Abstract:
Very frequently, the infrastructure development activities, especially highways, railways, water supply schemes, etc, and related structures are now constructed on land with poor ground support conditions, basically due to the unavailability of good ground for infrastructure construction. Further, countries like Japan, Singapore, Malaysia etc., where the developable areas are scarce, reclaim land from the sea where the underground conditions are very much more unfavorable for construction. Sri Lanka is now facing a similar situation and is on par with the world where most of the structures and other related constructions are being constructed on improved grounds, previously considered as "not good" for any construction.
Where poor ground conditions make traditional forms of construction expensive, it may be economically viable to attempt to improve the engineering properties of the ground before building on it. This can be done by reducing the pore water pressure and the volume of voids in the soil, or by adding stronger materials. In earlier times, poor ground areas have usually been avoided or structures with deep foundations such as a bridge supported roadway have been constructed over
the top of the loose deposits. Many types of site improvement techniques are now available that allow constructions such as embankment and interchanges to be constructed directly on improved ground. Soil which is highly compressible is prone to volume change when a load is applied. This leads to settlement. Fine-grained soils which have been compressed and then allowed to swell, experience a smaller volume change when re-compressed. Loosely-compacted coarse-grained soils may exhibit little change in volume under static loads, but become unstable and exhibit large volume changes
when either vibrated or flooded and then drained.
