Soil Investigation

The element of a site investigation depend heavily on the project but generally should provide the following :

1. Information to determine the type of foundation required (shallow or deep)
2. Information to allow the geotechnical consultant to make a recommendation on the allowable load capacity of the foundation.
3. Sufficient data/laboratory tests to make settlement predictions.
4. Location of the groundwater table. For certain projects, groundwater table fluctuations may be required. These can require installation of piezometers and monitoring of the water level in them over a period of time.
5. Information so that the identification and solution of construction problems (sheeting and dewatering or rock excavation) can be made.
6. Identification of potential problems (settlements, existing damage, etc) concerning adjacent property.
7. Identification of environmental problems and their solution.

METHOD OF EXPLORATION.

A. DISTURB SAMPLES TAKEN

1. Auger Boring
Depth : Depends on equipment and time available, practical depths being up to about 35 m.
Applicability : All soils.

2. Rotary drilling, wash boring, percussion drilling.
Depth : Depends on equipment, most equipment can drill to depths of 70 m or more.
Applicability : All soils.

3. Test pits and open cuts.
Depth : As required, usually less than 6 m, use power equipment.

B. UNDISTURB SAMPLES TAKEN.

1. Auger drilling, rotary drilling, percussion drilling, wash boring.
Depth : depends on equipment, as for disturbed sample recovery
Applicability : thin-walled tube samples and various piston samplers are used to recover
samples from holes advanced by these methods. Commonly, samples of 50-
to-100 mm diameter can be recovered.

2. Test pits.
Depth : Same as for disturbed samples
Applicabilty : hand-trimmed samples. Careful trimming of sample should yield the least
sample disturbance of any method.


(taken from Joseph E. Bowles, Ch.3)