Abstract In this work, cyclic free swelling/shrinkage tests were conducted on uniaxial compacted GMZ bentonite specimens with consideration of influences of initial dry density and suction. For conducting the cyclic swelling/shrinkage test, vapour equilibrium technique was employed for suction control and a laser displacement sensor was adopted to measure the specimen dimension. Results reveal that influence of initial dry density on water retention property depends on suction. For suctions lower than 14.2 MPa, specimen with higher initial dry density exhibits stronger water retention capacity, while for suctions higher than 38 MPa, initial dry density hardly influences water retention property. Unrecoverable swelling or shrinkage volumetric deformation is accumulated during the cyclic suction-variation processes and influenced by initial suction of the specimen. Meanwhile, GMZ bentonite specimen tested exhibits a significant anisotropy on volume change, which is more distinct for specimens with higher initial dry density, with swelling anisotropy stronger than shrinkage one. For specimen with high suctions (≥3.3 MPa), suction variation along a single wetting or drying path hardly influence this volumetric anisotropy. However, swelling anisotropy decreases with increasing suction cycles experienced and eventually equals to the shrinkage one after several suction cycles.

中文翻译：

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自由膨胀条件下单轴压实GMZ膨润土的各向异性体积变化行为

摘要 在这项工作中，考虑初始干密度和吸力的影响，对单轴压实的GMZ膨润土试样进行了循环自由膨胀/收缩试验。为了进行循环膨胀/收缩试验，采用蒸汽平衡技术进行吸力控制，并采用激光位移传感器测量试样尺寸。结果表明，初始干密度对保水性能的影响取决于吸力。吸力小于14.2 MPa时，初始干密度较高的试样表现出更强的保水能力，而吸力大于38 MPa时，初始干密度几乎不影响保水性能。在循环吸力变化过程中积累了不可恢复的膨胀或收缩体积变形，并受试件初始吸力的影响。同时，测试的 GMZ 膨润土试样在体积变化方面表现出显着的各向异性，对于具有较高初始干密度的试样，这一点更为明显，膨胀各向异性强于收缩各向异性。对于具有高吸力 (≥3.3 MPa) 的试样，沿单个润湿或干燥路径的吸力变化几乎不会影响这种体积各向异性。然而，膨胀各向异性随着所经历的抽吸循环的增加而降低，并最终等于几次抽吸循环后的收缩。这对于具有较高初始干密度的试样更为明显，膨胀各向异性强于收缩各向异性。对于具有高吸力 (≥3.3 MPa) 的试样，沿单个润湿或干燥路径的吸力变化几乎不会影响这种体积各向异性。然而，膨胀各向异性随着所经历的抽吸循环的增加而降低，并最终等于几次抽吸循环后的收缩。这对于具有较高初始干密度的试样更为明显，膨胀各向异性强于收缩各向异性。对于具有高吸力 (≥3.3 MPa) 的试样，沿单个润湿或干燥路径的吸力变化几乎不会影响这种体积各向异性。然而，膨胀各向异性随着所经历的抽吸循环的增加而降低，并最终等于几次抽吸循环后的收缩。