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Studies on the mechanism of soil consolidation from a view point of micro and macro soil sturctures

从微观和宏观土结构角度研究土体固结机理

基本信息

批准号：
06660291
负责人：
KOGA Kiyoshi
金额：
$ 1.28万
依托单位：
Iwate University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06660291/
关键词：
consolidation secondary consolidation mercury intrusion porosimetry permeability

项目摘要

Change in pore size distribution during consolidation processes was investigated using mercury intrusion porosimeter. Two cohesive soils were consolidated under the stress of 39-1,254 kPa in which load iincrement ratio was 1. Consolidation of specimen was interrupted at the end of the primary consolidation, in the midst of the secondary consolidation and 24 hours after the loading. Each specimen was frozen in liquid nitrogen and dried under a vacuum and subjected to MIP test. It was found in volcanic ash soil that the soil volume change during the primary consolidation is mainly due to the compression of the entrapped pores which includes inter-aggregate pores. On the other hand, soil volume change during the secondary consolidation was caused by the compression of free pores which exist in aggregates.Permeability change during secondary consolidation and stress relaxation processes was investigated using a newly developed consolidation-permeation meter in which the stress and strain of specimen can be automatically controlled by computer and applied water head difference can be precisely kept constant. Kaolin and Iwate volcanic ash soil were subjected to the test. It was revealed that reduction rate of permeability with respect t change in void ratio during the secondary consolidation was higher than the rate during the primary consolidation. The reason for such experimental results was considered as follows. There exists aggregate strucuture in these soils and permeating water mainly flows through inter-aggreagate pores. The inter-aggregate pores including wide portions of the pores are compressed in the primary consolidation process which results in relatively lower reduction rate, whereas the narrow portions of the pores are distorted and narrowed in the secondary consolidation process because of compression and deformation of the aggregates which leads to higher reduction rate. Change in permeability was not observed during the stress relaxation process.

采用压汞法研究了固结过程中孔隙尺寸分布的变化。两种粘性土在39- 1, 254 kPa的应力作用下，加荷比为1。在主固结末期、次固结中期和加载后24小时，试件的固结中断。将每个标本在液氮中冷冻并在真空下干燥，然后进行MIP测试。研究发现，火山灰土主固结过程中土体体积的变化主要是由于包埋孔隙（包括团聚体间孔隙）的压缩所致。另一方面，次固结过程中土体体积的变化是由于团聚体中自由孔隙的压缩引起的，本文采用一种新研制的固结-渗透仪研究了次固结和应力松弛过程中渗透率的变化，该仪器可由计算机自动控制试样的应力和应变，并可精确地保持外加水头差恒定。对高岭土和岩手火山灰土进行了试验。结果表明，次固结过程中渗透率随孔隙比变化的降低速率大于主固结过程中渗透率随孔隙比变化的降低速率。这样的实验结果的原因被认为如下。这些土壤中存在团聚体结构，渗透水主要通过团聚体间的孔隙流动。在主固结过程中，集料间的孔隙（包括较宽部分的孔隙）被压缩，导致相对较低的压缩率;而在次固结过程中，由于集料的压缩和变形，孔隙的狭窄部分被扭曲和变窄，导致较高的压缩率。在应力松弛过程中没有观察到渗透率的变化。