Effect of embedment and spacing of cojoined skirted foundation systems on undrained limit states under general loading.

A foundation system may involve more than a single footing with an arrangement such that the footings are sufficiently closelyspaced that adjacent footings interact. Vertical, horizontal, and moment capacity of multifooting foundation systems are potentiallydependent on footing interaction, and in particular overturning capacity can be significantly enhanced by the structural rigidity of amultifooting foundation system. There is no established procedure for the calculation of bearing capacity of a shallow foundation systemcomprising cojoined footings and ad hoc approaches may simply involve summing the ultimate limit states of the individual footings asif they acted independently; neglecting additional capacity of the system available from the kinematic constraint provided by the structuralconnection between the footings. Plane strain finite-element analyses have been carried out to investigate the undrained ultimate limitstates under general loading of skirted two-footing foundation systems at various normalized spacing compared to a single skirted footingof equal bearing area and embedment ratio.