Construction unit of soft soil improvement
Soils having poor engineering characteristics now demand more
consideration in construction activity, especially in regions where
good quality ground is in short supply. Surcharge preloading with
prefabricated vertical drains (PVDs) is one of the most popular
techniques for ground improvement involving soft soils. The
inclusion of the PVDs into the ground artificially reduces the
drainage path length, thereby speeding up the consolidation process
which may otherwise take many years to achieve substantial
completion for soft soil deposits. However, the surcharge loading
required to ensure such deposits undergo acceptably low amounts of
settlement post-construction are often so large that, in
maintaining an adequate factor of safety against slope instability,
it may prove rather time consuming to apply the necessary fill
layers. In this regard, use of the vacuum consolidation technique
in conjunction with surcharge preloading and PVDs can enhance the
efficiency of ground improvement works. The vacuum preloading
technique, originally proposed by Kjellman (***2), has over the
past three decades evolved to become a viable, more cost-effective
solution for ground improvement projects worldwide. This has been
largely due to improvements in geosynthetic/PVD and vacuum pump
technology.
