4 Ground improvement by deep vibratory methods
effect. In these cases, soil characteristics can only be improved by adding
granular material during the process of forming compacted stone columns
(vibro replacement stone columns).
Following a historic overview of the development of these soil improvement methods, two chapters deal with the improvement of granular soils
by the vibro compaction method (Chapter 3) and of fine-grained cohesive
soils by the vibro replacement stone column method (Chapter 4). The chapters include detailed descriptions of the equipment used and the specific
physical processes controlling the two methods and provide state-of-theart design principles, including methods to assess and mitigate seismic risk
when applying either improvement method. Quality control procedures,
the evaluation of suitable soils, and practical method limitations together
with recent case histories complete these chapters. Chapter 5 deals with
method variations, related processes and, especially, with vibro concrete
columns where the stone backfill, as with stone columns, is replaced by
concrete.
In Chapters 6 and 7, environmental considerations and contractual implications of these ground improvement methods will be described.