Some level of geotechnical knowledge is necessary for all structural design jobs as all structures involve loads being transmitted to the ground. Ideally it is desirable to carry out some level of investigation to determine ground conditions where any change in loading on the ground takes place, but often this work can be omitted in a desire to save money, especially during times of economic slowdown.
Our experience has given us detailed knowledge of local ground conditions. We can often use this together with the use of local geological and soil maps to give clients initial advice on likely ground conditions for a site and the likely foundation types that will be required, and when for areas of likely poor ground conditions and for all larger schemes, geotechnical ground investigations are essential we can arrange the following:-
In house hand auger / mackintosh probe investigations which are ideal for small scale schemes and give low cost information about a limited area with minimal disruption (ideal for extensions, garden severance plots etc.) In some ground conditions e.g. made ground with bricks or dense gravel this equipment cannot be used.
JCB excavated trail pits are ideal for larger sites where shallow footings are anticipated and can give good information on ground up to 4 metres deep. Many pits can be excavated rapidly though there will be some disruption to the site simply getting the excavator into position and further disruption from the excavation of the pits.
Specialist shell and auger boreholes and other techniques e.g. window sampling and dynamic probing can give information about the ground at depth required for the design of bored piles or ground improvement techniques.
This short article gives an overview of the common factors governing foundation design of residential or small commercial buildings in East Anglia and a summary of commonly used foundation types.
Most of East Anglia is relatively flat and is composed of either sands or clays with adequate capacity to withstand the loads imposed on them by low rise buildings, so on the face of it most foundation design in this part of the world should not be particularly onerous and this is indeed the case with the simple approach of digging a trench 1 metre deep and filling it with concrete, sufficing in most cases. However in the following cases this is not sufficient and special foundations can be needed.
With all of these, alternatives to conventional foundations can be required and we can provide designs for a variety of special foundation types to cover these situations.