水泥土的孔隙分布及其对渗透性的影响

PORE DISTRIBUTION OF CEMENT-SOIL AND ITS EFFECT ON PERMEABILITY

以不同水泥掺量的水泥黏土为研究对象,进行核磁共振试验研究水泥掺量对微观孔隙分布的影响,进行变水头渗透试验研究水泥掺量对渗透性的影响,在此基础上调查水泥掺量对渗透性影响的微观机制。研究发现:水泥土的渗透系数随水泥掺量的增大而减小,其中在低水泥掺量(4%~12%)范围内急剧减小,在高水泥掺量(15%~25%)范围内呈现相对缓慢减小趋势;水泥土T2分布曲线均呈现三峰分布,三峰分别对应于小孔、中孔、大孔,随着水泥掺量增加,T2分布曲线总面积呈现减小趋势,其中在低水泥掺量范围内,第2峰、第3峰峰面积减小明显,在高水泥掺量范围内,第1峰峰面积显著减小。分析可知,在水泥掺量较低时,水泥水化作用优先堵塞大孔和中孔,导致渗透系数随水泥掺量增加而显著减小;在水泥掺量较高时,水泥掺量的增加主要减少小孔隙面积,大孔和中孔面积变化不大,此时增加水泥掺量对减小水泥土渗透系数的效果相对较差。

This paper takes the cement clay of different cement contents as the studied object.The samples of cement clay soil are used for nuclear magnetic resonance test to study the effect of cement content on the distribution of micro-pore.The samples are used for the variable water head penetration test to study the effect of cement content on permeability.On this basis,the paper investigates the microscopic mechanism of the effect of cement content on permeability.The study results show the follow.The permeability coefficient of cement-soil decreases as the cement content increases.It decreases intensely at cement content ranging from 4%to 12%,and decreases slowly at cement content ranging from 15%to 25%.There are three peaks in the T 2 distribution curves of cement-soil,which correspond to small pores,medium pores and large pores,respectively.As the cement content increases,the total area of T 2 distribution curve tends to decrease.At the stage of low cement content,the area of the second and third peaks diminishes obviously.But at the stage of high cement content,the area of the first peak diminishes obviously.Thus it can be seen that in the range of low cement content,the hydration of cement-soil is prior to block up large pores and medium pores,which makes the permeability coefficient decreases significantly with the increase of cement content.While in the range of high cement content,the area of small pores mainly declines with the increment of cement content.But that of large pores and medium pores has little difference,so the increase of cement content has little effect on the decrease of permeability coefficient of cement-soil.