3D finite element analysis of pile responses to adjacent excavation in soft clay: Effects of different excavation depths systems relative to a floating pile

• Published in: Tunnelling and underground space technology Vol. 86; pp. 138 - 155
• Main Authors: Soomro, Mukhtiar Ali, Mangnejo, Dildar Ali, Bhanbhro, Riaz, Memon, Noor Ahmed, Memon, Muneeb Ayoub
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2019; Elsevier BV; Elsevier
• Subjects: Axial loads; Bending; Bending moments; Boundary conditions; Case depth; Centrifuges; Civil Engineering; Clay; Computer simulation; Constitutive models; Engineering Sciences; Excavation; Excavation depths systems; Finite element analysis; Finite element method; Géotechnique; Lateral displacement; Load distribution (forces); Mathematical models; Pile settlement; Single pile; Soft clay; Soft ground; Stiffness; Stress concentration; Single pile; Finite element analysis; Excavation depths systems; Soft clay
• ISSN: 0886-7798; 1878-4364
• DOI: 10.1016/j.tust.2019.01.012

To gain new insights into single pile responses to adjacent excavations in soft ground, three dimensional numerical parametric studies are carried out. An advanced hypoplastic (clay) constitutive model which takes account of small-strain stiffness is adopted. The effects of excavation depths (He) relative to pile (Lp) were investigated by simulating the excavation near the pile shaft (i.e., He/Lp = 0.67), next to (He/Lp = 1.00) and below the pile toe (He/Lp = 1.33). In addition, the effect of pile head boundary conditions and different working loads with FOS = 3.0 and 1.5 were also studied. The model parameters are calibrated and validated against measured results in centrifuge reported in literature. It is found that the pile responses to excavation depend upon formation level of the excavation as well as the embedded depth of the wall. With different wall depth in each case, the induced settlement, lateral displacement and bending moment in the pile at the same stage of the excavation was different in the three cases. Among the three cases, the excavation in case of He/Lp = 1.33 resulted in the largest pile settlement (i.e., 7.6% pile diameter). On the other hand, the largest pile deflection was induced in case of He/Lp = 0.67. On contrary, insignificant bending moment and changes in axial load distribution induced in the pile on completion of the excavation in each case. However, significant bending moment (60% of pile BM capacity of 800 kNm) induced in the pile with fixed head condition. The different working loads (with FOS = 3.0 and 1.5) influence induced pile settlement but have relatively minor effect on induced bending moment.