Articles

  1. POTENTIAL FOR SILICA-BASED SOLIDIFICATION MATERIALS AS SOIL IMPROVING AGENTS Download Article

    Shinya Inazumi, Takashi Shinsaka, Ryo Hashimoto and Yoshihiro Nakagishi
    • Article Type: Research Article
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    • Pages (1-4)
    • No of Download = 598

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    In a series of studies, the authors have developed a powdery silica-based solidification material composed of heat-treated inorganic solid wastes with a high content of silica products (such as waste glass and waste fly ash) mixed with alkali aids. This material is most suitable for use with iron or steel slag, such as that which comes from a blast furnace or a steel-making process. The powdery silica-based solidification material mixed with iron and steel slag can be expected to exhibit higher mechanical strength and more predominant characteristics than a powdery cement-based solidification material. In this study, the solidification mechanism for the mixture of the silica-based solidification material, blast furnace slag and water is clarified from the viewpoints of chemistry and mineralogy by conducting X-ray diffraction analysis, X-ray fluorescence spectrometry and inductively coupled plasma spectroscopy.

  2. SOIL BEARING CAPACITY REFERENCE FOR METRO MANILA, PHILIPPINES Download Article

    Jonathan R. Dungca, Ismael Concepcion Jr., Moises Christian Mickhail Limyuen, Terence Oliver See4 and Marion Ryan Vicencio
    • Article Type: Research Article
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    • Pages (5-11)
    • No of Download = 1610

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    This study focuses on the analysis of the soil bearing capacities of the various cities and municipalities of Metro Manila, Philippines. The allowable soil bearing capacities to be used for foundation design were calculated through various theories and studies using geotechnical parameters, such as relative density and angle of internal friction. Standard Penetration Test (SPT) results were used to estimate these geotechnical parameters in order to obtain a good approximation of the soil‘s bearing capacity. Because of economic constraints, not all low-rise construction projects choose to perform soil exploration. Due to this, soil data are usually lacking and may cause problems when designing shallow foundations of these kinds of structures. In line with this kind of situation, the study can help engineers in designing shallow foundations by providing them a reference of the allowable soil bearing capacity of any area within Metro Manila. This will be able to give them a good idea of the soil‘s strength in supporting shallow foundations. The allowable bearing capacity of the soil shown in the reference is obtained from collected borehole data within Metro Manila and by using several geotechnical engineering theories. Contour maps of the bearing capacities are then made in order to provide an overview of the soil bearing capacity for shallow foundations. A Geographic Information System (GIS) software database was also made so as to store all the borehole location‘s data as well as serving another basis for estimation. This can be updated whenever new data is available.

  3. ASSESSMENT OF CRITICAL-STATE SHEAR STRENGTH PROPERTIES OF COPPER TAILINGS Download Article

    Erica Elice Saloma Uy and Mary Ann Q. Adajar
    • Article Type: Research Article
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    • Pages (12-18)
    • No of Download = 988

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    Philippines, with a total of 7,107 islands, have one of the largest mineral resources in the world. The copper and gold deposits are considered to be among the largest in the world (Bureau of East Asian and Pacific Affairs, 2010). Mining minerals generate waste material called mine tailings. Impoundment of mine tailings is normally done to store these waste materials. One of the most common types used in impounding tailings is raised embankments because of its low economic cost. This impoundment uses natural soil, tailings, and waste rocks as the construction material. There are cases that raise embankments experience stability failure which can affect the environment and well-being of the community where it is situated.
    It is the interest of this study to assess the possibility of using mine tailings, specifically copper tailings, as a construction material. Index properties were first established following ASTM standards. From this, it was established that the copper tailings has plasticity. Unconsolidated undrained, consolidated undrained and consolidated drained test were conducted to determine the critical shear strength of the copper tailing. The copper tailings were tested having two relative densities namely, 60% and 90%. The effective critical angle of friction was found to have a range of 21°-28°. Since critical-state parameters are considered in the study, Cam clay model can be implemented so that to its behavior and failure mechanism can be predicted.

  4. METHODS OF SUPPRESSING COLONIZING SEDGE TO HELP TO ESTABLISH TREE SEEDLINGS IN A NATURAL FOREST Download Article

    Teruo Arase, Tetsuo Okano and Tetsuoh Shirota
    • Article Type: Research Article
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    • Pages (19-24)
    • No of Download = 536

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    Dense bamboo grasses have delayed the growth of tree seedlings after the wind damage in a natural coniferous forest in deep mountains of Kiso District, Central Japan. After suppression treatment of the bamboo grass, a native sedge Carex oxyandra replaced them and made the growth of tree seedlings worse. The technique to suppress colonized Carex oxyandra is unknown, since this sedge has not ever been a harmful weed to be controlled. Thus, we established first experimental plots for suppressing Carex oxyandra by a herbicide, glyphosate potassium salt solution (Roundup Max load) by normal levels of dilution (control without herbicide, diluted to ×25, ×50 and ×100 volume with water) in May 2010. Next experimental plots with above-normal levels (diluted to ×100, ×200, ×400, ×800, ×1,600 and ×3,200) were established in June 2011. Coverage percentage, plant height of Carex oxyandra and tree seedlings were measured in each plot in autumn up to 2015. As a result, coverage and plant height of Carex oxyandra decreased obviously after a half year in all dilution levels, and the suppressing effect continued during 2 years in the lower dilution from ×25 to ×400. However, withered leaves formed a carpet-like thick mat, which remained several years and was suspected to restrict the germination and growth of tree seedlings. Consequently, the herbicide proved out effective to the sedge for 2 years, but some additional treatment is needed to secure the foundation space for tree seedlings within the mat of withered leaves.

  5. EFFECTS OF VERTICAL WALL BARRIER ON THE RIGID PAVEMENT DEFLECTION OF FULL SCALE 1-PILE ROW NAILED-SLAB SYSTEM ON SOFT SUB GRADE Download Article

    Anas Puri, Bambang Suhendro and Ahmad Rifa’i
    • Article Type: Research Article
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    • Pages (25-29)
    • No of Download = 416

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    The weaker part of rigid pavement when it is loaded is the edge of slab. Vehicle wheels that are often running in/out from/to pavement can cause void in the sub base-pavement interface for a long time loading period. Flexural moment caused by temperatures also precipitate the damages of pavement edge. To avoid the damage of pavement edge, the vertical wall barrier is added. This research is aimed to learn the contribution of vertical wall barrier on the pavement of Nailed-slab System to reduce the slab deflection. Full scale observation was done over models in soft clay soil. The full scale of 1 pile row Nailed-slab System was conducted on soft clay which consisted of 6.00 m x 1.20 m slab area with 0.15 m in slab thickness, 5 short micro piles as slab stiffeners which were installed under the slab. Piles and slab were connected monolithically, then in due with vertical concrete wall barrier on the two ends of slab. The system was loaded by compression loadings on the slab. Deflection of model without vertical wall barrier was analyzed by finite element method. Results show that the vertical wall barrier cannot significantly reduce the deflection for edge loading. It is opposite to the model test result from Puri, et.al. (2011) where the vertical wall barrier can reduce 74% deflection for edge loadings. It is to be expected that numerical application program could not model the vertical wall barrier which lower position than slab level.

  6. AN EVALUATION OF OSMOTIC TECHNIQUE UNDER ULTRAVIOLET GERMICIDAL IRRADIATION EXPOSURE Download Article

    Mohd Yuhyi Mohd Tadza, Nurhidayah Mahazam and Snehasis Tripathy
    • Article Type: Research Article
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    • Pages (30-36)
    • No of Download = 662

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    The osmotic technique, which uses polyethylene glycol (PEG) solutions of varying concentrations with semipermeable membranes of different molecular weight cutoffs (MWCO), is commonly used to apply suction in soils. Cellulose acetate membranes which are most commonly used, are susceptible to microbial attacks. This in turn will lead to the intrusion of PEG into soil specimens. Osmotic and vapour equilibrium techniques are often used to establish drying suction-water content soil-water characteristic curves (SWCC). In this study, suctions of 0.11 to 300 MPa were applied on Andrassy bentonite slurries. At higher applied suctions, the osmotic tests were carried under short length ultraviolet germicidal irradiation (UVGI). In addition, Atomic Force Microscopy (AFM) and Fourier Infrared (FTiR) were employed to evaluate the changes in the semipermeable membranes and PEG molecules, respectively. The water content of the clay obtained from the osmotic tests was found to be greater at the overlapping suction region. Interestingly, under UVGI exposure, the water content was found to be in good agreement with the water content determined using the osmotic technique at low suctions and the vapour equilibrium technique at higher suctions. FTiR spectrum and AFM results revealed that some changes had occurred on both the PEG and in the membrane pore sizes. However, these changes did not affect the final water content in the bentonite and therefore, more precise suction-water content SWCC for the clay could be established.

  7. REMOVAL OF ORGANIC MATTER IN WASTEWATERS OF A MILK FACTORY AND A HOSPITAL USING A CUBIC LATTICE BASED ROTATING BIOLOGICAL CONTACTOR IN VIETNAM Download Article

    Tatsuhide Hamasaki, Phan Do Hung and Hiroshi Tsuno
    • Article Type: Research Article
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    • Pages (37-42)
    • No of Download = 826

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    Pilot tests of a cubic-lattice-based rotating biological contactor were implemented to remove organic matter from wastewater from a milk factory and a hospital in Vietnam. In the milk factory wastewater, the biochemical oxygen demand (BOD) removal ratio was stable between 60% and 90% (average 75%) using this method, with a BOD surface load of 0.002–0.020 kg•m−2•day−1. The average nutrient ratio of the raw wastewater was 0.13 of total nitrogen and 0.015 of total phosphorus compared with 1.0 of BOD. The BOD of treated water was less than 50 mg•L−1, achieving category B of the industrial wastewater standard of Vietnam (QCVN 40:2011). For the hospital wastewater, the BOD removal ratio was stable between 60% and 90% (average 78%), with a BOD surface load of 0.005–0.022 kg•m−2•day−1. The average nutrient ratio of the raw wastewater was 0.25 of total nitrogen and 0.018 of total phosphorus compared with 1.0 of BOD. The BOD of treated water was less than 50 mg•L−1, satisfying category B of the medical wastewater standard of Vietnam (QCVN 28:2010/BTNMT). The electric power consumption was 0.73 KWh•m-3 of wastewater. The sludge conversion ratio from BOD was 0.51 kg TSS•kg BOD−1 based on the excess sludge and suspended solids in raw wastewater and treated water.

  8. INFLUENCE OF WEATHERING OF BOTTOM ASH ON THE LEACHING BEHAVIOR OF CESIUM Download Article

    *Yasumasa Tojo, Saori Iwamoto, Mikako Ishii, Toshihiko Matsuto and Takayuki Matsuo
    • Article Type: Research Article
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    • Pages (43-49)
    • No of Download = 825

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    After nuclear accident in 2011, incineration residue contaminated by radioactive cesium had been produced. Government decided in 2011 that incineration residue with less than 8000 Bq/kg of radioactivity could be disposed of into conventional MSW landfill. Since radioactivity of bottom ash was reported to be low compared with fly ash, it had been disposed of MSW landfill based on the government regulation. However, long-term leaching behavior of cesium contained in bottom ash when being disposed of into landfill was not known. Thus, in this study, phase transformation and leaching of cesium from incineration bottom ash were investigated by conducting accelerating weathering experiment. Four kinds of weathering condition were set; namely, blank (under nitrogen gas condition), wetting and drying, freezing and thawing, and exposure to carbon dioxide gas. Leaching of cesium under blank condition didn't change. On the other hand, drastic decrease of leaching of cesium was identified under carbon dioxide exposure. From XRD analysis, formation of calcite was identified. It was deemed that newly formed calcite inhibited the leaching of Cs by covering reactive surface of bottom ash. In both wetting-drying and freezing-thawing condition, leaching of Cs increased initially. But it decreased after several weeks then it became lower than blank finally. This decrease of leaching also seems to be caused by formation of calcite. Besides, in order to confirm the assumption in which the restrain of cesium leaching occurred by calcite formation, SEM-EDS analysis was performed. By the analysis, calcite formation on the surface was clearly identified.

  9. IMPACT ON AIR QUALITY BY INCREASE IN AIR POLLUTANT EMISSIONS FROM THERMAL POWER PLANTS Download Article

    Akira Kondo, Hikari Shimadera and Mai Chinzaka
    • Article Type: Research Article
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    • Pages (50-56)
    • No of Download = 711

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    The amount of thermal power generation has increased significantly in Japan since the Great East Japan Earthquake in 2011, resulting in increase in emissions of air pollutants. This research evaluated the impact of the emission increase on air quality in Kinki region, Japan by using the Community Multiscale Air Quality model (CMAQ) driven by the Weather Research and Forecasting model (WRF). Three cases of CMAQ simulations were conducted with emission data considering thermal power generation for the year 2010 and 2012, and without power plant emissions, using the meteorological field fixed to 2010.The simulation for the year 2010 well agreed with observations. The emission increase caused higher air pollutant concentrations around power plants, and the contribution of power plant emissions was up to 15 % of NO2 concentration in 2012.

  10. OCEAN DECONTAMINATION: HIGH ABILITY REMOVAL METHOD TO RADIOACTIVE CESIUM FROM OCEAN SLUDGE BY USING MICRO BUBBLES AND ACTIVATING MICROORGANISMS Download Article

    Kyoichi Okamoto, Takeshi Toyama and Tomoe Komoriya
    • Article Type: Research Article
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    • Pages (57-62)
    • No of Download = 633

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    The Fukushima nuclear accident of March 11, 2011, soil and water had been contaminated by radioactive cesium. Moreover, radioactive cesium was found in the ocean sludge in Tokyo Bay flowing from rivers. Cesium which is adsorbed to the sludge cannot be easily removed. One of the authors developed decomposition and purification system, a circulation-type system by micro bubbles, that is, by creating aerobic state, aerobic bacteria are activated resulting to decomposition and purification of ocean sludge. Based on the hypothesis that radioactive cesium is adsorbed on the surface of the sludge deposition. It is considered that cesium can be eluted after decomposing the deposited sludge. Once the cesium is eluted in the water, it can fix to a mineral such as zeolite. Eluting and fixing cesium adsorbed on sludge takes so much time. In this case, the concept of removing the left sludge by flocculation method and then followed by coagulating sedimentation method is studied. In this study, our objects is to show the effectivity and efficiency of using flocculation and coagulating sedimentation in removing radioactive cesium. As the results, we pointed out this method is very good.

  11. AIR PRESSURE DISTRIBUTION INDUCED BY RAINFALL INFILTRATION IN SOIL/WATER/AIR COUPLED SIMULATION Download Article

    Katsuyuki KAWAI, Takuya KAWAKATSU and Ayumi TERAOKA
    • Article Type: Research Article
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    • Pages (63-69)
    • No of Download = 686

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    Recently, the frequency of torrential rainfall has increased due to global climate change, and these events cause sediment potential failure. It is difficult to predict when and where a slope failure will occur because of the concentration of heavy rain. Knowing precursory phenomena, however, is effective for disaster reduction. Nonetheless, some of these phenomena have not been explained in the framework of geotechnical engineering. Organic smells and strange sounds, known as precursory signs of slope failure, propagate through the atmosphere. Therefore, it is important to monitor air movement within earth structures. This study focuses on pore air behavior within the ground due to rainfall infiltration. Here, the infiltration column test combined with monitoring smell, as conducted by Tsuchida et al., was first simulated using the soil/water/air coupled finite element code, DACSAR-MP. Next, a sloping earth structure exposed to rainfall was simulated. Consequently, it was found that distribution of pore air pressure was dependent on drainage conditions of air, and that pore air behavior influenced rainfall infiltration behavior.

  12. A STUDY ON GROUND IMPROVEMENT TECNIQUE WITH IN-SITU MICROOGANISMS ISOLATED FROM JAPAN Download Article

    Rusutsu Ito and Toshiro Hata
    • Article Type: Research Article
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    • Pages (70-75)
    • No of Download = 657

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    Damage by a liquefaction phenomenon was a problem in recent years, and the Great East Japan Earthquake occurred on March 11, 2011 in Japan, and liquefaction damage occurred frequently. There is also more adoption of Paris agreement in COP21 of the end of last year, and correspondence to a global warming problem is also desired reduction in greenhouse effect gas amount of emission in the construction field. Therefore considered ground improvement technology is necessary for the environment in Japan an earthquake-ridden country. So we considered for practical use ground improvement techniques based microorganism. That is watched as new liquefaction countermeasure technology for reduction in cost and the point of view by which material and construction waste are reduction. In that ground improvement techniques, it is difficult to using specific microbes. So we aimed at Microbial carbonate precipitation using in-situ microorganism as the method to solve this problem. We made solidify sand using isolated microorganisms in japan and Bacillus pasteurii the solidification ability becomes clear. We measured to urease activity values of each microorganism. And we making of the test pieces, undrained cyclic triaxial test and acid decomposition for using CaCO3(0.5mol/L). And we compared results. We understood two things from examination results. 1) The difference occurs to liquefaction strength by urease activity value. 2) The improvement effect of the liquefaction strength was admitted in Microbial carbonate precipitation using in-situ microorganisms in the spots selected by this research.​

  13. CYCLIC LATERAL RESPONSE OF MODEL PILE GROUPS FOR WIND TURBINES IN CLAY SOIL Download Article

    Werasak Raongjant and Meng Jing
    • Article Type: Research Article
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    • Pages (76-81)
    • No of Download = 765

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    Due to the large diameter and the cyclic loading, it is necessary to investigate the lateral response of pile groups for wind turbines in clay soil. This paper presents an experimental research on 2x2 model pile groups embedded in different types of clay soil, relatively density of 90% and 10%, subjected to one-way lateral cyclic loading. Analysis on the experimental results, such as load–deflection curves and bending moment profiles, were processed. It is found that the magnitude of the head level deflections and the maximum bending moment increased with the number of loading cycles. The group interaction effect under cyclic lateral loading is more significant in loose soil.​

  14. A STUDY ON THE USE OF POLYURETHANE FOR ROAD FLOOD DAMAGE CONTROL Download Article

    Safawati Mohd Radzi, Abdul Naser Abdul Ghani, Muhd Shahril Nizam Ismail, Ahmad Hilmy Abdul Hamid and Khalid Ahmad
    • Article Type: Research Article
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    • Pages (82-87)
    • No of Download = 718

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    The strength of subgrade soil or road foundation could influence the design of road pavement structures. Flood can be one of the causes of weakened subgrade and consequently road damages. Since the condition of subgrade layer is critical in the road pavement stability, a preliminary study was carried out to ascertain the use of polyurethane insertion as a stabilization mechanism in road subgrade. This study was conducted based on two types of soil that are usually used as soil embankment in road construction. California Bearing Ratio (CBR) test was conducted on the various categories of soaking days and repeated submerged conditions to determine the strength of subgrade soil with and without polyurethane layer. It can be concluded that polyurethane layer can be used to increase or maintain the strength of subgrade soil from the inundation effect.​

  15. A STUDY OF RESTRAINT TECHNIQUES FOR CEMENT TREATED SOIL’S DETERIORATION BY MICROBIAL FUNCTIONS Download Article

    Kazuki Mihara and Toshiro Hata
    • Article Type: Research Article
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    • Pages (88-93)
    • No of Download = 790

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    Cement treated soil is used as a countermeasure for poor ground. But, cement treated soil deteriorate by calcium leaching because of exposing seawater. This study considered a technology of reducing deterioration of cement treated soil by using urease-producing bacteria. Authors tested seawater exposure tests using 2 types of the urease-producing bacteria of Sporosarcina aquimarina isolated from the sea off the coast of Korea and Bacillius pasteurii isolated from land. The purpose of those tests is checking effect of reducing deterioration of cement treated soil by the urease-producing bacteria. At the same time, we performed tests to confirm the growth of the bacteria in cement treated soil. We tested seawater exposure tests 2 types of conditions of temperature 20℃ is used for exposure tests, and 30℃ is a temperature that is suitable for the growth of bacteria, the purpose of those tests is checking relation temperature and deterioration speed. The main outcomes are as follows: 1) 2 types of the urease-producing bacteria have an ffect of reducing deterioration 2) 2 types of condition of temperature have relation to deterioration speed.​

  16. EFFECTS OF TEMPERATURE ON ELASTIC STIFFNESS OF A HDPE GEOGRID AND ITS MODEL SIMULATION Download Article

    Thitapan Chantachot、Warat Kongkitkul and Fumio Tatsuoka
    • Article Type: Research Article
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    • Pages (94-100)
    • No of Download = 690

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    One of the important factors that affect the mechanical properties of polymer geosynthetic reinforcement is the ambient temperature. With an increase in the temperature, the rupture strength and the elastic stiffness decrease. In this study, to understand the temperature effects on the load-strain-time behaviours of a polymer geogrid, a series of tensile loading tests were performed on a high-density polyethylene (HDPE) geogrid at different but constant temperatures, and also under step-increasing temperature conditions. The test results revealed that the elastic stiffness of tested geogrid increases with the load level, while decreases with the ambient temperature. These properties were modelled based on the framework of hypo-elasticity. An existing non-linear three-component (NTC) model, which can simulate the load-strain-time behaviours of many types of polymer geogrid subjected to arbitrary loading histories (e.g., monotonic loading at different rates, creep or sustained loading, load relaxation) under a constant temperature, was modified to account for the dependency of the elastic stiffness on the load level and the temperature, as well as the dependency of the rupture strength on the temperature. The modified model can simulate very well the observed temperature effects on the elasticity of the tested geogrid.

  17. REMOVING FLUORIDE FROM A HOT SPRING USING AN ELECTROLYSIS SYSTEM Download Article

    Yuki Imai, Shiori Yanagawa, Misa Konishi and Tomonori Kawakami
    • Article Type: Research Article
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    • Pages (101-106)
    • No of Download = 603

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    A high concentration of fluoride in the wastewater from hot springs is an environmental issue in Japan, since some of the wastewater exceeds the national minimum effluent standards of 8 mg/l. However, an effective treatment for fluoride removal has not yet been developed. Accordingly, the temporal effluent standards of 15mg/l - 50 mg/l have, so far, been applied to the wastewater from hot springs.
    In this study, an electrolysis system consisting of an anode bath and a cathode bath separated by a diaphragm made of a clay panel was tested for the removal of fluoride. In an electrolysis system, fluoride is removed by co-precipitation with magnesium hydroxide formed in a cathode bath under a high pH condition.
    As a pretreatment of wastewater, 100 mg/l of magnesium was added to water from Gero hot spring, Gifu, Japan, to enhance the formation of the precipitation of magnesium hydroxide, since water from Gero hot spring contains less than 1 mg/l of magnesium. Water from Gero hot spring to which 100 mg/l of magnesium had been added was treated by an electrolysis system with a flow rate of 10 l/day and a current of 120 mA. The electrolysis system reduced the fluoride concentration from 16.6 mg/l to 6.4 mg/l, which meets the national minimum effluent standards of 8 mg/l.

  18. USE OF CBR MOULD FOR EVALUATION OF CONSTRAINED MODULUS-BULK STRESS RELATIONS OF PAVEMENT STRUCTURE MATERIALS Download Article

    Sawanya Dararat and Warat Kongkitkul
    • Article Type: Research Article
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    • Pages (107-113)
    • No of Download = 2030

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    One of important parameters used in the mechanistic pavement engineering design is resilient modulus (MR) of pavement structure materials. In general, MR is evaluated in a complicated and thus expensive triaxial compression test in that a number of repeated loads are applied at various stress states. This research presents an alternative method to determine the constrained modulus (M) of a dried sand, a lateritic soil and a crushed rock, under one-dimensional compression. At various vertical stress levels, M values were determined by applying small strain-amplitude cyclic loadings to the compacted soil specimens prepared in a CBR mould. In the present study, the CBR mould was made special in that it can measure the lateral stress confining to the specimen during a test. Hence the bulk stress can then be determined, and M-bulk stress relations for the tested materials were presented. In addition, an analytical method for eliminating the effects of bedding error was
    attempted so as to obtain the true M value. It is found that M is not constant but increases with bulk stress, similar to MR-bulk stress relations found with the resilient modulus test. In addition, the bedding error is important and can result in a significant underestimation of the true M value.

  19. EVALUATING THE DYNAMICS OF ALIEN SPECIES (POACEAE) USED FOR EROSION CONTROL ON SAKURAJIMA VOLCANO Download Article

    Taizo Uchida, Jun Tanaka, Kentaro Kondo, Daisuke Hayasaka, Yuki Tomoguchi, Teruo Arase and Tetsuo Okano
    • Article Type: Research Article
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    • Pages (114-120)
    • No of Download = 622

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    Alien species in the family Poaceae play an important role as cover plants for erosion control on slopes, particularly in Japan. However, concerns have arisen regarding the adverse effects of these species on the local ecosystem and biodiversity. This study therefore examined the succession and seed propagation of alien Poaceae that are used for erosion control on the cut slopes of Sakurajima volcano in southwestern Japan. The results were as follows: Although the alien species used as cover plants were dominant for the first couple of years following their introduction to the slopes, they were displaced entirely by native species after the sixth year, which is considerably faster than ordinary succession. In addition, heading (flowering) of alien species was also rarely observed in this period. It is considered that the observed results were caused by the oligotrophic conditions of the slopes on Sakurajima volcano.

  20. EFFECT OF ADDITION OF BACTERIA ON THE REMOVAL OF RADIOACTIVE CESIUM FROM OCEAN SLUDGE IN A CIRCULATION TYPE PURIFICATION SYSTEM Download Article

    Tomoe KOMORIYA, Kyoichi OKAMOTO and Takashi TOYAMA
    • Article Type: Research Article
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    • Pages (121-126)
    • No of Download = 683

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    Following the Fukushima nuclear accident of March 11, 2011, soil and water were contaminated by radioactive cesium. Moreover, radioactive cesium was found in the ocean sludge in Tokyo Bay, carried by rivers flowing into the bay. The cesium adsorbed in the sludge cannot easily be removed. The objective of this study was to investigate the effect of the addition of bacteria to the micro-bubble circulation system on the efficient removal of radioactive cesium from ocean sludge. One of the authors has developed an ocean sludge decomposition system employing circulation of micro-bubbles. Model sludge was prepared using seawater, sea sludge, and cesium chloride. Bacteria were added to the system after 24 h. Dried tangle extract was added as a nutrient at 24 h and 36 h. The decomposition experiment was carried out for 120 h. The circulation of micro-bubbles created an aerobic state that activated aerobic bacteria, facilitating decomposition and purification of the sludge. Thus, decomposition of the deposited sludge using our system renders the elution of the radioactive cesium possible. If the cesium is eluted in the water, we can fix it using existing technology such as zeolites. We identified and isolated the most useful bacteria for sludge decomposition. Effects on purification seem to be greatest when additional bacteria are added directly to the process. The methodology proposed is expected to facilitate decomposition of sludge and removal of radioactive cesium from the environment.

  21. A MESOSCALE INVESTIGATION ON THE SIZE EFFECT OF THE FRACTURE CHARACTERISTICS IN CONCRETE Download Article

    N. Aissaoui and M. Matallah
    • Article Type: Research Article
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    • Pages (127-133)
    • No of Download = 525

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    The size effect or scaling phenomenon is a fundamental problem when dealing with fracture of geomaterials. Concrete is considered as one of world’s most widely used construction materials. The design in civil engineering of structural concrete should take into account the size effect when extrapolating the experimental tests at laboratory scale to structures with large dimensions. The size effect is generally investigated on the nominal strength which is an important parameter for design in civil engineering. However, the fracture characteristics are also considered in structural concrete codes. The limitation of cracking (crack width, crack length , etc. ) are important aspects to consider in order to guarantee a safe conception. This paper deals with a numerical analysis of size effect on the nominal strength and on the cracking characteristics in concrete beams. Numerical simulations of geometrically similar notched beams of various sizes are performed using a mesoscopic approach with an isotropic damage model. In order to properly describe the cracking process, a post processing method based on the fracture energy regularization is adopted. The size effect on crack-opening and crack length evolution is investigated by comparing the numerical results with experimental data obtained by digital image correlation technique. The numerical results prove the ability of the mesoscopic approach to describe the size effect on the global behavior and the local behavior of concrete. The numerical investigation reveals the existing of a size effect on the cracking process evolution.

  22. EFFECT OF PILE CONNECTIONS ON THE PERFORMANCE OF THE NAILED SLAB SYSTEM ON THE EXPANSIVE SOIL Download Article

    Willis Diana, Hary Christady Hardyatmo and Bambang Suhendro
    • Article Type: Research Article
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    • Pages (134-141)
    • No of Download = 866

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    Expansive soils are clay that swells and shrinks with changing moisture content. The pavement that constructed on these soils is subjected to large uplifting forces caused by swelling. Hence, there is an imperative need to counteract the problem posed by these soils by devising innovative pavement technique. An attempt to develop a simple, easy to install and cost-effective alternative pavement system, nailed slab system was developed, wherein slab pavement will be connected to a reinforced concrete mini piles.This research examines the emerging role of mini piles in the context of reducing soil uplift movement and the nailed slab system (pile supporting slab pavement) a system for minimizing slab movement due to swelling in expansive soil by conducting small-scale experimental modeling in laboratories. The heave prediction also doing by using the correlation between change in moisture content and vertical strain from oedometer test data. The results of this study indicate that reinforcing the soil by using the mini piles can reduce heave of soil, and the nailed slab system experiencing smaller upward movement than an unsupported slab. The connection between the pile and the slab has a significant effect on the system’s ability to withstand the upward movement of expansive soil. When pile and the slab were monolithically connected, the system shows the better performance than those the slabs with the free head pile. Thereafter a heave prediction analysis provided the amount of heave that slightly overestimates, but still good enough for a rough estimation.

  23. DIGITAL IMAGE AND REMOTE SENSING IMAGE AS A DATA FOR AN IDENTIFICATION OF A QUALITY OF A NON-POINT SOURCE POLLUTANT IN CILIWUNG RIVER, INDONESIA Download Article

    Riki Mukhaiyar
    • Article Type: Research Article
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    • Pages (142-151)
    • No of Download = 761

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    The fact that the quality of water in the river is getting worse, especially for Ciliwung River which is contaminated with non-point source pollutant from household wastes, particularly on the downstream of Ciliwung River cannot be lied. But, by using technology of remote sensing, integrated with information from the data of digital image and modeling technology for the simulation of water quality will provide easiness during the observation on the quality of water changes on the river surface. One example of it is that the use of land for settlements and housing ranges between 62.84% - 81.26% on the downstream of Ciliwung River, give a significant picture in seeing factors that affected the water quality of Ciliwung River.

  24. SEISMIC MICROZONATION STUDIES CONSIDERING LOCAL SITE EFFECTS FOR YOGYAKARTA CITY, INDONESIA Download Article

    Teuku Faisal Fathani and Wahyu Wilopo
    • Article Type: Research Article
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    • Pages (152-160)
    • No of Download = 885

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    An Mw 6.3 earthquake hit Yogyakarta, Indonesia in 2006, causing massive damage in this densely populated area. As a consequence, risk reduction efforts in terms of local seismic response and peak ground acceleration (PGA) mapping is needed to improve the spatial planning and early assessment before another disastrous earthquake. The determination of PGA for microzonation study was conducted by referring to the Indonesian seismic code and empirical prediction by examining attenuation relationships considering the local site effects. The site investigation was conducted at 87 locations, comprising 13 core drillings and 74 microtremor measurements. Further, the nonlinear earthquake site response analyses were conducted to calculate the local seismic response occurring in a layered soil. Referring to the seismic code with a 2% probability of exceedance in 50 years and site characteristics, the maximum considered earthquake geometric mean PGA for Yogyakarta City is 0.50-0.57g, while the southern area has higher PGA. The empirical prediction by attenuation relationships that considers the 6.3 Mw Yogyakarta earthquake 2006 with 50-100 year return period resulted in PGA of 0.14g to 0.21g. Meanwhile, the empirical prediction based on soil predominant period resulting from microtremor measurements shows that the southern part of the city has higher PGA of 0.2g to 0.3g whereas the northern part has lower PGA of 0.1g to 0.2g. The result of nonlinear earthquake site response analyses shows that the PGA at the southern part and the northern part of the city have higher PGA up to 0.38g. The results show the significance of local site effects and site response analysis in determining the earthquake characteristics in comparison to the present simplified empirical approach.

  25. EVALUATION OF TIME RATE OF SWELLING PRESSURE DEVELOPMENT DUE TO THE PRESENCE OF SULFATE IN CLAYEY SOILS STABILIZED WITH LIME Download Article

    Pakbaz, M. S. and Keshani A.
    • Article Type: Research Article
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    • Pages (161-165)
    • No of Download = 684

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    The purpose of this study was evaluation of magnitude and time rate of swelling pressure due to the presence of gypsum in clayey soils stabilized with lime. 3,5 and 10 % of lime by dry weight and 0, 5 and 10 % of gypsum (calcium sulphate) were added to a bentonite. Then uncured and cured as compacted samples of mixtures were tested one dimensionally for constant volume swelling pressure measurement. The results showed that only samples treated with 3 and 5% lime without curing and with 7 days of curing showed initial increase in the magnitude of swelling pressure due to the presence of gypsum as compared with untreated bentonite or with bentonite treated with lime only. In fact samples with higher content of lime and gypsum which cured for 7 days or more actually showed lower swelling pressure compared with untreated samples.

  26. MECHANICAL PROPERTIES AND THERMAL BEHAVIOUR OF TWO-STAGE CONCRETE CONTAINING PALM OIL FUEL ASH Download Article

    A.S.M. Abdul Awal, Mohd Haziman Wan Ibrahim, Ahmad Zurisman Mohd Ali and M. Zakaria Hossain
    • Article Type: Research Article
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    • Pages (166-175)
    • No of Download = 842

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    Two-stage concrete (TSC) is a special type of concrete which is made by placing coarse aggregate in a formwork and injecting a grout either by pump or under the gravity force to fill the voids. Over the decades, the application of supplementary cementing materials in conventional concrete has become widespread, and this trend is expected to continue in TSC as well. Palm oil fuel ash (POFA) is one of the ashes which has been recognized as a good pozzolanic material. This paper presents the experimental results on the performance behaviour of POFA in developing physical and mechanical properties of two-stage concrete. Four concrete mixes namely, TSC with 100% OPC as a control, and TSC with 10, 20 and 30% POFA were cast, and the temperature growth due to heat of hydration and heat transfer in the mixes was recorded. It has been found that POFA significantly reduced the temperature rise in two-stage aggregate concrete and delayed the transfer of heat to the mass of concrete. The compressive and tensile strengths, however, increased with the replacement of up to 20% POFA. The results obtained and the observation made in this study suggest that the substitution of OPC by POFA is beneficial, particularly for prepacked mass concrete where thermal cracking due to extreme heat rise is of great importance.