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Author: search.filters.author.Seeboonruang, UmaSubject: search.filters.subject.Numerical modeling

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    Numerical modeling of single pile behaviors due to groundwater level rising
    (2021-07-01)
    Phoban, Harutus
    ;
    Seeboonruang, Uma
    ;
    Lueprasert, Prateep
    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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    NUMERICAL INVESTIGATION ON PILE BEHAVIOR DUE TO THE RISING GROUNDWATER EFFECT
    (2021-01-01)
    Phoban, Harutus
    ;
    Seeboonruang, Uma
    ;
    Lueprasert, Prateep
    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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    Improving Groundwater Model in Regional Sedimentary Basin Using Hydraulic Gradients
    (2020-05-01)
    Tanachaichoksirikun, Pinit
    ;
    Seeboonruang, Uma
    ;
    Fogg, Graham E.
    Groundwater flow systems are strongly influenced by heterogeneity and anisotropy of hydraulic conductivity (K). Particularly in stratified clastic sedimentary aquifers, the vertical hydraulic gradient (dh/dz) is often very high, due to the low vertical hydraulic conductivity (K<inf>v</inf>) or high anisotropy (K<inf>h</inf>/K<inf>v</inf>). However, data on the vertical hydraulic gradient to calibrate the anisotropy is seldom available. We investigated the relationship between the variable K<inf>h</inf>/K<inf>v</inf> and the dh/dz computed by a groundwater flow model to improve the regional parameterization using an extensive data base on 3D distribution of hydraulic head. Although it is commonly assumed that the value of K<inf>h</inf>/K<inf>v</inf> is 10, our values typically ranged between 10 and 10<sup>5</sup>, because the maximum K<inf>h</inf>/K<inf>v</inf> was 10<sup>5</sup> in this regional basin. The simulations used MODFLOW-2000. We found that the high K<inf>h</inf>/K<inf>v</inf> contributed to high dh/dz, while identifying locations of potentially good vertical connectivity between the aquifer zones, where dh/dz is very low and difficult to measure sufficiently accurately. Sensitivity analysis of dh/dz to recharge and pumping from wells showed that recharge led to change in inflow of groundwater that led to head change, which in turn led to change in dh/dz. While, pumping contributed to aquifer outflow, as change in head drawdown around the influence zone, in turn changed dh/dz. Additionally, dh/dz in a shallower aquifer was more strongly affected by recharge and pumping.