Geoscience Reference
In-Depth Information
Table 1.4 Suggested test spacing.
Phase of project
Typical map scale
Boreholes per hectare
Approximate spacing
IAS
1: 10,000
0.1 to 0.2
200 m to 400 m
Planning
1: 5,000
0.5-1.0
100 m to 200 m
Preliminary design
1: 4,000 to 1: 2,500
1 to 5
50 m to 100 m
Detailed design
1: 2,000 (Roads)
5 to 10
30 m to 100 m
1: 1,000 (Buildings or
10 to 20
20 m to 30 m
Bridges)
A geo-environmental investigation has different requirements. The following
Tables would need to be adjusted for such requirements.
=
10,000m 2 .
1 Hectare
1.5 Planning of groundwater investigation
Observation wells are used in large scale groundwater studies.
The number of wells required depends on the geology, its uniformity, topography
and hydrological conditions and the level of detail required.
The depth of observation well depends on the lowest expected groundwater level
for the hydrological year.
Table 1.5 Relation between size of area and number of
observation points (Ridder, 1994).
Size of area under
No. of groundwater
study (hectare)
observation points
100
20
1,000
40
10,000
100
100,000
200
1.6 Level of investigation
The following steps are required in planning the investigation:
- Define the geotechnical category of the investigation. This determines:
The level of investigation required;
Define the extent of investigation required; and
Hire/use appropriate drilling/testing equipment.
1.7 Planning prior to ground truthing
Prepare preliminary site investigation and test location plans prior to any ground
truthing. This may need to be adjusted on site.
 
 
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