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

Chapter 1 PLANNING AND SCOPE
Table 1.1 Planning a Ground Investigation
Stage Action Responsibility of
I Obtain the services of an experienced geotechnical Developer or client
specialist
II Carry out desk study and air photograph or LIDAR (if Geotechnical specialist
available) interpretation to determine the probable
ground conditions at the site
III Conceptual design: optimize construction to minimize
geotechnical risk
Architect, structural engineer,
geotechnical specialist
IV Identify parameters required for detailed Geotechnical specialist
geotechnical calculations
V Plan ground investigation to determine ground Geotechnical specialist
conditions, and their variation, and to obtain
geotechnical parameters.
VI Define methods of investigation and testing to be Geotechnical specialist
used
VII Determine minimum acceptable standards for Geotechnical specialist
ground investigation work
VIII Identify suitable methods of procurement Geotechnical specialist, lead
professional
design, developer or client
1.6.1 Spacing of Pits and Borings
The required spacing depends very much on the size and type of the project and on the terrain and
subsurface conditions. For a start, borings should initially be widely spaced and subsequently,
intermediate borings can be carried out as required, so that sections can be drawn with reasonable
accuracy. In uniform conditions, spacing may be 25m to 150m or more but spacings of 10m or less
may be required to examine detailed problems and or or in erratic conditions. Examples of typical
spacing requirements are given in Table 1.2 and illustrated in Fig 1.1. Where structures are to be
founded on slopes, the overall stability of the structure and the slope must obviously be investigated,
and to this end a deep borehole near the top of the slope will be very useful.
It must be emphasised however, that the requirements of individual sites may vary considerably
from those given.
1-6 March 2009