Geomechanics and Engineering

Techno-Press (테크노프레스)
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)
  • Received : 2022.07.18
  • Accepted : 2022.09.14
  • Published : 2022.10.10
⟨ Previous Next ⟩

Abstract

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.

Keywords

Acknowledgement

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

References

  1. Fang, J., Kong, G. and Yang, Q. (2022), "Group performance of energy piles under cyclic and variable thermal loading", J. Geotech. Geoenviron. Eng., 148(8), 04022060. https://doi.org/10.1061/(ASCE)GT.1943-5606.0002840.
  2. Finno, R.J., Lawrence, S.A., Allawh, N.F. and Harahap, I.S. (1991), "Analysis of performance of pile groups adjacent to deep excavation", J. Geotech. Eng., 117(6), 934-955. https://doi.org/10.1061/(ASCE)0733-9410(1991)117:6(934).
  3. Goh, A.T.C., Wong, K.S., Teh, C.I. and Wen, D. (2003), "Pile response adjacent to braced excavation", J. Geotech. Geoenviron. Eng., 129(4), 383-386. https://doi.org/10.1061/(ASCE)1090-0241(2003)129:4(383).
  4. Gudehus, G. (1996), "A comprehensive constitutive equation for granular materials", Soil. Found., 36(1), 1-12. https://doi.org/10.3208/sandf.36.1.
  5. Herle, I. and Gudehus, G. (1999), "Determination of parameters of a hypoplastic constitutive model from properties of grain assemblies", Mech. Cohes.-Frict. Mater.: J. Exper., Model. Comput. Mater. Struct., 4(5), 461-486. https://doi.org/10.1002/(sici)1099-1484(199909)4:5%3C461::aid-cfm71%3E3.0.co,2-p.
  6. Hibbitt, Karlsson, Sorensen (2010), Abaqus User's Manual, Version 6.10.2, Hibbitt, Karlsson & Sorensen Inc., Providence, RI, USA.
  7. Ishihara, K. (1993), "Liquefaction and flow failure during earthquakes", Geotechnique, 43(3), 351-415. https://doi.org/10.1680/geot.1993.43.3.351.
  8. Jaky, J. (1944), "The coefficient of earth pressure at rest", J. Soc. Hungarian Arch. Eng., 355-358. (in Hungarian)
  9. Karira, H., Kumar, A., Ali, T.H., Mangnejo, D.A. and Mangi, N. (2022), "A parametric study of settlement and load transfer mechanism of piled raft due to adjacent excavation using 3D finite element analysis", Geomech. Eng., 30(2), 169-185. https://doi.org/10.12989/gae.2022.30.2.169.
  10. Korff, M., Mair, R.J. and Van Tol, F.A. (2016), "Pile-soil interaction and settlement effects induced by deep excavations", J. Geotech. Geoenviron. Eng., 138(7), 04016034. https://doi.org/10.1061/(ASCE)GT.1943-5606.0001434.
  11. Lee, S.W. (2019), "Experimental study on effect of underground excavation distance on the behavior of retaining wall", Geomech. Eng., 17(5), 413-420. https://doi.org/10.12989/gae.2019.17.5.413.
  12. Liyanapathirana, D.S. and Nishanthan, R. (2016), "Influence of deep excavation induced ground movements on adjacent piles", Tunnel. Undergr. Space Technol., 52, 168-181. https://doi.org/10.1016/j.tust.2015.11.019.
  13. Maeda, K. and Miura, K. (1999), "Relative density dependency of mechanical properties of sands", Soil. Found., 39(1), 69-79. https://doi.org/10.3208/sandf.39.69.
  14. Ng, C.W., Shakeel, M., Wei, J. and Lin, S. (2021), "Performance of existing piled raft and pile group due to adjacent multipropped excavation: 3D centrifuge and numerical modeling", J. Geotech. Geoenviron. Eng., 147(4), 04021012.. https://doi.org/10.1061/(ASCE)GT.1943-5606.0002501.
  15. Ng, C.W., Wei, J., Poulos, H. and Liu, H. (2017), "Effects of multipropped excavation on an adjacent floating pile", J. Geotech. Geoenviron. Eng., 143(7), 04017021. https://doi.org/10.1061/(ASCE)GT.1943-5606.0001696.
  16. Niemunis, A. and Herle, I. (1997), "Hypoplastic model for cohesionless soils with elastic strain range", Mech. Cohes.-Frict. Mater.: J. Exper., Model. Comput. Mater. Struct., 2(4), 279-299. https://doi.org/10.1002/(SICI)1099-1484(199710)2:4<279::AID-CFM29>3.0.CO,2-8.
  17. Poulos, H.G. (2001), "Piled raft foundations: Design and applications. Geotechnique, 51(2), 95-113. https://doi.org/10.1680/geot.2001.51.2.95.
  18. Shi, J., Chen, Y., Lu, H., Ma, S. and Ng, C.W.W. (2022a), "Centrifuge modeling of the influence of joint stiffness on pipeline response to underneath tunnel excavation", Can. Geotech. J., 59(9), 1. https://doi.org/10.1139/cgj-2020-0360.
  19. Shi, J., Wei, J., Ng, C. W. and Lu, H. (2019), "Stress transfer mechanisms and settlement of a floating pile due to adjacent multi-propped deep excavation in dry sand", Comput. Geotech., 116, 103216. https://doi.org/10.1016/j.compgeo.2019.103216.
  20. Shi, J., Wei, J., Ng, C.W., Lu, H., Ma, S., Shi, C. and Li, P. (2022b), "Effects of construction sequence of double basement excavations on an existing floating pile", Tunnel. Undergr. Space Technol., 119, 104230. https://doi.org/10.1016/j.tust.2021.104230.
  21. Soomro, M.A., Kumar, M., Mangi, N., Mangnejo, D.A. and Cui, Z.D. (2022b), "Parametric study of twin tunneling effects on piled foundations in stiff clay: 3D finite-element approach", Int. J. Geomech., 22(6), 04022079. https://doi.org/10.1061/(ASCE)GM.1943-5622.0002386.
  22. Soomro, M.A., Liu, K., Mangnejo, D.A. and Mangi, N. (2022c), "Effects of twin excavations with different construction sequence on a brick masonry wall: 3D finite element approach", Struct., 41, 866-886. https://doi.org/10.1016/j.istruc.2022.05.060.
  23. Soomro, M.A., Mangi, N., Memon, A.H. and Mangnejo, D.A. (2022a), "Responses of high-rise building resting on piled raft to adjacent tunnel at different depths relative to piles", Geomech. Eng., 29(1), 25-40. https://doi.org/10.12989/gae.2022.29.1.025.
  24. Soomro, M.A., Mangnejo, D.A., Saand, A. and Hong, Y. (2021a), "Responses of a masonry facade to multi-propped deep excavation-induced ground deformations: 3D numerical parametric study", Eur. J. Environ. Civil Eng., 1-29. https://doi.org/10.1080/19648189.2021.1926336.
  25. Soomro, M.A., Mangnejo, D.A., Saand, A. and Mangi, N. (2021c), "3D numerical analysis of a masonry facade subjected to excavation-induced ground deformation", Int. J. Geotech. Eng., 16(7), 865-877. https://doi.org/10.1080/19386362.2021.1937853.
  26. Soomro, M.A., Mangnejo, D.A., Saand, A., Mangi, N. and Auchar Zardari, M. (2021b), "Influence of stress relief due to deep excavation on a brick masonry wall: 3D numerical predictions", Eur. J. Environ. Civil Eng., 1-24. https://doi.org/10.1080/19648189.2021.2004450.
  27. Soomro, M.A., Saand, A., Mangi, N., Mangnejo, D.A., Karira, H. and Liu, K. (2021d), "Numerical modelling of effects of different multipropped excavation depths on adjacent single piles: Comparison between floating and end-bearing pile responses", Eur. J. Environ. Civil Eng., 25(14), 2592-2622. https://doi.org/10.1080/19648189.2019.1638312.