Influence of site investigation borehole pattern and area on pile foundation performance

Site investigations are the largest element of technical and financial risk in civil engineering works, with insufficient testing often causing cost over-runs, construction delays, foundation failure and over-design. However, there is little research on where best to place boreholes with respect to the foundation. Typically, if the structure location is known, then boreholes are placed at the centre, or otherwise at the corners, although some studies indicate that there may be benefit to randomising the sampling location. This study aims to determine the best of a series of sampling schemes, where each scheme involves varying degrees of randomness, as well as to examine the effect of investigation area relative to the building footprint.

The optimal sampling scheme is determined from Monte Carlo analysis, where a random, variable, single layer, 3D virtual soil is generated. From this, it is possible to carry out a variety of virtual site investigations, determine true foundation performance, and determine the magnitude of structural damage resulting from insufficient investigation. Total cost, calculated from a combination of construction, investigation, and failure costs, is used as the objective function to be minimised.