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R. Ishikura
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Civil Engineering, Building, Construction & Architecture Engineering Transportation

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Evaluation of settlement behavior of the improved ground by using floating type columns during consolidation Z. B. Jiang; R. Ishikura; N. Yasufuku
Lowland Technology International Vol 17 No 2, Sep (2015)
Publisher : International Association of Lowland Technology

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Abstract

For soft soil engineering, in many cases, the foundation directly on natural ground cannot satisfy the requirement, such as embankment on deep soft clay layer. Consequently, a technology of combining the float-type cement-treated columns and surface stabilization is developed for reducing the settlement and the construction cost. In order to apply this technology for practice, it is important to predict the total settlement of the ground in relation to the important factors. In this paper, in order to evaluate the consolidation settlement behavior, a time-dependent skin friction model for the columnsoil interaction is developed to describe the nonlinear relationship between column shaft shear stresses and effective vertical pressure in the surrounding soft clay. The timedependent equivalent skin friction length which treating a part of floating type improved ground with a length of αH1 as an unimproved portion can be obtained based on a homogenization theoretical method. The compression settlement of this unimproved portion can be computed using the properties of soft clay alone. For verifying the effectiveness of this method, a set of laboratory model tests were performed. Furthermore, the settlement behavior and stress distribution characteristics were investigated by image analysis.
Effects of sugarcane bagasse ash (SCBA) on the strength and compressibility of cement stabilized peat M. K. Abu Talib; N. Yasufuku; R. Ishikura
Lowland Technology International Vol 17 No 2, Sep (2015)
Publisher : International Association of Lowland Technology

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This research objective is to evaluate effectiveness of sugarcane bagasse ash (SCBA) inclusion in peat stabilization. To develop the optimal mix design, stabilized peat specimens were tested in unconfined compression. Energy Dispersive Xray (EDX) and Scanning Electron Microscope (SEM) apparatus was used to examine elemental composition and microstructure. Consolidation tests were carried out in a standard Oedometer apparatus on the obtained optimum peat-cement-bagasse (PCB) mixture. It was found that stabilized peat comprising 20% partial replacement of OPC with SCBA has the maximum UCS and discovered to be about 1.2 times greater than UCS of peatcement (PC) specimen. The UCS of optimum PCB mixture specimens increased with curing duration in water. Compared to untreated soil, SEM results for stabilized peat gave the significant pore improvement. EDX results prove that lower carbon (C) and higher calcium (Ca) fractions shows the better results of strength. There was a significant reduction of void ratio (e) for optimum PCB mixtures as compared to untreated peat. It was observed that preconsolidation pressure, σ’c were increase with curing period. Results finding shows that the stabilized peat Cα/Cc ratios were decline dramatically from untreated peat which is indicating the stabilized mixture can effectively reduce the secondary compression.
Evaluation of rainfall erosivity and impact forces using strain gauges K. Vilayvong; N. Yasufuku; R. Ishikura
Lowland Technology International Vol 17 No 4, March (2016)
Publisher : International Association of Lowland Technology

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Rainfall erosivity and impact forces are key meteorological parameters for predicting rainfall-induced hazards and disasters. Erosivity of rainfall is widely indicated by its kinetic energy or momentum that is widely derived from drop diameters or drop size distribution and velocity of raindrops. Raindrop velocity and impact forces describe the rainfall erosivity dissipated to impacting surface. These parameters are not commonly evaluated and available in practice due to cost and capability of measuring instruments. A strain gauge-based device was developed for automatic and continuous measurement of the parameters in laboratory. The strain sensor, with the aid of a portable, dynamic, and high frequency data acquisition, was calibrated to capture the falling velocity of a 4.00 mm diameter waterdrop with varying heights. Results of the falling velocities of a waterdrop against heights in this study showed a close agreement with results from literature data and equations for the falling velocity and its impact force of a waterdrop were derived. In addition, results of using the equations to derive terminal velocities and impact forces as a function of drop diameters were presented.
Mechanical and hydrological time-dependent properties of granulated blast furnace slag-sand mixture in soft ground improvement T. Sakata; N. Yasufuku; R. Ishikura; A. Alowaisy
Lowland Technology International Vol 20 No 3, Dec (2018)
Publisher : International Association of Lowland Technology

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Every year about 20 million tons of Granulated Blast Furnace Slag (GBFS) are produced as a manufacturing byproduct. GBFS is mainly utilized in cement production accounting for 70% of the total utilized weight, while the geotechnical engineering applications accounts for 2%. Therefore, finding innovative utilization methods is a necessity. It was reported that the GBFS can be used as substitutive material in sand compaction pile (SCP) method. This study aims at evaluating the time-dependent mechanical, hydrological and chemical properties of the GBFS and the GBFS-sand mixtures. It was found that for early hydration stage, the hydrological and mechanical properties of the GBFS depends on the microstructure of the material, while the generation of the calcium silicate hydrate can be neglected. On the other hand, for longer curing time the influence of the calcium hydrate silicate generation becomes significant. Finally, it was concluded that mixing the GBFS with sand is a simple efficient way to control the time dependent mechanical, hydrological and chemical properties of the GBFS, however, the combined effect of the hydration reaction rate and the void ratio developments in response to the mixing ratio and the curing time should be properly considered to optimize utilizing the GBFS.
Correlation Between Shear Wave Velocity and Liquefaction Resistance For Sandy Soils With A Shearing History Using Cyclic Tri-Axial Tests G. J. Liu; N. Yasufuku; R. Ishikura
Lowland Technology International Vol 21 No 2, Sep (2019)
Publisher : International Association of Lowland Technology

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Abstrac
Prediction of Uplift Capacity of Belled-type Pile with Shallow Foundation in Sandy Ground J-G. Kang; N. Yasufuku; R. Ishikura; A. Y. Purnama
Lowland Technology International Vol 21 No 2, Sep (2019)
Publisher : International Association of Lowland Technology

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This paper describes a semi-empirical model for predicting the uplift resistance of a belled-type pile considering the relative density of the ground. The variable parameters were utilized in the model are the pile length, the diameter of pile tip, the diameter of pile, and the angle of internal friction in the ground. Moreover, the inclination angle of pile tip and the relative density of the ground, which are not studied in the previous researches, were considered. In this study, an experimental model was conducted with various conditions such as the relative density of the ground and the inclination angle of pile tip those are designated to determine the failure surface of the ground. Based on results, a new model which can be applied to the belled-type pile was proposed by improving the limit equilibrium equation in the previous models. In addition, to confirm the reliability of the newly proposed a model of limit equilibrium equation of the belled-type pile, the models which are presented in the previous studies were compared with the proposed model. Consequently, the proposed model in this study correspond the higher reliability in comparison with the previous models.
Co-Authors A. Alowaisy A. Y. Purnama G. J. Liu J-G. Kang K. Vilayvong M. K. Abu Talib N. Yasufuku T. Sakata Z. B. Jiang