Random field theory to interpret the spatial variability of lacustrine soils

The mechanical characterisation of heterogeneous soils, such as alluvial deposits, is commonly performed through a deterministic approach. This latter consists on applying the engineering judgment to choose a mean trend from continuous vertical readings of in field investigations (e.g. Cone Penetration Tests - CPTs) or discontinuous ones as Standard Penetration Tests (SPTs). Conversely, in order to take into account the spatial variability of mechanical measurements of the soil the spatial standard deviation, the scale of fluctuation and the autocorrelation function have to be calculated. This latter approach follows the stochastic field theory and it can be fruitfully applied to all those soil formations that are inherently heterogeneous. In this paper, theoretical bases of this approach has been briefly described and a practical application to lacustrine soil deposits at Popoli site located in Abruzzi Region (Italy) are presented. The methods introduced are not straightforward but they provide information that can be used to improve both the reliability of the geotechnical design and the efficiency of the soil use depending on the investigated depths and the measurement intervals.