Time-domain analyses for pile deformation induced by adjacent excavation considering influences of viscoelastic mechanism

摘要

The construction of deep excavation in crowded urban cities requires effective measures to strictly control the displacements of the disturbed soil induced by excavation, in which the time behavior of excavation-soil-pile interaction mechanism obviously exists in soft clays. Many previous analytical studies for pile deformation caused by adjacent excavation are mainly based on the instantaneous behavior and provide little attention on the viscoelastic properties of surrounding soils during excavation. This paper introduces a two-stage time-domain method to predict the viscoelastic interaction between deep excavation and adjacent pile, focusing on additional stress of soil and structural deformation due to excavation-induced soil unloading. Firstly, the Mindlin's time-domain solution based on Boltzmann viscoelastic model is derived to efficiently predict the additional stress of surrounding soils at the position of adjacent pile in viscoelastic foundation. Secondly, the Pastemak's two-parameter foundation model is employed for the time-domain deformation response of adjacent pile caused by excavation unloading stress, which accounts for reological effects in viscoelastic soil. The accuracy of the two-stage time-domain method is then verified by comparisons with numerical simulation and good agreements are obtained. Finally, the parametric analyses are performed to estimate the influences of correlative coefficients in the Boltzmann viscoelastic model and paramount factors of pile on the deformation responses. In general, the two-stage time-domain method proposed in this study provides an effective insight into the excavation-soil-pile interaction considering influences of viscoelastic mechanism, which can serve as an alternative approach for conservatively estimating pile deformation tendency over time in the preliminary design of deep excavation.