Cyclic and creep combination effects on the long-term undrained behavior of overconsolidated clay
Cyclic and creep combination effects on the long-term undrained behavior of overconsolidated clay
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DOI：
10.1007/s11440-020-01078-5
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发表时间：
2020-09
期刊：
影响因子：
5.7
通讯作者：
Jian Han;Z. Yin;C. Dano;P. Hicher
中科院分区：
文献类型：
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作者：
Jian Han;Z. Yin;C. Dano;P. Hicher
在不排水条件下，软土在循环荷载作用下，通常会表现出超孔压的增加，从而使土体处于超固结状态。然后，在随后的大量循环(例如，超过一百万次)下，也需要时间，超固结状态下的蠕变影响循环效应，从而导致复杂的长期不排水行为。本文旨在阐明超固结粘土的这种长期不排水特性。重组后的样品是从法国北部取回的自然样品中制备的。首先，确定了沿单调三轴应力路径的抗剪强度特征。然后对超固结试件在完全饱和和不排水条件下进行了荷载控制循环试验。施加小的循环偏应力是为了更详细地研究在非常大量的循环下的行为，在此期间观察到不寻常的孔压演变。为了解释这一点，在一定的应力状态下，对具有不同OCR值的重组试件进行了不排水三轴蠕变试验。讨论了不排水蠕变过程中轴向应变、超孔压、应力比、应力路径、塑性应变率和应力扩容的演化规律。不排水蠕变试验还表明，循环荷载引起的孔压增加和蠕变引起的孔压降低是两个相互竞争的过程。
Soft soil subjected to cyclic loading typically exhibits an increase in excess pore pressure under undrained condition which brings the soil to an overconsolidated state. Then, under a subsequent large number of cycles (e.g. more than one million) which also takes time, the creep at overconsolidated state influences the cyclic effect and thus results in a complicated long-term undrained behavior. This paper aims to clarify this long-term undrained behavior of overconsolidated clay. The reconstituted samples are prepared from natural samples retrieved in the north of France. First, the shear strength characteristics along monotonic triaxial stress paths are identified. Then load control cyclic tests on overconsolidated specimens are conducted in fully saturated and undrained conditions. Small cyclic deviatoric stresses are applied in order to investigate more particularly the behavior under a very large number of cycles, during which an unusual pore pressure evolution is observed. To explain this, undrained triaxial creep tests are performed on reconstituted specimens with different values of OCRs under some specified stress states. The evolutions of axial strain, excess pore pressure, stress ratio, stress path, plastic strain rates and stress dilatancy during undrained creep are discussed. The additional undrained creep tests also show that two processes are simultaneously acting in a competitive manner: increase in the pore pressure due to the cyclic loading and decrease in the pore pressure because of creep.