of hysteresis ring, but there is a negative correlation between the damage variable and dissipative energy.
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Key words:
- melting soil /
- cyclic load /
- hysteresis loop /
- damage variable /
- dissipation energy
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