Three-dimensional numerical analyses of pile responses to tunneling-induced ground movements in bilayer soil

• Published in: World journal of engineering 2024-01, Vol.21 (1), p.71-90
• Main Authors: Houhou, Mohamed Nabil, Amari, Tamir, Belounar, Abderahim
• Format: Article
• Language: English
• Subjects: Aluminum; Axial forces; Axial loads; Bending moments; Deflection; Diameters; Ground motion; Internal forces; Mathematical models; Maximum bending; Mohr-Coulomb theory; Numerical analysis; Numerical methods; Numerical models; Pile foundations; Pile groups; Pile settlement; Plane strain; Research methodology; Shear strength; Soil analysis; Soil layers; Soil stresses; Soils; Steel alloys; Stiffness; Strain gauges; Three dimensional analysis; Three dimensional models; Tunneling shields
• ISSN: 1708-5284; 2515-8082; 1708-5284
• DOI: 10.1108/WJE-04-2022-0159

Purpose This paper aims to investigate the responses of single piles and pile groups due to tunneling-induced ground movements in a two-layered soil system. The analyses mainly focus on the additional single pile responses in terms of bending moment, lateral deflection, axial force, shaft resistance and pile settlement. Subsequently, a series of parametric studies were carried out to better understand the responses of single piles induced by tunneling. To give further understanding regarding the pile groups, a 2 × 2 pile group with two different pile head conditions, namely, free and capped, was considered. Design/methodology/approach Using the PLAXIS three-dimensional (3D) software, a full 3D numerical modeling is performed to investigate the effects of ground movements caused by tunneling on adjacent pile foundations. The numerical model was validated using centrifuge test data found in the literature. The relevance of the 3D model is also judged by comparison with the 2D plane strain model using the PLAXIS 2D code. Findings The numerical test results reveal that tunneling induces significant displacements and internal forces in nearby piles. The magnitude and distribution of internal forces depend mainly on the position of the pile toe relative to the tunnel depth and the distance between the pile and the vertical axis of the tunnel. As the volume loss increases from 1% to 3%, the apparent loss of pile capacity increases from 11% to 20%. By increasing the pile length from 0.5 to 1.5 times, the tunnel depth, the maximum pile settlement and lateral deflection decrease by about 63% and 18%, respectively. On the other hand, the maximum bending moment and axial load increase by about 7 and 13 times, respectively. When the pile is located at a distance of 2.5 times the tunnel diameter (Dt), the additional pile responses become insignificant. It was found that an increase in tunnel depth from 1.5Dt to 2.5Dt (with a pile length of 3Dt) increases the maximum lateral deflection by about 420%. Regarding the interaction between tunneling and group of piles, a positive group effect was observed with a significant reduction of the internal forces in rear piles. The maximum bending moment of the front piles was found to be higher than that of the rear piles by about 47%. Originality/value Soil is a complex material that shows differently in primary loading, unloading and reloading with stress-dependent stiffness. This general behavior was not possibly being accounted