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为了揭示非饱和土在自然环境和轴平移环境两种条件下,基质吸力测试数据存在差异的原因,分别研究了表面张力系数和难充水微孔隙在相同吸力作用下对含水率的影响。一方面,表面张力系数随压力的增大而小幅减小,同一基质吸力条件下采用轴平移技术时对应的含水率较自然状态有偏小的趋势;另一方面,由于一端封闭微孔隙的存在,较高的孔隙气压力必然促使土中水进入部分难充水微孔隙,从而同一基质吸力条件下轴平移技术对应的含水率较自然状态又有升高的趋势。因此,在特定基质吸力条件下,轴平移方法得到的含水率较自然状态偏大还是偏小取决于上述两方面的综合效应。毛细上升试验和针对一端封闭微孔隙模型的研究表明,一端封闭微孔隙的存在对土-水特征曲线的影响远远大于表面张力系数变化的影响。针对石英砂、砂土和黏土的两种SWCC测试结果表明,随土颗粒逐渐变细,轴平移技术对SWCC的影响越来越大。从而进一步印证,张力计法和轴平移方法在测试黏土土-水特征曲线方面存在差异的原因在于一端封闭微孔隙的存在。
In order to reveal the difference of matric suction test data under both natural environment and axial translational environment, the effects of surface tension coefficient and water-filled micro-pore under the same suction on moisture content were studied. On the one hand, the surface tension coefficient decreases slightly with the increase of pressure, and the corresponding moisture content tends to be smaller than the natural state under the same substrate suction condition. On the other hand, due to the presence of closed micropores at one end , The higher pore pressure will inevitably cause the soil water to enter some of the difficult water-filled micro-pores, so that the corresponding moisture content of the axial translation technology under the same substrate suction has a tendency of higher than the natural state. Therefore, under certain substrate suction conditions, the axial moisture content obtained by the axial shift method is larger or smaller than the natural state depends on the above two aspects of the combined effect. The capillary ascending test and the study of one-end closed micropore model show that the existence of one-end closed micropore has a far greater effect on the soil-water characteristic curve than the change of the surface tension coefficient. Two kinds of SWCC tests for quartz sand, sand and clay show that as the soil particles become thinner, the influence of the axial translation technology on the SWCC becomes larger and larger. It is further confirmed that the reason why there is a difference between Tensiometer and axial translation methods in testing clay soil-water characteristic curve lies in the existence of one-end closed micropore.