Influence of fabric anisotropy on seismic response of circular foundation

Abstract

Earthquake induced foundation failure has occurred in a number of events worldwide, such as the 1964 Niigata earthquake and 1995 Kobe earthquake. Fabric anisotropy has been considered as one of the factors that affect liquefaction characteristics. In this study, dynamic centrifuge tests were conducted for studying the influence of sand fabric anisotropy on seismic response of circular foundations. For this purpose, sub-angular Toyoura sand was used as the most anisotropic material, while sub-rounded Nevada sand was used for the comparison tests. Each group of tests were carried out in both dry and saturated conditions.These tests are considered complementary to similar centrifuge tests that the authors performed using rectangular foundations. The tests show that sand fabric anisotropy has significant impact on the seismic response of circular foundations as well, especially in saturated conditions. Specifically, as the deposition angle of the sand layer increased, the data show a remarkable decrease in acceleration amplitude concurrently with a considerable decrease of pore pressure ratio and foundation settlement. These effects were more pronounced in the sub-angular Toyoura sand. These effects of increased deposition angle are consistent with the corresponding decrease of bearing capacity and increase of footing settlements in static centrifuge tests from the literature.