Geomechanics and Engineering

  • 제31권1호
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  • Pages.53-69
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  • 2022
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  • 2005-307X(pISSN)
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  • 2092-6219(eISSN)
테크노프레스 (Techno-Press)
권호 표지
DOI QR코드

DOI QR Code

Numerical investigation of responses of a piled raft to twin excavations: Role of sand density

  • Karira, Hemu (Department of Civil Engineering, Mehran University of Engineering and Technology, Shaheed Zulfiqar Ali Bhutto Campus) ;
  • Kumar, Aneel (Department of Civil Engineering, Mehran University of Engineering and Technology) ;
  • Ali, Tauha Hussain (Department of Civil Engineering, Mehran University of Engineering and Technology) ;
  • Mangnejo, Dildar Ali (Department of Civil Engineering, Mehran University of Engineering and Technology, Shaheed Zulfiqar Ali Bhutto Campus) ;
  • Yaun, Li (School of Mechanics and Civil Engineering, China University of Mining and Technology)
  • 투고 : 2022.07.18
  • 심사 : 2022.09.14
  • 발행 : 2022.10.10
⟨ 이전 논문 다음 논문 ⟩

초록

In densely built areas, the development of underground transportation systems often involves twin excavations, which are sometimes unavoidably constructed adjacent to existing piled foundations. Because soil stiffness degrades with induced stress release and shear strain during excavation, it is vital to investigate the piled raft responses to subsequent excavation after the first tunnel in a twin-excavation system. The effects of deep excavations on existing piled foundations have been extensively investigated, but the influence of twin excavations on a piled raft is seldom reported in the literature. In this study, three-dimensional numerical analyses were carried out to investigate the influence of sand density on an existing piled raft (with a working load on top of the raft) due to twin excavations. A wide range of relative density (Dr) from loosest (30%), loose to medium (50% and 70%), and densest (90%) were selected to investigate the effects on settlement and load transfer mechanism of the piled raft during twin excavations. An advanced hypoplastic sand model (which can capture small-strain stiffness and stress-state dependent dilatancy of sand) was adopted. The model parameters are calibrated against centrifuge test results in sand reported in the literature. From the computed results, it is found that twin excavations in loose sand (Dr=30%) caused the most significant settlement. This is because of the higher stiffness of denser sand (Dr=90%) than that of loose sand. In contrast, a much larger tilting (maximum magnitude=0.18%) was computed in dense sand than in loose sand after the completion of the first excavation. As far as the load transfer mechanism along the piles is concerned, an upward load transfer to mobilize shaft resistance is observed in loose sand. On the contrary, a downward load transfer is observed in dense sand.

키워드

과제정보

The authors would like to acknowledge the financial support provided by Mehran University of Engineering & Technology, Jamshoro, Sindh and Pakistan.

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