Effects of Mobilized Wall Friction Angle on Resultant Seismic Earth Pressure on Shallow Foundation

Abstract

To investigate the seismic earth pressure on a shallow foundation, a dynamic centrifuge test using a sinusoidal sweep motion was performed on a superstructure–footing model embedded in dry sand deposits. The resultant seismic earth pressure and vertical wall friction acting on the plates on the active and passive sides were separately measured using two-dimensional load cells. The shapes of the measured hysteresis loops of earth pressure and relative displacement varied with the input motion period. The amplitude of the earth pressure depended on the mobilized wall friction angle rather than on the soil acceleration. A key factor for the hysteresis-loop shape was the phase difference between a peak of the mobilized wall friction angle and that of the relative displacement. The mobilized wall friction angles were dependent on the overturning moment caused by the superstructure inertia. When the relative displacement was mainly caused by the soil displacement, the phase between the relative displacement and the wall friction angle could be large. The earth pressure did not peak at a peak in the relative displacement.