Kevin, this is largely unfinished with some of the journals which I have written about not being relevant. My main basis of literature review will be on Terzaghi, vesic, a thesis, and lau and Bolton.
Terzaghi, K. (1943). Theoretical soil mechanics. New York: Wiley
In this book, Terzaghi introduces the idea of bearing capacities, the critical load over a given area which a soil takes to fail. The concept of bearing capacities became fundamental in determining the ultimate load which can be taken. Once a soil is pushed beyond its elastic region, it undergoes plastic deformation and fails after a given settlement.
Terzaghi developed a simple equation which calculated the ultimate bearing capacity of a soil which was dependent on the soils’ properties and the loading conditions.
The first term takes into account the effect of the cohesion of the soil, the second term for the surcharge on the soil and the third term for the self-weight of the soil. All of the factors of Nq Nc Nγ are derived from the friction angle of the soil.
Terzaghi had developed the equation from model testing of a strip foundation, defining the depth of the foundation to be infinite relative to the width. One of the limitations with Terzaghi’s ultimate bearing capacity was adapting it to other situations. The equation did not take into account different shaped foundations, inclined loads and different depths of foundations. Some of the assumptions made by Terzaghi are incorrect and have not been dealt with. The assumption of a homogeneous soil is incorrect in the majority of cases and for my following experiment; the presence of bedrock does not fit in line with Terzaghi’s eqaution.
Analysis of ultimate loads of shallow foundations, Vesic 1973
Vesic developed Terzaghi’s bearing capacity theory through more model testing. In the experiment, the load placed upon the model footing was plotted against the settlement measured on a graph.