2019 Volume 75 Issue 3 Pages 303-315
In the vacuum consolidation method, the pressure under the air-tight sheet increases according to ground surface settlement. An air-water separation system for the vacuum consolidation method (VCM) was developed to improve this issue and enhance the vacuum effect. Although it has been demonstrated up to today that the system can obtain a higher vacuum pressure, the suppression effect of the new type VCM against deformation has never been discussed. In this study, therefore, mainly to reveal the suppression effect of the new method against deformation, several numerical simulations were conducted by using a soil-water coupled analysis code, GEOASIA, which mounts the macro-element method with discharge and drainage functions of vertical drains. The main findings of this study are as follows: 1) The air-water separation system has a high efficiency against deformation. Especially, the method remarkably restricts settlement that occurs after stopping vacuum pumps because it has a high preloading effect. 2) The conventional VCM also restricts deformations including a lateral deformation even if large settlement occurs. This is because the vacuum loading effect is maintained even though the pressure under the airtight sheet increases according to ground surface settlement. 3) Short-term constructions that have never been attempted can be performed in both the type VCMs. The above discussions demonstrated that the numerical simulation method used in this study allows the selection of effective countermeasures and economical construction conditions.
