Response of shaft friction along existing piles to deep excavation
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ORIGINAL PAPER
Response of shaft friction along existing piles to deep excavation Feng Yu . Hai-lei Kou . Yao-bo Guo . Zheng-bing Xie
Received: 14 July 2018 / Accepted: 12 November 2020 Ó Springer Nature Switzerland AG 2020
Abstract Excavation following the installation of pile may significantly affect the original behavior of installed piles. To better understand the shaft friction response of existing piles during deep excavation, the principle of pile loading transfer was discussed in this study. Based on the concept of interface normal stress and interface relative displacement, a 5-segment distribution pattern of pile shaft friction was proposed. The varying law and practical calculation model of shaft friction subject to deep excavation was also proposed through numerical analysis. Its feasibility was verified against case histories and this could provide possible reference to pile design incorporating excavation effect. Keywords Deep excavation Interface normal stress Relative displacement Shaft friction Numerical analysis
F. Yu Y. Guo Z. Xie School of Civil Engineering and Architecture, Zhejiang Sci-Tech University, Hangzhou 310018, China H. Kou (&) College of Engineering, Ocean University of China, Qingdao 266000, China e-mail: [email protected]
1 Introduction In the process of pile and related excavation, the piles are usually installed firstly and the subsequent deep excavation is conduced, which would have a large impact on the existing pile. Iwasaki et al. (Iwasaki et al. 1994) indicated that the soil unloading and rebound during excavation would affect the forces distribution on pile. Zhu and Sun (Huogen and Jiaping 2006) analyzed an engineering example that an engineering pile was tensioned to crack caused by deep excavation. During excavation, the soil stress at excavation face released and rebounded, which derived the pile up. The upper part of the pile bears the upward positive friction effect and the lower part would prevent the pile moving up, producing a downward negative friction effect. Hu et al. (Qi et al. 2008), Luo (Yao-wu 2010) and Du et al. (Yiming et al. 2014) discussed the bearing behavior of pile after excavation from the perspective of stress path, soil over-consolidation and compression of pile shaft, respectively. However, how to evaluate the distribution of shaft friction of existing piles caused by deep excavation is still inconclusive. Thus, it is hard to consider the excavation effect on pile design which would be faced in the real construction phase. On the other hand, the construction of underground space based on existing pile-raft foundation, which emerged in recent years, also meet the same problem. The major difference between this and new construction is that the pile top is not no-load condition before
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Geotech Geol Eng
excavation and has been in the state of working load. At this point, the urgency of considering the mechanics behaviors of existing pile during excavation in design is more obvious. In
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