Building Construction Handbook, Eighth Edition

Site Investigation ~ this is an all embracing term covering every

aspect of the site under investigation.

Soil Investigation ~ specifically related to the subsoil beneath the

site under investigation and could be part of or separate from the

site investigation.

Purpose of Soil Investigation ~

1. Determine the suitability of the site for the proposed project.

2. Determine an adequate and economic foundation design.


3. Determine the difficulties which may arise during the construction
   process and period.


4. Determine the occurrence and/or cause of all changes in
   subsoil conditions.

The above purposes can usually be assessed by establishing the

physical, chemical and general characteristics of the subsoil by

obtaining subsoil samples which should be taken from positions on

the site which are truly representative of the area but are not

taken from the actual position of the proposed foundations. A

series of samples extracted at the intersection points of a 20„000

square grid pattern should be adequate for most cases.

Soil Samples ~ these can be obtained as disturbed or as

undisturbed samples.

Disturbed Soil Samples ~ these are soil samples obtained from

bore holes and trial pits. The method of extraction disturbs the

natural structure of the subsoil but such samples are suitable for

visual grading, establishing the moisture content and some

laboratory tests. Disturbed soil samples should be stored in

labelled airtight jars.

Undisturbed Soil Samples ~ these are soil samples obtained using

coring tools which preserve the natural structure and properties of

the subsoil. The extracted undisturbed soil samples are labelled and

laid in wooden boxes for dispatch to a laboratory for testing. This

method of obtaining soil samples is suitable for rock and clay

subsoils but difficulties can be experienced in trying to obtain

undisturbed soil samples in other types of subsoil.

The test results of soil samples are usually shown on a drawing

which gives the location of each sample and the test results in the

form of a hatched legend or section.

Soil Investigation