Site investigation - Geotechnical Investigation and Design Tables - page 13

Table 1.14 Quality of a detailed investigation.

Influencing factors Quality of site investigation Comments

Good Fair/Normal Poor

Quantity of factors 70% 40% to 70% 40% 10 factors provided herein

Phasing of investigation Yes No Refer Table 1.2

Safety and environmental plan Yes No Refer Table 1.7

Test/Hectare
• Buildings/Bridges

Refer Table 1.4 for detailed design.
Tests can be boreholes, test pits,
cone penetration tests, etc. Relevant
tests from previous phasing included.

20 10

5

10
5

• Roads 10

Extent of investigation
reflects type of development

Yes No Refer Table 1.8

Depth of investigation
adequate to ground

Yes No Refer Table 1.8

Sample amount sufficient for
lab testing

Yes No Refer Table 1.11

Specimen size accounting for
soil structure

Yes No Refer Table 1.13

% of samples testing in the
laboratory

Assuming quality samples obtained in
every TP and every 1.5 m in BHs.

20% 10% 10%

Sample tested at relevant
stress range

This involves knowing the depth of
sample (for current overburden
pressure), and expected loading.

Yes No

Budget as % of capital works 0.2% 0.2% Value should be significantly higher

for dams, and critical projects
(Table 1.16).

1.15 Costing of investigation
•

The cost of an investigation depends on the site access, local rates, experience
of driller and equipment available. These are indicative only for typical projects.
For example, in an ideal site and after mobilisation, a specialist Cone Penetration
Testing rig can produce over 200m/day.

•

There would be additional cost requirements for safety inductions, traffic control,
creating site access, distance between test locations.

•

The drilling rate reduces in gravels.