Allowable wall deflection of braced excavation adjacent to pile-supported buildings

Abstract

To protect adjacent buildings is a major concern for the construction of excavation in urban areas. In practice, the impacts on neighboring pile-supported buildings are normally minimized by limiting the deflection of earth retaining wall. Existing deflection criteria, however, are often empirical. In this work, we employ an analytical model to relate the wall deflection of braced excavation to the response of adjacent pile-supported buildings and thus forming a theoretical tool for determining the allowable deformation of excavation support structures based on the tolerance of buildings to distortion. The model combines closed-form excavation-induced free-field soil movements with elastic continuum solution that explicitly accounts for the interactions between raft, piles, and soils. Following validation against field model test and finite element simulation, the model is utilized to reveal the correspondence between the angular distortion of pile-supported buildings and the maximum retaining wall deflection under different combinations of excavation geometry, soil properties, and parameters of pile foundation potentially encountered in practice. A dimensionless factor composed of these influencing variables is proposed, and its correlation with the ratio of the building angular distortion over the maximum retaining wall deflection provides a rational way to determine the serviceability limit states of braced excavation.