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    Item type:Publication,
    Structural Responses of a Tunnel Lining Due to an Adjacent Loaded Pile
    (2023-06-01) ;
    Jongpradist, Pornkasem
    ;
    Jongpradist, Pattaramon
    ;
    Schweiger, Helmut F.
    The work reported in this article numerically investigates the structural forces in a tunnel lining after applying an adjacent loaded pile for varying pile tip positions considering the tunnel and soil stratum. Analysis reveals that the structural responses are strongly associated with the distorted elliptical shape of the deformed tunnel, which depends on the relative position of the pile tip with respect to the tunnel crown. The change in bending moment in the tunnel lining is of greater concern than the change in the axial force of the tunnel lining. Although the maximum change in structural forces can be up to 115% of the initial value, assessment in terms of maximum change in the structural forces is unsuitable. This is because the maximum change does not occur at the location that has large initial forces. The total combined bending moment and axial force in the lining at the tunnel spring line and in the tunnel invert zone are recommended for cases where the pile tip level is at the tunnel spring line and cases with the deepest possible pile tip elevation, respectively, for the assessment.
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    Item type:Publication,
    INVESTIGATION OF TUNNEL RESPONSE DUE TO THE EFFECT OF ADJACENT LOADED PILE ROW BY 3D SIMULATION ANALYSIS
    (2022-09-01)
    Heama, Narunat
    ;
    The construction of tunnels for transportation, wastewater, electricity, etc., in the major cities has flourished. In the meantime, other infrastructures such as elevated trains, and flyovers, are continually constructed for urbanization. Under a soft ground condition, they are supported by the pile foundations required pile rows which are possibly located along the existing tunnel. A common challenge encountered in the loaded pile row of the new adjacent structures is inevitably inducing soil stress changes and deformation of existing tunnels. Thus, an assessment of the impact of pile underloading on the integrity of the existing tunnels is essential. The three-dimensional finite element analyses (3D FEA) with two pile conditions were carried out. The tunnel responses (transversal deformation and additional forces) at different transverse sections are presented. The maximum response of those was shown in the monitoring section (center of pile row section). Meanwhile, the torsion deformations are maximum as the 12 – 30 m ( ≈ 1.5Dtunnel - 4.5Dtunnel) away from the center of the pile row. For both short and long pile conditions, the influence zones of loaded pile row in a longitudinal direction are independent of the pile length and extended horizontal distance of 2Dtunnel away from the last pile within a row.
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    Item type:Publication,
    Comparative effects of adjacent loaded pile row on existing tunnel by 2d and 3d simulation models
    (2021-10-25)
    Heama, Narunat
    ;
    Jongpradist, Pornkasem
    ;
    ;
    Suwansawat, Suchatvee
    ;
    Jamsawang, Pitthaya
    Selecting suitable simulation methods for complex problems requires a careful balance between the predicted accuracy and computational effort. This research comparatively investigated the effects of adjacent loaded pile row on an existing tunnel in terms of tunnel deformation and lining force, displacement of soil surrounding between tunnel and pile and load transfer of the pile. Simulations were carried out by eight simulation models consisting of 3D finite element (FE) full models (model 1-2); 3D FE symmetry models (model 3-4); and a pile wall in 2D FE models (models 5-8). In loaded pile row simulation, simulations were performed with two pile types: volume pile and embedded pile. In 2D simulation, the 3D pile row was converted into 2D pile wall under plane strain condition by using three transformation methods. The results show that the predicted tunnel responses are adequately accurate as long as the reasonable soil movement behavior can be reproduced. The 2D equivalent dimensions and 2D equivalent axial rigidity are recommended since they provide conservative estimation on both tunnel deformation and lining forces. The 2D equivalent flexural rigidity is not recommended if the pile response is also of concern. The novelty of this research lies in the use and discussion on the applicability of various 2D and 3D models to simulate the effects of adjacent loaded pile row on the existing tunnel, as opposed to previous studies which focused on one or two simulation models.
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    Item type:Publication,
    Numerical modeling of single pile behaviors due to groundwater level rising
    (2021-07-01)
    Phoban, Harutus
    ;
    ;
    Behaviors of the pile foundation due to groundwater level rising were analyzed by a series two-dimensional finite element analyses with fully coupled flow-deformation analysis. The different numerical models of single bore pile depth and diameter in Bangkok subsoil were represented with the parametric study. The pile–soil movement due to groundwater levels rising between numerical simulation and a previous experiment of the centrifuge test as the same condition are in good agreement. With rising groundwater level, the reduction of pile capacity can be evidently performed by the increase of pile settlement relative to soil surface. Moreover, the development of the plastic point captured by the finite element analysis revealed the mechanism behind the reduction of pile capacity. In this study, the evaluation of pile stability due to groundwater level rising for preliminary guidelines to protect existing structures are proposed.
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    Item type:Publication,
    NUMERICAL INVESTIGATION ON PILE BEHAVIOR DUE TO THE RISING GROUNDWATER EFFECT
    (2021-01-01)
    Phoban, Harutus
    ;
    ;
    Since the late 1990s, the changing of groundwater level in the aquifer beneath Bangkok has been realized because the enforcement of groundwater laws and improvement of water supply have been adopted. Then, the groundwater with piezometric drawdown has risen to almost hydrostatic equilibrium. In the principle of soil mechanics, when the porewater pressure in soil mass increases, the effective stress decreases. This can affect underground structures. Under the soft ground condition such as Bangkok, Thailand, pile foundations are commonly constructed to support structures. With decreased effective stresses, the loss of ultimate load-carrying capacity of existing piles can occur, and the structures can be damaged. This research investigates the effects of the groundwater rising on the pile foundation in the Bangkok subsoil. An advanced numerical model with the fully coupled flow deformation analysis, both groundwater flow and soil deformation behaviors with time-dependent conditions are modeled, is conducted by using PLAXIS 2D. The results found that the calculation type of fully coupled flow deformation can express the pile-soil movement behavior. The pile-soil heave and the pile load capacity be significantly reduced during the groundwater rising event. Despite the reduction of pile load capacity with groundwater changed not enough to failure (Factor of safety <1.0), the pile stability should be concerned, and the optimum groundwater level must be controlled.
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    Item type:Publication,
    Improved prediction of pile bending moment and deflection due to adjacent braced excavation
    (2023-11-01)
    Phutthananon, Chana
    ;
    Jongpradist, Pornkasem
    ;
    Sirirak, Duangkamol
    ;
    ;
    Jamsawang, Pitthaya
    Deep excavations in dense urban areas have caused damage to nearby existing structures in numerous past construction cases. Proper assessment is crucial in the initial design stages. This study develops equations to predict the existing pile bending moment and deflection produced by adjacent braced excavations. Influential parameters (i.e., the excavation geometry, diaphragm wall thickness, pile geometry, strength and small-strain stiffness of the soil, and soft clay thickness) were considered and employed in the developed equations. It is practically unfeasible to obtain measurement data; hence, artificial data for the bending moment and deflection of existing piles were produced from well-calibrated numerical analyses of hypothetical cases, using the three-dimensional finite element method. The developed equations were established through a multiple linear regression analysis of the artificial data, using the transformation technique. In addition, the three-dimensional nature of the excavation work was characterized by considering the excavation corner effect, using the plane strain ratio parameter. The estimation results of the developed equations can provide satisfactory pile bending moment and deflection data and are more accurate than those found in previous studies.