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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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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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Natural Para Rubber in Road Embankment Stabilization
(2022-02-01)
Chaiyaput, Salisa
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Arwaedo, Nakib
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Jamsawang, Pitthaya
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Ayawanna, Jiratchaya
This is the first study on “ribbed smoked sheets (RSS)” as a geogrid reinforcement in geotechnical engineering. An RSS is a kind of natural para rubber. RSS (grade 3) was designed as a biaxial geogrid with an aperture size of 20 mm × 20 mm and a spacing of 20 mm. The RSS was found to be a significant functional layer when applied to the subbase lateritic soil layer. The lateritic soil with an RSS reinforcing layer was greatly improved regarding the California bearing ratio (CBR). Numerical simulation using two-dimensional finite element software was used to determine the optimal number and positions of the RSS reinforcing layers in road embankment stabilization. The simulation data in terms of horizontal displacement of unreinforced road embankments was validated by the collected data from the actual construction site. The RSS reinforced layer was varied from one to three layers under 61 analysis conditions. The highest safety factor was obtained with two layers of RSS at 0.1H below the top of the road embankment and 0.4H below the first RSS layer, suggesting a suitable installation of the RSS reinforcing layer. The RSS is thus strongly recommended as a reinforcing material in low CBR lateritic soil for the road embankment.
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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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