Mechanism of underexcavation and practical design method for building rectification

Abstract

AbstractThis study presents the mechanism of underexcavation and practical design method for building rectification. Underexcavation is widely used to restore for not only historic monuments but also modern steel–concrete buildings that undergo large differential settlement. Due to the lack of systematic theoretical research and design specifications, the rectification process mainly depends on real-time monitoring. To meet the urgent need to address building tilt whether caused by design errors or by environmental changes, a plane strain numerical simulation is introduced to probe the mechanism of underexcavation for building rectification. The whole process of soil failure and deformation during underexcavation have been analysed with a series of numerical models, and a simplified analysis method has been proposed for predicting key parameters for the design of a building rectification. The simulation results of a single-hole excavation demonstrate the features of soil stress redistribution, the character of the displacement field, the modes of soil failure and the expansion characteristics of the failure zone. The results of simulations of multi-hole underexcavation show the relationship between plastic failure around the holes and global failure of the shallow foundation and indicate that hole closure is the main source of deformation during rectification. Based on the numerical simulation results combined with engineering experience, two key parameters of optimum spacing and hole diameter are obtained.