Physical modelling of cyclic loading induced footing settlement with a nearby pit excavation

Abstract

A series of physical model tests and cyclic triaxial tests were performed on a dry sand to investigate the effects of excavating an adjacent pit on the settlement behaviour of a footing under cyclic loading. The excavation is simulated by moving a retaining wall between loading cycles in the physical model tests. The excavation induced stress disturbance on soil elements is modelled by reducing cell pressure between loading cycles in triaxial tests. The results indicate that nearby excavation leads to reduction in lateral stress in ground and therefore increases the settlement of footing in the subsequent loading cycles. However, there is no clear relationship between the settlement increment and the magnitude of wall movement, when the lateral movement of the wall is within the range of 0.1% to 0.37% of the wall height. The lateral excavation does not have great impact on the influence zone of the footings under cyclic loading. An empirical model is proposed to estimate the cyclic loading-induced strain accumulation of sand with the consideration of lateral unloading effects between loading cycles. After being validated using cyclic triaxial tests results, the proposed model is employed to predict cyclic loading-induced settlement of the footing before and after the excavation.