Prediction of Response of Existing Building Piles to Adjacent Deep Excavation in Soft Clay

Yao-Ying Liang,Yi-Tian Chen,Nian-Wu Liu,Feng Yu,Xiao-Nan Gong

doi:10.1155/2019/8914708

Yao-Ying Liang, Yi-Tian Chen + Show 3 more

Open Access

https://doi.org/10.1155/2019/8914708

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Abstract

This study investigates building settlements near excavations in soft clay. A simplified theoretical method is proposed to predict the additional settlements and axial forces of excavation-adjacent existing building floating piles in soft clay. The soil displacement is simplified as a line or broken line along the depth direction, depending on the distance from the excavation. A hyperbolic model is applied to calculate the skin friction and tip resistance induced by the vertical soil displacement. The parameters of the hyperbolic model are corrected to fit data from in-service piles. Based on the load-transfer curve method, the additional settlements and axial forces are determined. The measured data of 17 floating piles from two excavation cases in Hangzhou, China, show good agreement with the calculated values. The results show that the position of the neutral point of the loaded pile varies with the soil settlement. Because of the upper structure, the theoretical settlements for piles near the excavation are larger than those obtained from the measured values; for distant piles, this relationship is reversed. The proposed prediction methodology is expected to guide the design of practical excavations.

Highlights

Excavations in urban spaces are gradually increasing in order to utilize the underground space for transportation infrastructure, underground shopping malls, and other engineering works. e areas of excavation have exceeded 50000 m2, and the maximum depths of these projects have exceeded 30 m; namely, the excavations have become larger, deeper, and more crowded
Is paper presents a methodology to predict the responses of existing floating piles to adjacent deep excavation in soft clay. e main achievements of the study are as follows: (1) a simplified model of excavation-induced soil displacement fields was established based on previous research and numerical simulation; (2) the parameters of the hyperbolic model were corrected to suit the existing piles; and (3) the additional settlements and axial forces were obtained using the load-transfer method. e proposed methodology was verified using data from two engineering cases, in which the deformations of the adjacent floating piles were caused by deep excavations for metro stations
Regular Deep Soil Settlement near Excavation e estimation of the soil displacement field induced by deep excavation is complex

Summary

Introduction

Excavations in urban spaces are gradually increasing in order to utilize the underground space for transportation infrastructure, underground shopping malls, and other engineering works. e areas of excavation have exceeded 50000 m2, and the maximum depths of these projects have exceeded 30 m; namely, the excavations have become larger, deeper, and more crowded. E displacement-induced skin friction and tip resistance to existing piles located near the excavation area are always calculated using hyperbolic models [9,10,11,12,13] or nonlinear models [14,15,16,17]. E main achievements of the study are as follows: (1) a simplified model of excavation-induced soil displacement fields was established based on previous research and numerical simulation; (2) the parameters of the hyperbolic model were corrected to suit the existing piles; and (3) the additional settlements and axial forces were obtained using the load-transfer method. Regular Deep Soil Settlement near Excavation e estimation of the soil displacement field induced by deep excavation is complex Such displacement is always influenced by multiple factors, including the excavation depth, descending of groundwater, characteristics of the support system, and parameters of the soil layers. The hyperbolic model is adopted to calculate the skin friction of in-service piles with corrected parameters. e original points and asymptotic values of the hyperbolic model differed for the piles that were already in service before the excavation

Unaffected soil area

Case 1

Case 2

Findings

Conclusions