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    Vibro-compaction at a land reclamation site in Phuket, Thailand
    (2021-08-01)
    Chaiyaput, Salisa
    ;
    Bergado, Dennes T.
    ;
    Kovittayanun, Nuttaphong
    Phuket is the biggest island province in Thailand. Located in the southern part of the country, this island is famous and a favourite destination for foreign and Thai tourists alike. Consequently, this province continually develops with booming tourism and hence there is a need for large and advanced infrastructure. Construction projects are increasing each year, but the available land area is limited and land reclamation has therefore become an alternative. Sand backfill material is available on the island. However, the loose sand fill needs to be densified for structural support or structural foundations, and the ground improvement technique called vibroflotation is suitable for improving the sand density in a small area over a short period. This paper presents an assessment of the effectiveness of vibroflotation in the densification of sand fill, which was applied for the first time in Thailand. The standard penetration test values of the sand fill before and after improvement were compared, evaluated and confirmed with regard to liquefaction susceptibility during earthquake occurrences. It was confirmed that the vibroflotation technique can increase the density of sand fill in land reclamation and can increase its bearing capacity as well as prevent liquefaction during earthquakes.
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    A simple solution for prefabricated vertical drain with surcharge preloading combined with vacuum consolidation
    (2021-02-01)
    Nguyen, Trong Nghia
    ;
    Bergado, Dennes T.
    ;
    Kikumoto, Mamoru
    ;
    Dang, Phuoc H.
    ;
    Chaiyaput, Salisa
    Prefabricated vertical drains (PVDs) with the surcharge preloading and vacuum consolidation has become considerably popular for ground improvement projects. A simple solution that incorporates the fundamental embankment features, such as the average degree of consolidation and excess pore pressure, are essential for the design of soft ground improvements by PVDs with vacuum preloading. However, most of the solutions for vertical drains with vacuum consolidation require numerical simulations, whose implementation tends to be laborious. In contrast, a simple solution for vacuum consolidation under time-dependent loading has not yet been proposed. In this study, a simple solution that can be easily incorporated into a conventional spreadsheet is derived for PVDs with vacuum preloading by applying the Laplace transform technique. The proposed solution accounts for several actual construction conditions, such as initial surcharge load, vacuum pump trial period, variations of radial permeability, and time-dependent loading. The results obtained from this proposed approach were validated with those from the finite element method and field data from the case study of the Cai Mep International Terminal project in southern Vietnam. The derived solutions, including the excess pore pressures and average degrees of consolidation, were in good agreement with the predicted and observed data.
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    Microstructures within and outside the smear zones for soft clay improvement using PVD only, Vacuum-PVD, Thermo-PVD and Thermo-Vacuum-PVD
    (2020-12-01)
    Bergado, Dennes T.
    ;
    Chaiyaput, Salisa
    ;
    Artidteang, Suthasinee
    ;
    Nguyen, Trong Nghia
    Previous investigators have found increasing rates odf consolidation with increasing degrees of soft clay improvement using PVD only, Vacuum-PVD, Thermo-PVD and Thermo-Vacuum-PVD). This paper utilized scanning electron microscope (SEM) to evaluate and compare the microstructures of the clay specimens obtained from within the smear zone of both undisturbed and reconstituted samples in small consolidometer as well from within and outside the smear zone of reconstituted samples in large consolidometer. Before improvement, both reconstituted and undisturbed specimens showed anisotropic microstructures. In reconstituted specimen, face to face preferred orientations are revealed parallel to the horizontal plane. Meanwhile, in the undisturbed specimen, some degree of random edge to face mixed with face to face orientations were displayed. After improvement, the microstructures of Thermo-Vacuum-PVD revealed high levels of edge to face orientation in the vertically dominated smear zone, followed by Thermo-PVD, Vacuum-PVD, and PVD only. Moreover, the microstructures of specimens in the horizontally dominated outside of smear zone exhibited mainly face to face orientation and progressively mixed with edge to face orientation. The increasing intensities of edge to face microstructures were successfully correlated with increasing flow parameters and measured shear strengths corresponding to the increasing levels of improvement.
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    Successful mitigations of riverbank slope stabilizations and road failures caused by excessive rainfalls due to climate change at national road 1B (NR 1B) in Laos PDR
    (2020-01-01)
    Bergado, Dennes T.
    ;
    Chaiyaput, S.
    The sites of the successful road embankment and pavement repairs were located in Laos PDR at National Road 1B (NR 1B). National Road (NR) 1B connects Laos to China. Illustrations of the road embankment and pavement failures and their successful mitigations are discussed. The mitigations of the first case (Case 1) consist of PEC-150 geotextile reinforcements with gabions and wrapped around soil bag facing combined with intercepting trench drains wrapped around with TS-50 geotextiles. In the second case (Case 2), the proposed pavement repairs consisted of intercepting trench drains wrapped around with TS-50 geotextiles combined with PEC-150 geotextile reinforcements of the gravel sub-base replacing the upper portions of the embankments underlying the pavements. The intercepted subsurface seepage lowered the water table and collected and safely directed the seepage flow to drainage pipes and channels.