Water retention and volumetric characteristics of intact and re-compacted loess
Water retention and volumetric characteristics of intact and re-compacted loess
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DOI：
10.1139/cgj-2015-0364
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发表时间：
2016-08-01
影响因子：
3.6
通讯作者：
Baghbanrezvan, Sina
中科院分区：
文献类型：
--
作者：
Ng, Charles Wang Wai;Sadeghi, Hamed;Baghbanrezvan, Sina
通过室内试验，研究了微结构对黄土持水曲线和干湿变化的影响。采用轴平移技术和蒸汽平衡技术分别将抽吸控制在0-400 kPa和4-140 MPa。在整个吸力研究范围内，观察到黄土WRC的滞后现象。与再压实黄土相比，原状黄土在20 kPa以下的吸力范围内表现出更明显的滞后性，这可以用墨水瓶孔颈效应或收缩孔隙来解释。压汞法和扫描电子显微镜测试的微观结构证据支持这一假设。当吸力大于30 kPa时，再压实黄土的滞回特性大于原状黄土。介绍了一种概念模型，它将WRC与相应的孔径密度（PSD）函数联系起来。关于体积变化，更明显的干燥引起的收缩，但在较低的吸力屈服，观察到再压实黄土。这与压缩测试结果一致。应力对PSD和收缩的大孔的变化具有显著影响，导致主润湿曲线的移动和不太明显的滞后。原状黄土表现出与应力相关的湿陷和干缩特性。
A laboratory testing program was conducted to investigate the effects of microstructure on the water retention curve (WRC) and wetting-drying induced volume change in loess. The axis translation and vapor equilibrium techniques were adopted to control suction in the range of 0-400 kPa and 4-140 MPa, respectively. Hysteresis in the WRC of loess was observed for the entire range of suction studied. Compared to re-compacted loess, intact loess exhibits a more pronounced hysteresis in the suction range below 20 kPa, which can be explained by the ink-bottle pore neck effect or constricted pores. The hypothesis is supported by microstructural evidence of mercury intrusion porosimetry and scanning electron microscopy tests. However, re-compacted loess exhibits larger hysteresis than intact loess for suctions above 30 kPa. A conceptual model was introduced, which links WRC to the corresponding pore-size density (PSD) function. Regarding volume change, more noticeable drying-induced shrinkage, but yielding at a lower suction, was observed for re-compacted loess. This is consistent with the compression test results. Stress has a significant effect on change of PSD and constricted macropores leading to a shift in the main wetting curve and a less pronounced hysteresis. Intact loess exhibits a stress-dependent wetting-induced collapse and drying-induced shrinkage.