Abstract
Takizawa volcanic ash soil and Gando clayey, soil were compacted in molds under a field water condition. The soil specimens were saturated and percolated with water using a low hydraulic gradient for a long time to increase the degree of saturation. Then, the specimens were placed in a hydraulic consolidometer.
The water pressuer at the bottom of specimen was kept 98 kN/m2 and the pressure on the top, of the specimen was changed from about 170 kN/m2 to 686 kN/m2 in four steps. The settlement of specimen, velocity of seepage water and distribution of pore' water pressure were observed after the rise of top pressure. When the consolidation of the fourth step was completed, the specimen was forced out from the mold and cut into pieces of 2 cm in height. Then, the volume and dry weight of those pieces were measured.
The principal results of experiment were as follows:
1) The final settlements of Takizawa and Gando specimens were 7.6% and 6.7% of, the initial thickness, respectively.
2) The final mean permeabilities of Takizawa and Gando specimens were decreased to one-third and one-half of the initial values, respectively.
3) The void ratio and permeability decreased gradually toward the bottom of the specimen.
A differential equation under steady-state condition after the completion of one-dimensional consolidation was introduced. The equation was described by a nominal strain and it was revised into a form that included the friction force between soil and mold. Based on a nonlinear, relation between stress and strain and between permeability and strain of the soil, specimens, the experimental, parameters expressing the relationships were determined by an ordinary consolidation and permeability test. To simulate the above-mentioned experimental results of hydraulic consolidation, the differential equation was integrated numerically, being, given the boundary condition of the experiments.
A comparison was made between calculated and observed values, as settlement, mean permeability and distribution of pore pressure, permeability and void ratio. The equation appeared to be in fairly good agreement in predicting above-mentioned observations.
