||A. Alowaisy, N. Yasufuku, Influence of Layer Thickness on Evaporation and Water Redistribution in Layered Soil Profiles, Desert Technology Desert Technology 12th (DT 12) International Conference, 2015.11.
||Adel ALOWAISY, Noriyuki YASUFUKU, Optimizing Adaptations and Experimental Evaluation of the Actual Evaporation and Water Redistribution Through Double Layered Soil Profiles, The 8th Asian Joint Symposium on Geotechnical and Geoenvironmental Engineering (JS-Tainan 2016), 37-42, 2016.11.
||April 2018 slope failure and future problems in Yabakei, Oita, Japan.
||A. Alowaisy, N. Yasufuku, R. Ishikura, Hatakeyama M, Rapid direct measurement of the soil water characteristics curve and hydraulic conductivity function utilizing the continuous pressurization method under the drying phase, IS-Atlanta 2018 (Geo-Mechanics from Micro to Macro), 2018.09.
||A. Alowaisy, N. Yasufuku, Characteristics of the second stage of evaporation and water redistribution through double layered sandy soil profiles, The Lowland Technology International Journal, 20, 3, 273-284, 2018.12, Evaporation from porous media involves a complex pore scale water and vapor transportation that directly affects the liquid phase distribution and fluxes. The presence of textural contrast boundary in multilayered profiles adds to the complexity. This study aims at evaluating the textural contrast boundary depth and individual layer thickness influence on the actual evaporation and water storage through double-layered soil profiles. For coarse overlying fine sand, it was found that the top layer small capillaries contribute to the majority of water lost through the falling rate stage. Considering fine overlying coarse sand profiles, the pumping phenomenon from the bottom coarse layer to the top fine layer occurs before the arrival of the drying front to the textural boundary due to the increasing suction forces within the top fine layer. The water storage capability of double layered soil profiles depends highly on the top to the bottom small capillaries ratio multiplied by the layer thickness ratio. Regardless the atmospheric conditions and layering sequence, it was concluded that the shallower the textural contrast boundary results in decreasing the total duration required to achieve the residual evaporation stage thus leads to higher water storage capabilities through the first and second evaporation stages..
||Sakata, T., Yasufuku, N., Ishikura, R., Alowaisy, A., Mechanical and hydrological time-dependent properties of granulated blast furnace slag-sand mixture in soft ground improvement, The Lowland Technology International Journal, 20, 3, 285-296, 2018.12, 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..
||Okri Asfino Putra, Noriyuki Yasufuku, Ryohei Ishikura, Adel Alowaisy, Yuko Kawaguchi, Mechanical behaviour of unsaturated undisturbed black volcanic ash soil under static and cyclic loading, E3S Web of Conferences, 10.1051/e3sconf/20199207004, 92, p. 07004, 2019.06, © The Authors, published by EDP Sciences. The mechanical behaviour of unsaturated undisturbed black volcanic ash soils was investigated using a constant volume direct shear apparatus. A series of static and cyclic tests were conducted under unsaturated and saturated samples. The cyclic test under two patterns were adopted. First type of pattern, cyclic one-sided shearing was applied. For the second type, two-sided shearing was conducted. For further understanding of the chemical content and microstructure, X-Ray Fluorescence analysis (XRF) and Scanning Electron Microscope (SEM) were evaluated. It was found that, under static shearing, the unsaturated sample exhibits a higher apparent cohesion and friction angle in comparison to the saturated sample. The normalized vertical stress under one-sided cyclic shearing in both overconsolidated and normally consolidated samples rapidly reduced at the beginning of shearing. This might be attributed to increase of the pore water pressure during shearing. Furthermore, there is a significant difference between the normalized shear stress under cyclic one-sided and two-sided shearing. For the two-sided cyclic shearing test, the normalized shear stress value is higher than the one-sided cyclic shearing test. In addition, the normalized shear stress under unsaturated condition is significantly larger. This can be related to the suction forces to the total strength of soils. The main chemical content of the black volcanic ash soil is allophane. Further, the microstructure of the black volcanic ash changes due to shearing. For the overconsolidated sample, particles of soil more severe damage than normally consolidated sample..
||Adel Alowaisy, Noriyuki Yasufuku, Ryohei Ishikura, Masanori Hatakeyama, Shuu Kyono, Novel rapid measurement system of undisturbed soils water characteristics curve utilizing the continuous pressurization method, E3S Web of Conferences, 10.1051/e3sconf/20199207008, 92, p. 07008
, 2019.06, © The Authors, published by EDP Sciences. Through this paper, a sampling methodology and a novel full automatic system adopting the continuous pressurization method which is capable of determining the Soil Water Characteristics Curve (SWCC) for both remoulded and undisturbed samples in a very short time were developed. The proposed system was validated by comparing the SWCCs of standard testing soils obtained using the developed system to the SWCCs obtained using a conventional method. Remoulded and undisturbed natural soil samples were tested, where the degree of disturbance influence on the obtained SWCC was discussed. In addition, the undisturbed samples containing moulds material influence on the obtained SWCC was investigated. It was found that remoulded samples do not properly represent the in-situ conditions with significant error that should be carefully considered when conducting analysis and proposing countermeasures against unsaturated soils related Geo-disasters. In addition, the material which the containing mould is made from has minor influence on the obtained SWCC which can be neglected. Finally, it can be concluded that the developed undisturbed soil water characteristics curve obtaining system is direct, rapid, reliable and simple. In addition, the proposed undisturbed sampling and testing methodology can be used to accurately evaluate the spatial variations of the SWCC regardless the heterogeneity of the soil profile..
||Hatakeyama, M., Kyono, S., Yasufuku, N., Ishikura, R., Alowaisy, A.M.
, Pore water pressure profile development through soil water characteristics curve determination utilizing the continuous pressurization method, Japanese Geotechnical Society Special Publication, Proceedings of 7th Asia-Pacific Conference on Unsaturated Soils
, 7, 2, 272-280, 2019.08.
||Alowaisy, A.M., Yasufuku, N., Ishikura, R., Hatakeyama, M., Kyono, S.
, Rapid concurrent measurement of the soil water characteristics curve and the hydraulic conductivity function utilizing the continuous pressurization method, Japanese Geotechnical Society Special Publication, Proceedings of 7th Asia-Pacific Conference on Unsaturated Soils, 7, 2, 366-375, 2019.08.
||Necessity of Measuring the Pore Water Pressure when Determining the SWCC.
||Soil Water Characteristics Curves of In-situ Samples with Low Disturbance Obtained from Disaster Slopes.
||Alowaisy, A, Yasufuku, N, Ishikura, R & Hatakeyama M.
, Validation of the direct measurement of the soil water characteristics curve using the newly developed continuous pressurization method, Proceedings of the 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering (16ARC)
||P. Okri, N. Yasufuku, R. Ishikura, A. Alowaisy, Development of new suction controlled direct shear box apparatus for unsaturated soil., Technical Forum on Mitigation of Geo-disasters in Asia, P026, 114-119, 2019.11.
||A. Alowaisy, N. Yasufuku, R. Ishikura, M. Hatakeyama, S. Kyono, Discrepancies associated with adopting remolded samples when determining the retention characteristics of natural soil profiles., Technical Forum on Mitigation of Geo-disasters in Asia, P016, 64-69, 2019.11.
||S. Nagata, R. Ishikura, N. Yasufuku, A. Alowaisy, Evaluation of crushed Granulated Blast Furnace Slag – sand mixtures liquefaction characteristics under unified compaction energy, Technical Forum on Mitigation of Geo-disasters in Asia, P019, 80-83, 2019.11.
||Okri Asfino Putra, Noriyuki Yasufuku, Ryohei Ishikura, Ahmad Rifa'i, Adel Alowaisy, Yuko Kawaguchi, Effect of soil structure disturbance on the shear strength of black volcanic ash soil, E3S Web of Conferences, 10.1051/e3sconf/202015602004, 156, p. 02004
, 2020.03, © 2020 The Authors, published by EDP Sciences. The effect of soil disturbance on the shear strength of black volcanic ash soil was investigated using a constant volume direct shear apparatus. Disturbance of soil structure was considered as the pore size distribution which obtained from the soil-water characteristic curve (SWCC). The disturbed sample was used as a representation of soil structure disturbance due to earthquake shakes. A series of cyclic tests were conducted under unsaturated and saturated samples. It was found that the undisturbed samples exhibit a unimodal pore structure, and the disturbed samples indicate to a bimodal pore structure. Since the pore structure of the disturbed sample is unstable, the degradation index value is higher than that of the undisturbed sample and increases with the increasing number of cycles. In other words, the cyclic normalized vertical stress of disturbed samples degrades faster. Furthermore, the degradation index value in the normallyconsolidated samples was found to be larger than the overconsolidated. It might be attributed to increasing of the pore water pressure during shearing. Where in the over-consolidated samples is lower than normally-consolidated. On the other hand, the normalized shear stress of unsaturated samples, it is slightly larger due to the suction forces in the total strength of soils..
||Adel Alowaisy, Noriyuki Yasufuku, Ryohei Ishikura, Masanori Hatakeyama, Shuu Kyono, Continuous pressurization method for a rapid determination of the soil water characteristics curve for remolded and undisturbed cohesionless soils, Soils and Foundations, 10.1016/j.sandf.2020.03.014, 60, 3, 634-647, 2020.06, © 2020 Natural disasters like earthquakes and heavy rainfall events induce slope failures and other disasters. Proper determination of the water retention properties of porous mediums is necessary. The conventional Soil Water Characteristics Curve (SWCC) determination techniques are limited due to their complexity and lengthy time required. A highly accurate simple remolded and undisturbed samples SWCC determination method that requires a short time is lacking. A novel automatic system which adopts the continuous pressurization method and allows the direct determination of the SWCC in a short time suitable for use with remolded and undisturbed samples was developed. The accuracy of the newly developed system was validated, and it was shown to have excellent repeatability. It is a reliable and direct method that requires a short time for the SWCC determination, with the drying and wetting SWCCs obtainable in less than 10% of the time required using the conventional multi-step flow method. Consideration of the pore water pressure was shown to be necessary when calculating the matric suction utilizing the axis-translation technique. Finally, because remolded samples do not properly represent the in-situ natural conditions, the significant discrepancies should be carefully considered when conducting analysis and proposing countermeasures against unsaturated soil-related Geo-disasters..
||Measurements of Unsaturated Hydraulic Characteristics for Sandy Soil utilizing the Continuous Pressurization Method.
||Okri Asfino Putra, Noriyuki Yasufuku, Adel Alowaisy, Ryohei Ishikura, Ahmad Rifa'i, Yuko Kawaguchi, Shear strength characteristic of unsaturated undisturbed black volcanic ash soil in Kumamoto under static and cyclic loading, The Lowland Technology International Journal, 22, 2, 279-289, 2020.09, Black volcanic ash soil which is also known as Kuro-boku soil in Japan is a problematic type of soil. Kuro-boku is usually rich with allophane minerals, which are characterized by unique problematic properties. Through this paper, the shear strength and characteristics of the black volcanic ash soil collected at Kumamoto slope failure after earthquake 2016 were studied using three main approaches. The chemical composition of the black volcanic ash soil was investigated using the X-ray fluorescence analysis. Furthermore, the soil structure disturbance effect due to the earthquake shakes on the total shear strength was evaluated using a simple method that considers the pore size distribution that is reflected from the soil-water characteristic curve. In addition, the constant volume direct shear box considering static and cyclic tests were carried out. It was found that the main chemical content of the black volcanic ash soil is allophane which accounts for about 94%. Furthermore, the undisturbed samples exhibit a unimodal pore structure, and the disturbed showed a bimodal pore. Since the pore structure of the disturbed sample is unstable, the static shear strength tends to be lower and the degradation index value is higher than that of the undisturbed sample..
||Noriyuki Yasufuku, Adel Alowiasy, Lessons from Geo-Disasters Caused by Heavy Rainfall in Recent Years in Kyushu Island, Japan, Understanding and Reducing Landslide Disaster Risk, In Workshop on World Landslide Forum, Springer, Cham., 10.1007/978-3-030-60713-5_14, 141-147, 2020.11.
||Evaluation of the Soil Water Characteristics Curve using the Continuous Pressurization Method Linked with the Practical Measurement of the Soil Shear Strength.
||Evaluation of the hydrological characteristics of the damaged river embankment and its application
||A.Jugdernamjil, N. Yasufuku, A. Alowaisy, Prediction of ultimate lateral capacity of rigid spiral pile under static loading in cohesionless soil, The Lowland Technology International Journal, 23, 2, 17-25, 2021.12, 1g model test is carried out to evaluate the ultimate lateral capacity of the spiral model pile in dense and medium dense cohesionless soil. The spiral model pile is scaled down using a proper similarity equation considering the equivalent second moment of area. The equivalent second moment of the area was obtained from a four-point bending test on a flat bar and compared with a spiral bar. In order to identify the lateral capacity of the spiral model pile, the conventional pipe and flat bar model piles were conducted as well. Winkler's model was adopted to predict the rigid spiral pile's ultimate lateral capacity in cohesionless soil. A simplified model is proposed by developing ultimate lateral soil pressure. The novel shape factor for spiral was obtained for the evaluation of ultimate lateral soil pressure by considering the projected area of the pile. The projected area of the spiral pile was compared with the pipe pile. The comparison study was conducted to spiral, flat, bar, and pipe pile, respectively, for inspecting accuracy. Among the comparison, the proposed model was indicated as a more accurate model than others. The spiral pile was shown a similar performance with a flat bar in both the empirical and the experimental results..
||A.Putera, N.Yasufuku, A.Alowaisy, A.Rifai, Optimizing modified triaxial testing for small strain zone using local displacement transducers and bender element for cement-treated soft soil, Proc. of the International Conference on Disaster Mitigation and Management (ICDMM 2021), 331, 03003, 2021.12.
||Jumana Hussary, Adel Alowaisy, Noriyuki Yasufuku, Ryohei Ishikura, MontherAbdelhadi, Pore structure and falling rate stage of evaporation in homogeneous sandy soil profiles, Soils and Foundations, https://doi.org/10.1016/j.sandf.2022.101108, 62, 2, 101108, 2022.04, Recently, climate change has been causing severe droughts and water scarcity in drylands. A proper understanding of the soil surface-atmosphere boundary fluxes is essential to combatting such environmental problems. In those regions, evaporation is considered to be the dominant flux. It is divided into three stages that follow different mechanisms and are highly dependent on the soil properties. Most of the existing studies focus on the evaporation process from a macroscale perspective and estimate the evaporation rate based on the atmospheric conditions, while only a few of them consider the soil properties. This paper studied the influence of the soil pore structure on the actual evaporation and formation of the unsaturated layer. Homogeneous drying sandy soil column tests were conducted under a unified low atmospheric demand. The pore structure was investigated by varying the texture and relative density. The significance of Stage 2 in the evaporation process was asserted. Additionally, it was affirmed that vapor diffusion is dominant during Stage 2, where the actual evaporation reduction rate depends on the receding rate of the vaporization plane. Finally, a comprehensive, robust, and easily determined index, that correlates well with the duration and evaporated water during Stage 1 and Stage 2, was proposed. The Pore Size Distribution Index (IPSD) was found to reflect the variations in the pore structure and to consider the capillary and diffusion flow mechanisms. It serves as a fundamental step towards evaluating the actual evaporation and drying front depth during the evaporation process..