Site investigation - Geotechnical Investigation and Design Tables - page 6

or a drilling rig with a certain mast height and permission from the electrical safety
authority before proceeding.

•

The planning should allow for any physical obstructions such as coring of a
concrete slab, and its subsequent repair after coring.

Table 1.7 Planning checklists.

Type Items

Informative Timing. Authority to proceed. Inform all relevant stakeholders. Environmental

approvals. Access. Site history. Physical obstructions. Positional accuracy
required.

Site specific Traffic controls. Services checks. Possible shut down of nearby operational plant.

safety plans Isolations required.

S.I Management Checklists. Coordination. Aims of investigation understood by all. Budget limits

where client needs to be advised if additional SI required.

1.8 Extent of investigation
•

The extent of the investigation should be based on the relationship between the
competent strata and the type of loading/sensitivity of structure. Usually this infor-
mation is limited at the start of the project. Hence the argument for a 2 phased
investigation approach for all but small (GC1) projects. For example in a piled
foundation design:
-

The preliminary investigation or existing nearby data (if available) determines
the likely founding level; and

- The detailed investigation provides quantitative assessment, targeting testing

at that founding level.

•

The load considerations should determine the depth of the investigation:
- > 1 . 5 × width (B) of loaded area for square footings (pressure bulb ∼ 0.2 q

where q = applied load).

- > 3 . 0 × width (B) of loaded area for strip footings (pressure bulb ∼ 0.2 q).

•

The ground considerations intersected should also determine the depth of the
investigation as the ground truthing must provide:
-

Information of the competent strata, and probe below any compressible
layer.

- Spacing dependent on uniformity of sub-surface conditions and type of

structure.

•

Use of the structure also determines whether a GC 2 or GC 3 investigation applies.
For example, a building for a nuclear facility (GC3) requires a closer spacing than
for an industrial (GC2) building.