不同应力状态下孔隙结构特征对土-水特征曲线的影响

针对传统土-水特征曲线测试仪无法实现荷载作用的不足,研制吸力控制式三轴试验装置,开展不同应力状态作用下土-水特征曲线试验,讨论应力状态对孔隙特征的作用,结果表明,固结压力和基质吸力均能使土体产生不可逆的收缩变形.固结压力越大,土颗粒就越紧密,孔隙比越小,孔隙尺寸和数量越小,渗透性越差,表现出较好的持水能力,空气难以进入土体,土体排水困难,导致进气值增大和减湿率减小.土-水特征曲线与孔隙结构特征的关系紧密,与应力状态无直接关系.固结压力对土-水特征曲线的影响是通过改变孔隙结构特征来体现的.孔隙结构特征相近时,应力状态对其土-水特征曲线不会产生影响.

Influence of pore structure characteristics on soil-water characteristic curves under different stress states

Since traditional instruments cannot apply stress in soil-water characteristic curve tests,we develop a suction controlled triaxial apparatus,by which soil-water characteristic curve tests are performed under different stress states.Further,the influence of stress state on the pore characteristics is discussed.The results show that both consolidation pressure and matrix suction can lead to the irreversible contraction deformation of soil.The soil under a larger consolidation pressure has a denser structure and a less void,leading to a smaller pore size and quantity.So it results in a worse permeability.Accordingly,it shows a better water retentivity.Air can hardly enter and water can hardly drain out,which give rise to a larger air entry value and a smaller slope of the soil-water characteristic curve.The soil-water characteristic curve of a compacted soil mainly depends upon current void ratio,not directly upon stress state.The influence of consolidation pressure on the soil-water characteristic curve is embodied in pore distribution properties.For similar pore distribution properties,the soil-water characteristic curve should be similar regardless of stress state.A larger consolidation pressure causes a less hysteresis.