Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 8 GROUND IMPROVEMENT
c) Soils subjected to improvement works are usually very soft in nature. Standard Penetration Test
(SPT) is not suitable for soft soil layer. It is advisable to retrieve undisturbed soil samples from
the ground for laboratory tests which include Undrained Unconsolidated (UU) Triaxial test and
One Dimensional Consolidation Test using Odeometer. In addition, in-situ tests such as Vane
Shear test and Piezocone are recommended in soft soils sensitive to disturbance such as marine
clay is highly recommended.
d) Transition zone shall be provided in the ground improvement design if the project used more
than one type of ground improvement methods. This is most crucial if the ground improvement
methods pose a different allowable long term settlement, e.g., bridge and bridge approach,
culverts etc.
e) Due to the complexities and uncertainties of the ground conditions as well as the simplification of
design formulae in the analysis and design, it is strongly recommended that the instrumentation
monitoring scheme shall be provided during the construction works for design verification
purposes. Some provisions in the Bill of Quantities shall also be provided to cater for any design
changes during construction.
March 2009 8-11