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Improved prediction of pile bending moment and deflection due to adjacent braced excavation
(2023-11-01)
Phutthananon, Chana
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Jongpradist, Pornkasem
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Sirirak, Duangkamol
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Lueprasert, Prateep
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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.
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Application of a cement–clay–air foam mixture as a lightweight embankment material for construction on soft clay
(2023-07-01)
Chaiyaput, Salisa
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Ayawanna, Jiratchaya
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Jongpradist, Pornkasem
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Poorahong, Hatairat
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Sukkarak, Raksiri
Lightweight air foam materials can be used in pavement structures, for example, as embankments and subbase and base layers. Soft clay can be mixed with cement and air foam to generate a lightweight material. However, most previous studies have presented only laboratory test results for these materials and have not shown real-world applicability. The current study aims to demonstrate the application of a cement–clay–air foam mixture as a lightweight embankment material to reduce the settlement of soft Bangkok clay foundations induced by embankment weight. An experimental investigation to determine unconfined compressive strength (q<inf>u</inf>) was initially conducted in the laboratory to establish the ideal quantities of soft clay, air foam, and ordinary Portland cement required for embankment construction using the clay mixture. A full-scale lightweight embankment of area 14 m × 14 m and height 2.5 m was constructed on an 11 m thick soft clay layer to observe embankment settlement behavior on the soft clay foundation. The q<inf>u</inf> values of the lightweight materials obtained from the site were 1.3–1.8 times higher than those in laboratory tests. The mixtures with wet field unit weights of 0.6, 0.8, and 1.0 kN/m<sup>3</sup> exhibited q<inf>u</inf> values of 430–620 and 770–1000 kPa, respectively, higher than the standard requirements (> 100 kPa for 7 curing days and > 200 kPa for 28 curing days). Based on monitored data, the lightweight embankment reduced settlement by as much as 80 % compared with a traditional embankment. Therefore, lightweight clay materials are recommended for use in the construction of road embankments on soft clay.
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Structural Responses of a Tunnel Lining Due to an Adjacent Loaded Pile
(2023-06-01)
Lueprasert, Prateep
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Jongpradist, Pornkasem
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Jongpradist, Pattaramon
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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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Destructive and nondestructive characteristics of solidified reservoir sediments incorporating microstructural analyses
(2022-08-01)
Jamsawang, Pitthaya
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Poorahong, Hatairat
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Jongpradist, Pornkasem
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Likitlersuang, Suched
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Chaiyaput, Salisa
Reservoir sediments create a range of severe problems for hydropower dams. Although reservoir sediments can be excavated, nonetheless, sizeable dumping lands for such excavated sediments are unavailable at this time. This paper presents an experimental investigation of the destructive and nondestructive properties and microstructural characteristics of reservoir sediments solidified with fly ash–cement blend for reuse as construction materials. The obtained natural sediment was classified as well-graded sand with silt. The destructive experiments comprised unconfined compression, indirect tension, California bearing ratio, resilient modulus, and durability against wet–dry cycle tests, while the nondestructive experiments included a free–free resonance test. Microstructural investigations consisting of X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and energy-dispersive X-ray spectrometry were performed to verify the macroscale test results. The results showed that fly ash–cement blend exhibited increased strength values on the order of 2 to 9 times that of unsolidified sediments. Using fly ash-blended cement was more effective than using sole cement or sole fly ash, and mixtures with 10% fly ash delivered the best strength and modulus values. Various functional empirical correlations were proposed. Utilizing six wet–dry cycles is acceptable because the strength of the samples subjected to the six wet–dry cycles was lower than the given value. The results of the peak intensities of calcium silicate hydrate, mass losses, calcium contents, and scanning electron microscopy images derived from the microstructural investigations confirmed the macroscale test results.
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Comparative effects of adjacent loaded pile row on existing tunnel by 2d and 3d simulation models
(2021-10-25)
Heama, Narunat
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Jongpradist, Pornkasem
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Lueprasert, Prateep
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Suwansawat, Suchatvee
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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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Dependence Of Tunnel Deformation Due To Adjacent Pile Under Loading On Tunnel Geometry
(2019-01-01)
Lueprasert, Prateep
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Jongpradist, Pornkasem
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Ruangvirrojanakul, Kodchamon
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Suwansawat, Suchatvee
With rapid urbanization, large number of tunnels with various dimensions have been constructed for transportation and utility systems in many big cities. At the same time, the constructions of infrastructures using a pile foundation system are also necessary in urban area. With limited space, the existing tunnels can be inevitably impacted by the newly constructed pile-supported structures. With various design criteria of tunnel lining, the size and thickness are varied from project to project. With an adjacent pile under loading, different degrees of impact on these tunnels are expected. This study numerically investigates the effect of tunnel diameter and lining thickness on tunnel deformation due to adjacent pile under loading. The MRTA and WMA tunnels in Bangkok subsoil are chosen as the reference cases for investigation. From a series of parametric study, a relationship between the tunnel deformation and dimensionless parameter, which include the size and thickness of lining, can be successfully established.
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Investigation on pile-soil-tunnel interaction due to adjacent loaded pile row by 3D FEM
(2018-08-14)
Heama, Narunat
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Jongpradist, Pornkasem
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Lueprasert, Prateep
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Suwansawat, Suchatvee
The effect of adjacent loaded pile row on the existing tunnel is analysed by 3D finite element method. The MRTA project is used as reference case in this study. The case study is divided into two cases, tunnel and pile tip located in soft clay and stiff clay, respectively. The pile diameter of 1 m and pile tip located at the elevation of tunnel crown with various number of piles within the row were considered. The analysis results are shown in terms of total soil displacement (without tunnel) and maximum tunnel deformations. Both total soil displacements and tunnel deformation increase with the number of piles and approach a maximum value when the number of piles is greater than 13 and 11 for cases tunnel in soft and stiff clay, respectively. This reveals that the tunnel deformation mechanism is primarily due to the soil displacement.
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Numerical investigation of tunnel deformation due to adjacent loaded pile and pile-soil-tunnel interaction
(2017-11-01)
Lueprasert, Prateep
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Jongpradist, Pornkasem
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Jongpradist, Pattaramon
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Suwansawat, Suchatvee
An adjacent construction with a pile foundation in dense urban areas can contribute to possible damage to or an operational safety concern for existing tunnels. To establish a preventive measure in the design stage, a proper assessment method for the impacts of an adjacent pile under loading on a tunnel and an understanding of pile-soil-tunnel interaction are essential. This article recommends an assessment method for tunnel deformation, defined by the maximum extension and maximum contraction of the tunnel diameter and their associated axes with respect to the horizontal and vertical directions, respectively. The method could appropriately trace the changes to the tunnel diameter and the global distortion of the tunnel lining. Using a series of three-dimensional elasto-plastic numerical analyses conducted to investigate the influences of an adjacent loaded pile on an existing tunnel for varying pile tip positions with respect to the tunnel and soil stratum, the proposed method can effectively capture the response of the deformed tunnel as a distorted ellipse shape. Investigation of the analysis results from this assessment method in conjunction with those of the supplementary analyses of pile load reasonably reveal the pile-soil-tunnel interaction mechanism behind the tunnel deformation behaviour due to an adjacent loaded pile.
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Investigation on tunnel responses due to adjacent loaded pile by 3D finite element analysis
(2017-01-01)
Heama, Narunat
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Jongpradist, Pornkasem
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Lueprasert, Prateep
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Suwansawat, Suchatvee
Underground structures are popularly utilized in urban development, especially tunnels for both transportation and utilities. The interaction problem between existing tunnel and piles from new constructed structures thus becomes unavoidable in dense population area. The tunnel loses its stability if the additional forces and changed diameters (due to adjacent piles under loading) of tunnel lining are drastically high. This depends on many factors, such as the clearance and pile tip level with respect to tunnel position. For preliminary assessment during the first stage of design, it is necessary to estimate this impact. The concept of tunnel protection zone is commonly adopted. However, to establish the tunnel protection zone for adjacent loaded pile, the understanding on this interaction problem is essential. This study analyzes the effect of adjacent pile under loading on the existing tunnel by 3D finite element method. The case study is the tunnel of MRTA project subjected to an adjacent 1 m bored pile under loading with various lengths and clearances. The additional forces (bending moment and axial force) and the tunnel deformations are investigated. The results show that the additional forces and the tunnel deformations decrease when the clearance increase and become insignificantly increasing when the clearance is larger than 3.5 m. The distribution patterns of additional forces and tunnel deformation are similar.
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Three dimensional finite element analysis for preliminary establishment of tunnel influence zone subject to pile loading
(2015-06-28)
Lueprasert, Prateep
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Jongpradist, Pornkasem
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Charoenpak, Kitcha
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Chaipanna, Pattanasak
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Suwansawat, Suchatvee
Urban development often involves the construction of infrastructures that require deep foundations or piles. Due to the existence of tunnels, the need to construct deep foundations in close proximity contributes to possible damage to the tunnels and operational safety concern. The concept of influence zones has been proposed as restrictive guidelines for construction adjacent to underground tunnels. However, the current influence zones are based on the conventional assumption of soil failure due to tunnelling rather than on an understanding of the pile-tunnel interaction. This paper thus analyses the impacts of piles under loading on the subway tunnel of the Mass Rapid Transit Authority of Thailand in Bangkok using the 3D finite element method. The analyses are carried out to investigate factors in tunnel deformations. The results show that the significant factors are the relative position of the pile tip with respect to the tunnel position as well as the soil type where the tunnel is located. In addition, this paper tentatively proposes a new influence zone for pile construction adjacent to the existing tunnel.

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