ABSTRACT
Constant total stress foundations are a special class of geotechnical problems in which the total load transmitted by the foundation is assumed constant, and in which water table fluctuations (below the ground surface) change effective stress, hence leading to possible settlements (when the water table descends) or heave of the foundation (when it ascends).
We address a particular case of this problem, in which a building with a diaphragm wall foundation is planned at a site in which a high permeability gravel layer, that is hydraulically connected to a nearby river, overlays a fine-grained stratum with lower permeability. We analyze how transient water table ascensions (associated, for instance, to the design flood for a given return period) affect the effective stress at the base slab of the building, with particular attention to the number of days that such high water levels must be kept at higher-than-normal elevations so as to produce likely foundation problems. The geotechnical and flow problems are solved using a finite element code and, to be able to assess the influence of existing uncertainties on the computed results, we conduct a reliability analysis of the problem using the simplified procedure recommended by the Spanish Recommendations for the Design of Maritime and Harbour works. Finally, we conduct a sensitivity analysis to assess the influence of the main geometric variables associated to the diaphragm wall design on the computed results.
