Cyclic loading and unloading true triaxial tests on remolded loess
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摘要: 针对不同应力路径往返加卸载条件下黄土累积塑性应变发展特性，以重塑黄土为研究对象，利用真三轴仪开展不同应力路径的往返加卸载试验研究，探究不同应力路径、应力幅值下黄土的循环应力时程曲线、滞回曲线、骨干曲线及累积塑性应变曲线的影响规律。揭示了应力路径对重塑黄土力学特性的影响，描述了各主应力与中主应力比b和应力幅值的相关性，提出了重塑黄土的滞回曲线近似呈椭圆形，长轴斜率随中主应力比b值的增大而增大，随应力幅值的增大而减小；随着中主应力比b值的增大，循环应力-应变骨干曲线随之硬化，累积塑性应变曲线依次降低，且累积塑性应变发展更早的进入平缓阶段，为解决相关黄土工程问题提供了参考。Abstract: Aiming at the development characteristics of cumulative plastic strain of loess under different stress paths under cyclic loading and unloading conditions, the remolded loess is taken as the research object, and the round-trip loading and unloading tests under different stress paths are conducted using a true triaxial apparatus to explore the influences of different stress paths and amplitudes on the cyclic stress time-history curve, hysteresis curve, backbone curve and cumulative plastic strain curve of loess. The results reveal the effects of the stress paths on the mechanical properties of the remolded loess, describe the correlation among each principal stress, ratio of the intermediate principal stress and the stress amplitude, and the hysteresis curve of the remolded loess is proposed to be approximately elliptical, with the slope of the major axis increasing with the increase of the ratio of the principal stress and decreasing with the increase of the stress amplitude. As the value of the ratio of the principal stress ratio increase, the backbone curve of cyclic stress-strain hardens accordingly, the cumulative plastic strain curve decreases in sequence, and the cumulative plastic strain develops earlier and enters a gentle stage. The research results provide a reference for solving the relevant problems in loess engineering.
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图 4 不同中主应力比b下土体滞回曲线
Figure 4. Hysteresis curves of different rations of intermediate principal stress
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图 6 不同应力路径下重塑黄土骨干曲线
Figure 6. Backbone curves of remolded loess under different stress paths
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图 7 不同应力路径下累积塑性应变与循环次数关系曲线
Figure 7. Relationship curves between cumulative plastic strain and cycle times under different stress paths
表 1 土的主要物理性质参数
Table 1 Physical parameters of specimens
相对质量密度Gs 干密度ρd/
(g·cm-3)天然含水率w/% 液限
wL/%塑限
wP/%塑性指数IP 2.70 1.40 21.00 34.20 18.60 15.60 
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表 2 真三轴试验方案
Table 2 True triaxial test schemes
固结围压σ3/kPa 应力幅值σm /kPa 中主应力比b 200 60，80，100，120 0，0.5，1 300 90，120，150，180 0，0.5，1
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