循环荷载长期作用特征直接影响着粉质黏土的动力变形特性及土体结构的稳定性。运用SDT-10型动三轴仪对饱和粉质黏土进行高达20 000次的循环振动,分别控制固结围压、动应力比和振动频率,研究不同荷载条件下粉质黏土的塑性应变、残余孔压特性。研究结果表明:3项荷载条件都对土体的累计塑性变形和残余孔压有至关重要的影响。累计塑性应变在动力荷载持续作用下不断累积,曲线呈现出S型和J型,运用改进的种群增长模型以及改进的指数模型分别能很好拟合累计塑性应变随振动次数的发展规律,随围压、动应力比的增长呈正相关变化,随频率的增加呈反比下降。残余孔压比在正弦波的振动下不断增大,运用改进Seed孔压模型能在一定程度上模拟残余孔压变化规律,随动应力比、频率的增加而增大,随围压的增加而减小。研究成果深化了动力条件下黏土变形特性的认识,为循环荷载长期作用下土体的强度衰减和变形预测提供借鉴和参考。
Abstract
The dynamic characteristics of silty clay and the stability of soil structure are directly affected by long-term dynamic loading. The plastic strain and residual pore pressure of silty clay under different loading conditions are examined by controlling consolidation confining pressure, dynamic stress ratio and vibration frequency under 20 000 cyclic vibrations on SDT-10 dynamic triaxial apparatus. Results show that the cumulative plastic strain and residue pore pressure are significantly affected by three load conditions. Cumulative plastic strain accumulates under continuous dynamic loading, and the curve displays S-shape and J-shape. The improved population growth model and the improved exponential model could well fit the changes of cumulative plastic strain against vibration number: cumulative plastic strain changes in a positive relationship with the growth of confining pressure and dynamic stress ratio, but is inversely proportional to the increase of frequency. Residual pore pressure ratio increases continuously under the vibration of sine wave. The improved Seed pore pressure model could, to a certain degree,simulate the change rule of residual pore pressure ratio, which increases with the growth of dynamic stress ratio and frequency, while decreases with the climbing of confining pressure.The research results enriched our understanding on clayey soil deformation under dynamic conditions, and offered reference for predicting the strength decay and deformation of soil under long-term cyclic loading.
关键词
粉质黏土 /
动力特性 /
动三轴试验 /
塑性应变 /
残余孔压比
Key words
silty clay /
dynamic characteristic /
dynamic triaxial test /
plastic strain /
residual pore pressure ratio
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基金
国家自然科学基金项目(51409149);三峡库区地质灾害教育部重点实验室开放基金项目(2017KDZ05)
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