Rectangular mudmat foundations for subsea structures are commonly designed according to ISO and API guidelines. However, the modern trend towards deeper waters and heavier structures is currently challenging traditional approaches to foundation design, especially in presence of particularly poor soil conditions. The intrinsic conservatism carried by design codes may not only lead to higher fabrication/installation costs, but also conflict w ith the operational limits of existing installation vessels. Based on the analysis of four design cases, it is argued that ISO/API safety factors may be from 1.5 to 2.3 times as low as the predictions of elastoplastic finite element (FE) simulations. Such a conservatism is also found to considerably increase with the embedment depth, whereas the influence of the foundation aspect ratio is nearly negligible. A simple calculation example shows that the systematic use of numerical analysis in design may result in a 47% reduction of the total foundation area, and an overall decrease in fabrication costs of approximately 16%. ... Read more

Contaminant leaks released from landfills are a threat to groundwater quality. The groundwater monitoring systems installed in the vicinity of such facilities are vital. In this study the detection probability of a contaminant plume released from a landfill has been investigated by means of both a simulation and an analytical model for both homogeneous and heterogeneous aquifer conditions. Since the detection probability is a sensitive quantity, we first compare the two methods for homogeneous aquifer conditions to assess the errors that are encountered by performing simulations. The analysis shows that the simulation model yields the detection probabilities of a contaminant plume at a given monitoring well quite well in the homogeneous case. For heterogeneous aquifers we apply the approximated analytical model based on macro-dispersivities. Here we find that this model is insufficient in monitoring system design, since the obtained analytical values of the detection probabilities at a given monitoring well differ significantly from those computed by simulation. ... Read more