Study on Expansion Characteristics of Expansive Soil Under Dry-wet Cycle Conditions
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摘要: 通过对北疆膨胀土开展干湿循环条件下无荷膨胀率、有荷膨胀率及微观扫描试验，探讨膨胀土吸水膨胀的特性及微观机理。试验结果表明：（1）在无荷膨胀率试验中，随着时间的增加，无荷膨胀率逐渐增加，在试验后期逐渐趋于稳定；随着干湿循环次数的增加，无荷膨胀率逐渐减小，第5次循环后趋于稳定值；（2）在有荷膨胀率试验中，随着时间的增加，有荷膨胀率逐渐增加且试验后期趋于稳定，上覆荷载越大，膨胀土试样有荷膨胀率越小；随着干湿循环次数的增加，有荷膨胀率逐渐减小，有荷膨胀率随循环次数及上覆荷载的增大而减小；（3）电镜扫描结果显示，无循环膨胀土试样结构较为牢固，经过干湿循环作用，膨胀土试样微观结构发生明显变化，土体微观结构逐渐破碎，颗粒面积减少，出现较多微小孔隙，导致膨胀率随循环次数的增加而逐渐减小。研究成果可为北疆膨胀土稳定性评价提供理论基础。Abstract: The characteristics and micro-mechanism of water absorption and expansion of expansive soil were discussed by carrying out no-load expansion rate, loaded expansion rate, and micro-scanning test on expansive soil in northern Xinjiang under dry-wet cycle conditions. The test results show that: (1) In the no-load expansion rate test, with the increase of time, the no-load expansion rate gradually increased and gradually stabilized in the later stage of the test. With the increase in the number of dry-wet cycles, the unloaded expansion rate gradually decreases and tends to be stable after the fifth cycle. (2) In the load expansion rate test, with the increase of time, the load expansion rate gradually increases and tends to be stable in the later stage of the test. The larger the overlying load, the smaller the load expansion rate of the expansive soil sample; with the increase in the number of dry-wet cycles, the loaded expansion rate decreases gradually, and the loaded expansion rate decreases with the increase of the number of cycles and the overlying load. (3) The results of scanning electron microscope show that the structure of expansive soil sample without cycle is relatively firm. After the dry-wet cycle, the microstructure of the expansive soil sample changes obviously, the microstructure of soil mass breaks gradually, the particle area decreases, and more tiny pores appear, which leads to the decrease of expansion rate with the increase of cycle times. The research results can provide a theoretical basis for the stability of expansive soil in northern Xinjiang.
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Key words:
- dry-wet cycle /
- expansive soil /
- expansion rate /
- micro-mechanism
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表 1 膨胀土基本物理性质指标
土样名称 天然含水率
w/%天然干密度
ρd/(g·cm−3 )塑性指数
IP液性指数
IL最大干密度
ρdmax/ (g·cm−3 )最优含水率
wopt/%风干含水率
wair/%液限
wL/%塑限
wP/%黄色泥岩 14.8 1.60 41.2 −0.13 1.67 18.9 8.0 61.3 20.1 
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表 3 颗粒参数
循环
次数颗粒
总数颗粒总
面积/μm2颗粒平均
尺寸/μm颗粒面积
占比/%颗粒平均
周长/μm0 449 33.601 0.075 33.294 1.114 1 520 29.104 0.064 28.517 1.009 3 557 27.559 0.059 26.214 0.807 5 596 26.671 0.057 27.299 0.783 7 613 26.367 0.053 26.109 0.801 9 610 26.339 0.046 26.081 0.814
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