Effects of the fines contents on pore water pressure measurements in dynamic triaxial tests
Date Issued
2006
Date
2006
Author(s)
Wu, Shau-Hua
DOI
zh-TW
Abstract
Abstract
In the ordinary cyclic triaxial tests, the researchers often use small and stiff Teflon tubes to connect the cap and bottom of the specimen to the water pressure transducer. They assume that there is no change in the volume of specimen and measurement system in undrained tests. In fact, the volume change exists in the dynamic testing. When the pore water pressure changes in a certain location of the specimen, not only the water pressure transmission within the specimen, but the pressure would probably lead to the volume change of the water pressure measuring system. There must be water flow to fill the volume change, that the ends pore water pressure transducer can experience the pore water pressure changes. Water flow can occur quickly and the measurements reflect the pore water pressure change immediately for low fines contents specimen with higher permeability. Howerer, for the high fines contents specimen with lower permeability, the measurements cannot reflect the pore water pressure changes inside the specimen immediately.
This study evaluates the effects of the fines contents on pore water pressure measurements. The pore water pressures at different locations (both ends, mid-height, 3/4-height) in the test specimen were measured in the dynamic triaxial tests. It is found that in an ordinary triaxial test, for specimen of lower fines contents, the pore water pressure sensors can obtain the same pore water pressure value. For specimen with higher fines contents, different pore water pressure values were obtained at different locations. The pore water pressure at 3/4-heigh of the specimen reach the initial effective pressure first, followed by that at mid-height of the specimen, and then that at the ends. Therefore, there is probable overestimate of the liquefaction resistance of the specimen with high fines contents in the ordinary dynamic triaxial test with pore water pressure measurements at the ends. This study obtain the correction ratios to adjust the liquefaction resistances obtained in the ordinary dynamic triaxial tests according to the permeability of the specimens.
Subjects
細料含量
液化
動力三軸試驗
體積變化
孔隙水壓
量測系統
fines contents
liquefaction
dynamic triaxial test
volume change
pore water pressure
compliance
measurements
Type
thesis
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