| Parameter | GEOSS (Singapore) | BS 8004 (UK) | Eurocode 7 | |-----------|-------------------|--------------|-------------| | Max jacking force | 80% of pile structural capacity | 75% (driven piles) | 85% (static load) | | Heave limit | 15 mm at 1 m distance | 25 mm at 2 m | Not explicitly defined | | Verticality tolerance | 1:200 | 1:75 | 1:100 | | Restrike period (clay) | 3 to 7 days after initial jacking | 1 to 5 days | 2 to 10 days | | Pre-boring permission | Required if SPT > 50 or clay N > 20 | Optional | By specification |
The GEOSS standard is notably stricter on ground movement and verticality, recognizing Singapore's density of underground infrastructure.
Based on GEOSS technical references, BCA’s “Code of Practice for Foundations” (CP 4), and local project case histories shared on GEOSS, the following good practices apply: | Parameter | GEOSS (Singapore) | BS 8004
Published by the Geotechnical Society of Singapore (GEOSS) | Technical Reference Guide
Driving into OA with SPT-N > 60 can stall the jack before reaching design toe level.
GEOSS Solution: Either (a) redesign with a smaller pile section, (b) implement vibro-replacement prior to jacking, or (c) switch to a hybrid jack-drill method (allowed only under special supervision). Based on GEOSS technical references, BCA’s “Code of
In contrast to hammer-driven or vibratory hammers, jacked piles are installed by applying a static vertical force using hydraulic jacks reacting against the weight of a heavy rig or previously installed piles. This method is particularly suited for Singapore’s geological profile:
The advantages are clear: zero impact noise (critical near hospitals and residential estates like Toa Payoh or Queenstown), no harmful vibrations (protecting MRT tunnels and heritage buildings), and precise control of final set. In contrast to hammer-driven or vibratory hammers, jacked
Yet, these advantages can only be realized through disciplined good practice—hence the creation of the GEOSS guide.
One of the most valuable sections of the GEOSS good practice is the mandatory documentation protocol. For every jacked pile, the following must be recorded and submitted to the Qualified Person (QP):
These records become the link between as-built conditions and future maintenance or additional loading. Without this disciplined paperwork, the foundation cannot be certified by BCA (Building and Construction Authority, Singapore).