doi:10.3850/GI181

ABSTRACT

The effects of vacuum preloading when it is applied at the bottom surface of soil ground were experimentally studied in this paper. A laboratory testing program was undertaken on silty clay at water contents close to its liquid limit under vacuum pressure of 80kPa. The apparatus developed by the authors basically can afford the designated vacuum pressures. Moreover, it also allows for the measurement of settlement and volume of expelled water with time. Two types of test were conducted. The first type was done by applying vacuum pressure on the top surface of sample, named on-top method. In the second type, vacuum pressure was applied at the bottom surface of soil sample, named at-bottom method. Based on the results, it is shown that better results are given by
the at-bottom method compared to the on-top method. The final settlement induced by the at-bottom method is equal to about 1.3 times of that induced by the on-top
method. The results also showed that the shear strength of soil gained by the at-bottom method has increased up to a greater degree. It is recommended to apply the at-bottom method for particular projects i.e. land reclamation behind the sea dam.

Keywords: Vacuum preloading; on-top method; at-bottom method; soil improvement; shear strength.

© 2010 by Geotechnical Society of Singapore (GeoSS)