Abstract
The liquefaction countermeasure technical method, whereby the liquefaction strength is enhanced by making sand deposit in the state of unsaturation, is currently under study. The author et al have suggested a simple method of verifying the persistence of residual air using the undisturbed sample under ordinary temperature and sampling underground water; and have actually implemented the method in the adjacent ground with the foundation of viaduct pneumatic caisson where the leaked air during the construction was considered to have been trapped. We demonstrated the method of correcting the influence of the pressure of sampling specimen as well as of the dissolved air, and studied the precision of required degree of saturation. As the result, it has been shown that the residual air entrapped in the sand deposit is sustainable for as long time as about 28 years.
