Slab foundation subjected to thrust faulting in dry sand: Parametric analysis and simplified design method

Motivated by recent case histories of faulting-induced damage to structures (Chi-Chi, 1999; Wenchuan 2008), this paper applies a thoroughly validated finite element analysis methodology to study the response of slab foundations subjected to thrust faulting. A parametric study is conducted, investigating the effect of key response parameters. It is shown that the stressing of the foundation, and consequently of the superstructure, stems mainly from loss of support. Depending on the geometry, loss of support takes place either under the edges or under the middle of the foundation, generating hogging or sagging deformation, respectively. Increasing the weight of the structure and/or decreasing soil stiffness leads to less stressing of the foundation. Surprisingly, even when the fault rupture emerges beyond the structure, completely avoiding the foundation, substantial foundation distress may still be generated. Exploiting the results of the parametric study, a simplified design method is developed, calling for conventional static analysis of a slab on Winkler supports, "simulating" the fault rupture by removing Winkler springs from equivalent area(s) of loss of support. The latter can be estimated with the help of design charts, further facilitating its use in practice. The proposed simplified method should not be viewed as a general design tool, but as a first idea of a practical solution to the investigated problem.