Parameters Affecting the Interaction of Shallow Embedded Foundations and Reverse Faulting

Observations after the 1999 Turkey and Taiwan earthquakes and the 2008 China earthquake have indicated that the structures experience different levels of damages induced by faulting dislocation. Numerous studies have been conducted on the most common types of foundations such as shallow foundations, pile and caisson foundations subjected to faulting by means of numerical and experimental investigations. The parameters affecting the interaction of a reverse fault rupture with a shallow embedded foundation have been investigated by experimentally validated numerical models using ABAQUS software. These parameters are the embedment depth of foundation, the bearing pressure of foundation, the rigidity of foundation and the foundation position. The reverse fault rupture at a dip angle of 60° propagates in a moderately dense sand layer and interplays with the embedded foundation. A summary of conclusions is as follows:

The behavior of foundation and the development of rupture mechanisms are fully dependent on the location of the foundation relative to the fault rupture and the magnitude of the fault offset. Depending on the foundation position, the loss of support of the foundation takes place either under the edges (i.e. the hogging deformation) or under the middle (i.e. the sagging deformation) of the foundation. The foundation experiences the loss of support and stressing even for the indirect-hit case when the fault rupture emerges outside the foundation width.
The increase of the weight of the foundation leads to diverting the fault rupture and less stressing of the foundation. However, the rotation of foundation depends strongly on the foundation position relative to the fault outcrop compared to the weight of the foundation. By increasing the embedment depth of the foundation, the weight of the foundation has no beneficial effect for the behavior of shallow foundation and the kinematic constraint of deeper foundation causes to significantly increase the rotation of the embedded foundations.
As the embedment depth increases, the rotation of the foundation decreases for the same rupturing mechanism. It can be attributed to the similar performance of a deeper shallow embedded foundation to that of a deep foundation (such as a caisson foundation). However, the rotation of the foundations with the different embedment depths is largely dependent on the position of the foundation relative to the outcropping fault rupture and the magnitude of the fault offset. Also, the results show that the different fault-induced mechanisms such as footwall, gapping and hanging wall may happen depending on the magnitude of fault offset for a given embedment depth and position of the foundation.
Depending on the rigidity of the foundation, the rigid shallow foundation may diffuse/divert the fault rupture beyond the foundation, whereas by contrast with a flexible foundation, the fault rupture will develop as a distinct rupture and strike the foundation underneath. In all cases, the foundation rigidity is an important parameter controlling the stressing of the foundation. Decreasing the rigidity of the foundation causes to increase the normalized bending moment of the foundation and the foundation may experience substantial distress. The results indicate that rigid shallow foundations are more suitable than flexible ones for a structure subjected to a major reverse fault rupturing underneath.