Settlement analysis of residential buildings with eccentric loads and complex subsoil conditions

In the present paper, an analysis is performed on the movements undergone by some residential buildings in 1983, during their construction. A common feature of these buildings is an asymmetric superstructure that makes the vertical loads acting on the foundations highly eccentric. A sloping ground surface and a complex subsoil condition, characterised by the presence of strongly inclined layers of compressible soils, were other predisposing factors for the observed movements. The buildings underwent a significant rigid rotation (tilt) to the extent that their serviceability was compromised because of the resulting floor inclination. As a consequence, construction was suspended and a subsurface investigation consisting of boreholes, cone penetration tests and conventional laboratory tests was performed. In addition, the vertical displacement of some representative points of the building foundations was measured during a period of about 1 year. A finite-element analysis of the building displacements is carried out in the present study to highlight the different roles played by load eccentricity, soil layering and a sloping ground surface in causing the observed building movements. To restore the serviceability of the buildings, their foundations were underpinned with micropiles, some of which were pre-stressed. The effectiveness of this measure is also analysed.