摘要
针对潮水涨落或涌潮产生负压作用加剧古海塘粉土渗透变形和破坏的现象,研制了一种可以模拟负压作用影响的水平向渗透变形仪,以此为基础,开展不同负压(0、-3、-6、-9 kPa)、不同粉土干密度(1.40、1.45、1.50、1.55 g/cm3)条件下的渗透变形试验.结果表明:随着干密度增加,临界水力比降增大,抗渗能力增强,负压作用会相应降低临界水力比降并加快粉土的渗透破坏进程.通过分析提出了以现行规范确定的水力比降与流速双对数曲线为主、以渗透出水颗粒分布曲线为必要补充的粉土临界水力比降综合判别法.试验结果可为强涌潮海塘粉土防渗设计与评估提供参考.
Abstract
In response to the phenomenon of intensified permeability,deformation,and damage of ancient sea dike silty soil caused by tidal fluctuations or tidal surges generating negative pressure,a horizontal permeability deformation apparatus capable of simulating the influence of negative pressure was developed.Based on this apparatus,permeability deformation tests were conducted under different negative pressures(0,-3,-6,-9 kPa)and different dry densities of silty soil(1.40,1.45,1.50,1.55 g/cm3).The results indicate that with increasing dry density,the critical hydraulic gradient increases,enhancing the resistance to permeation.However,negative pressure reduces the critical hydraulic gradient correspondingly and accelerates the permeation damage process of the silty soil.Through analysis,a comprehensive judgment method for the critical hydraulic gradient of silty soil is proposed,which mainly relies on the double logarithmic curve of hydraulic gradient and flow velocity determined by current specifications,supplemented by the distribution curve of permeation effluent particles.The experimental results can provide a reference for the design and evaluation of impermeable silty soil in strong tidal surge sea dikes.
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