Characterising site investigation performance in multiple-layer soils and soil lenses

Abstract

ABSTRACT Insufficient or inappropriate soil testing can lead to a range of undesirable consequences, however there is little research available on site investigation performance in complex soils. The present study analyses the relationship between investigation quality and various soil conditions, such as the number of layers and the presence of lenses. Investigation performance is assessed through the use of random, virtual soils in a Monte Carlo analysis context. The assessment metric is total expected project cost, which implicitly incorporates the risk of damage from poor investigation. It is shown that the optimal investigation can save in the order of up to AUD$ 2 million (£1.1 million), for a 6-storey, 400 m2 building supported by 9 piles, or 30% of its construction cost. The optimal number of boreholes was found to vary with the lens stiffness ratio, lens thickness, and the magnitude of variability of both the layer boundaries and soil properties.