非饱和Q3黄土渗气特性试验研究

 为研究非饱和原状和重塑Q3黄土渗气系数的变化规律及其两者的差异，以改进的三轴渗气仪为手段，进行一系列考虑干密度、含水率和各向异性等因素影响的渗气试验。研究结果表明：根据Fick定律和Darcy定律推导的渗气系数计算公式，在较低压力下两者计算结果差别不大，而在较高压力下，Darcy定律计算结果要优于Fick定律；非饱和原状黄土中气体流动遵循Darcy定律，原状黄土渗气系数随着干密度和含水率的增大而减小，且最优含水率以后变化较为明显；由于原状Q3黄土各向异性，竖向原状试样渗气系数始终大于同一埋深横向试样的渗气系数；相同干密度条件下，含水率对重塑黄土渗气系数的影响要比原状黄土大。根据试验结果提出考虑干密度、充气孔隙度(饱和度)和各向异性等因素影响的原状黄土渗气系数计算公式，其计算结果与试验结果吻合较好。

EXPERIMENTAL RESEARCH ON GAS PERMEABILITY OF UNSATURATED Q3 LOESS

A series of tests considering influences of soil water content,dry density,and anisotropic property,were carried out to research the gas permeability coefficient of unsaturated undisturbed and remoulded Q3 loess,by using a modified triaxial gas permeable apparatus.The results show that,in a lower pressure condition,the results of gas permeability coefficient calculated by Darcy law and Fick law get close to each other;and in a higher pressure condition,the method obtained from Darcy law has an advantage over that got by Fick law.Gas flow of unsaturated undisturbed loess can be expressed by Darcy law.Gas permeability coefficient of unsaturated undisturbed loess decreases with the increase of water content and dry density;and this variation is more obvious in excess of optimum water content.Gas permeability coefficient of vertical undisturbed loess samples is greater than that of horizontal samples in the same buried depth because of anisotropic property.Comparing with gas permeability coefficient of undisturbed loess samples in case of same dry density,the influence of water content on that of remoulded loess is more significant.According to test data,formulas are proposed to compute gas permeability coefficient considering the influence of dry density,gas-filled porosity(saturation ratio) and anisotropic property.The computed results are in accordance with test data.