固结蠕变下软土微观结构参数的定量分析

Microstructure Change of Soft Soil under Consolidation Creep

为了探究土的微观结构特性和更加准确的描述土的变形过程,从微观上分析珠三角地区软土的固结蠕变,对软土的微观结构特征、孔隙个数和直径、孔隙和颗粒丰度、孔隙定向频率等方面进行了定量分析,对代表性广州番禺地区的土样试验结果表明:原状土样的微观结构主要是以蜂窝状和基质状结构为主,土体颗粒接触方式主要为点-点接触和点-面接触;当施加轴向固结荷载时土体的结构发生变化,轴向荷载较大时,土体的微观结构以紧密的骨架状和紊流状结构为主,土体颗粒的接触方式以面-面接触为主。软土在蠕变过程中,土体颗粒和孔隙大小的变化都遵循大孔隙优先改变原则,颗粒和孔隙的边界变得圆滑且形状趋向于扁圆形。蠕变后,颗粒和孔隙的个数有明显增加,直径都有明显减少,孔隙丰度值和复杂度有所降低。原土的分形维数高于土体蠕变变形后的分形维数。当固结应力增大时,土中孔隙的分形维数不断减小,大孔隙不断减少,大颗粒破损,小颗粒被挤入大孔隙中,颗粒和孔隙朝着均匀化方向发展。

To understand the consolidation creep of the Zhujiang(Pearl)River deltaic region,the microstructure and deformation of soft soil were studied using reprehensive soils from Panyu area of Guangzhou,South China,the number and pore diameter,pore and grain abundance,pore directional frequency,etc,were quantitatively analyzed.Results show that the undisturbed soil featured honeycomb and matrix microstructure,and the particle contact was point-point or point-surface.Under a large axial consolidation load,the microstructure of soil was dominated by tight skeleton and turbulent structure,and the particle contact changed to surface-surface.The creeping began in larger particles and pores,and the outlines of particles and pores smoothed out and tend to be squashed.After creeping,the number of particles and pores increased,the diameter decreased,the pore abundance and complexity decreased,and the fractal dimension of the soil deceased.Under the constant loading,bigger pores continued to decreased,bigger particles tended to be crashed,while smaller particles were squeezed into bigger pores,and all particles and pores went homogenized.