Vacuum consolidation of Sri Lankan peaty soil

Abstract

Vacuum consolidation was used for the first time in Sri Lanka to improve highly compressible low strength peaty soil encountered in the Southern Expressway Project. Prior to the actual treatment programme, few trial embarkments were built to study the feasibility and the effectiveness of the vacuum consolidation method in improving the Sri Lankan peaty soil. At the trial embankment sites the founding soil mainly consisted 01 very soft highly compressible peaty or organic soil layers of thickness varying from 3 - 8 m. The soft layers were improved by a combined vacuum consolidation and surcharging with 5 to 9m high stage constructed embankments to compensate the primary consolidation settlements and tominimize the secondary settlements that can take place in the actual road embankments. A brief description of the construction of the vacuum consolidation system and embankment, the details of the field instrumentation and their observed behavior during the monitoring period are presented in this study, The improvement in the peaty soil due to the soft ground treatment was assessed from the data obtained through the field monitoring program and the results obtained from the laboratory and field tests carried out on improved and unimproved ground areas. The obtained data was analyzed to investigate the effectiveness of vacuum consolidation process in improving the properties of Sri Lankan peaty soils. Furthermore, the obtained data was analyzed to quantify the improvement in the strength, and comprehensibility properties of Sri Lankan peaty soils as a results of the over consolidation due to vacuum consolidation method'