赵梦怡, 谢强, 郭永春, 杨毅凡. 2018: 非饱和成都黏土瞬时剖面法渗透性试验研究. 工程地质学报, 26(3): 620-625. DOI: 10.13544/j.cnki.jeg.2017-177
    引用本文: 赵梦怡, 谢强, 郭永春, 杨毅凡. 2018: 非饱和成都黏土瞬时剖面法渗透性试验研究. 工程地质学报, 26(3): 620-625. DOI: 10.13544/j.cnki.jeg.2017-177
    ZHAO Mengyi, XIE Qiang, GUO Yongchun, YANG Yifan. 2018: EXPERIMENTAL STUDY OF UNSATURATED PERMEABILITY OF CHENGDU CLAY BY INSTANTANEOUS PROFILE METHOD. JOURNAL OF ENGINEERING GEOLOGY, 26(3): 620-625. DOI: 10.13544/j.cnki.jeg.2017-177
    Citation: ZHAO Mengyi, XIE Qiang, GUO Yongchun, YANG Yifan. 2018: EXPERIMENTAL STUDY OF UNSATURATED PERMEABILITY OF CHENGDU CLAY BY INSTANTANEOUS PROFILE METHOD. JOURNAL OF ENGINEERING GEOLOGY, 26(3): 620-625. DOI: 10.13544/j.cnki.jeg.2017-177

    非饱和成都黏土瞬时剖面法渗透性试验研究

    EXPERIMENTAL STUDY OF UNSATURATED PERMEABILITY OF CHENGDU CLAY BY INSTANTANEOUS PROFILE METHOD

    • 摘要: 非饱和渗透系数是土体渗流分析的基础,成都黏土作为一种典型的非饱和膨胀土,具有吸水膨胀、失水收缩的特性,在受侧限的浸水过程中,土颗粒的膨胀致使孔隙体积减小,渗透性降低,使得直接对其进行非饱和渗透试验十分困难。根据瞬时剖面法的原理,利用EC-5土壤水分传感器测含水率、MPS-2电介质水势传感器直接同步测量同一位置的基质吸力,通过水平渗透试验研究了非饱和成都黏土在侧限条件下的渗透性。含水率和基质吸力的同步测量,保证了其测试条件的一致性,避免了采用其他土水特征曲线的影响。试验表明,试样的非饱和渗透系数为(1.33×10-11~3.14×10-9)m·s-1,非饱和渗透系数与基质吸力并非单调线性关系。基质吸力较高时,受膨胀土颗粒吸水膨胀的影响,渗透系数未出现明显变化,基质吸力降低到一定程度后,渗透系数快速增大。试验结束时土体已接近饱和,土中气体排出较慢,过水断面增加缓慢,促使渗透系数仍然持续增大。采用VG模型拟合k-s曲线,拟合参数α=0.048 kPa-1n=1.79,m=0.48,试验结果可以用于成都黏土地区的渗流分析。

       

      Abstract: Unsaturated hydraulic conductivity is the foundation of seepage analysis in soil. The theory system of unsaturated seepage is not mature enough, so the best method to obtain unsaturated hydraulic conductivity is measurement directly. There is not a few measurement technology of unsaturated hydraulic conductivity with long cycles and higher requirements on the environment. Chengdu clay is a kind of typical unsaturated expansive soil and has the characteristics of swelling and shrinkage. In the process of infiltration under confined condition, the expansion of the clay particles causes pore volume decrease, and lower permeability. Unsaturated infiltration experiments of Chengdu clay are quite difficult to be carried out. According to the instantaneous profile method, infiltration experiments were conducted to study the unsaturated permeability of Chengdu clay under confined condition. To do so, water contents and matric suctions were respectively monitored by EC-5 soil moisture sensors and MPS-2 dielectric water potential sensors. Synchronous measurements of moisture content and matrix suction, ensured the consistency of test conditions and avoided the influence of using other soil water characteristic curve. Considering the ceramic plate probe of MPS-2 is fragile and convenient components installed, a removable cuboid permeameter(50 cm long, 10 cm wide and 10 cm high) was custom-made. The dry density of the soil sample is 1.7 g·cm-3 and initial water content is 27%.The result shows that, during water infiltration, the unsaturated hydraulic conductivity of the sample is between 1.33×10-11 and 3.14×10-9 m·s-1, and it does not change linearly with matric suction. At the beginning of infiltration, i.e.when the matric suction is high, the hydraulic conductivity does not change significantly with the influence of expansion of clay particles. When the matric suction reduces to a certain value, the hydraulic conductivity increases rapidly. At the end of the experiment, the sample was near saturation, and presented an increasing trend of hydraulic conductivity because the discharge of gas in the sample is very slow and effective flow cross sectional area increases slowly. Derived from fitting the VG model to the experimental data, the α value was 0.048 kPa-1, the n value was 1.79 and the m value was 0.48. The conclusion can be utilized for seepage analysis of Chengdu clay area.

       

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