Articles

  1. Application of PML to Analysis of Nonlinear Soil-Structure-Fluid Problem Using Mixed Element Download Article

    Pahaiti Reheman and Hiroo Shiojiri
    • Article Type: Research Article
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    • Pages (505-510 )
    • No of Download = 567

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    Mixed element may be conveniently used to express non-linear constitutive equation of fluid and to avoid volumetric locking. X-FEM may be well suited to model discontinuity of displacements between solid and fluid. Appropriate boundary conditions should be set at the boundaries of numerical models not to reflect outgoing waves. In this paper, complex frequency shifted convolution-PML without splitting of variables is developed for mixed element, and the performances of PML are confirmed. The formulation of PML is completely consistent with corresponding FEM or X-FEM. It can be easily extended to any type of element and any nonlinear constitutive equations of the corresponding FEM or X-FEM. The resulting mass and stiffness matrices for PML are symmetric for linear models.

  2. Lower Bound Limit Analysis of Strip Footings Resting on Cohesive Soils Download Article

    S.M. Binesh and A. Gholampour
    • Article Type: Research Article
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    • Pages (511-515 )
    • No of Download = 562

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    A Novel lower bound approach is presented for the bearing capacity determination of strip footings resting on cohesive soils. The approach consists of the combination of lower bound limit theory and a mesh-free technique. In the presented method there is no need of mesh in the traditional sense and the constraints at the element discontinuities are omitted. A statically admissible stress field is constructed by the combination of mesh-free technique and the nodal integration scheme. The generated field is guaranteed to be lower bound by controlling the non-yielding condition at the entire domain. The solutions of the presented approach are compared with some well-known solutions, to demonstrate the efficiency and accuracy of the method.

  3. Damage Assessment and Strengthening of R/C Building Constructed on Expansive Soils Download Article

    Osama M. A. Daoud
    • Article Type: Research Article
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    • Pages (516-521 )
    • No of Download = 1344

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    This paper presents an experience in assessment and strengthening of a R/C building carried out in Sudan during the last year. A four-story R/C framed hospital building was constructed five years ago in the middle of Sudan, by the White Nile River. Due to differential upheaval movement of the underneath expansive clay soils (15-25cm), the building had experienced serious instability problems and severe structural cracks. A comprehensive assessment of the building skeleton including geotechnical investigation, DT and NDT methods revealed the need of five different strengthening and retrofitting techniques; there are, transformation of foundation system from isolated footings to strap foundation to increase the stiffness and rigidity of footings, concrete jacketing of basement floor columns, metal jacketing of the second floor columns, construction of shear walls to enhance the stability of the building and finally CFRP laminates for strengthening of basement floor cover slab. The building had been monitored during and after completion of strengthening and retrofitting works to measure any movements during the last year rainy season. Measurements revealed the efficiency of implemented strengthening and retrofitting techniques.

  4. Development of Piled Geo-wall (A new type reinforced soil wall) Download Article

    Takashi Hara, Shinichiro Tsuji, Masaki Yoshida and Kazuhide Sawada
    • Article Type: Research Article
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    • Pages (522-527 )
    • No of Download = 1135

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    This study aims to achieve a new type of independent reinforced soil wall (Piled Geo-wall) that can be substitute for one made up of concrete with similar scale, and to contribute to sustainable development. In order to confirm the practicability of the novel structure, three experimental studies with static and impact loading tests and a dynamic centrifuge model test were carried out in the past years. Simple design methods of the novel structure, which can reproduce the results of the experiments, are introduced in this paper.

  5. Evaluation of Soil Water Characteristic Curves of Sand-Clay Mixtures Download Article

    T. Y. Elkady1, M. A. Dafalla, A. M. Al-Mahbashi and Mosleh Al Shamrani
    • Article Type: Research Article
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    • Pages (528-532 )
    • No of Download = 1155

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    This paper presents an experimental investigation performed to evaluate the soil water characteristic curves of sand/Al-Qatif clay mixtures.  Al-Qatif clay is natural expansive clay widely spread in the eastern province of Saudi Arabia. Detailed mineralogical and physical tests were performed on Al-Qatif clay for characterization.  Mixtures of sand and Al-Qatif clay were prepared with sand being the base material and with different clay contents (0%, 5%, 10% and 15%).  Test results indicate that the shape of SWCC curves changes from the unimodel to the bimodal form of soil water characteristic curve with the increase in clay content indicative of changes in sand/clay mixture micro-and macro-pores.

  6. Lime Stabilization of Tropical Soils From Sudan For Road Construction Download Article

    Ahmed M. Elsharief, Adil A. M. Elhassan, Awad E. M. Mohamed
    • Article Type: Research Article
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    • Pages (533-538 )
    • No of Download = 1592

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    The objective of this paper is to study the effects of hydrated lime on the engineering properties of interest for road design and construction for three tropical clays, two highly plastic potentially expansive soils from Republic of Sudan and one red tropical “lateritic” soil from Republic of South Sudan. The studied properties include Atterberg limits, compaction parameters, permeability, CBR, MR and unconfined strength. The effects of compaction energy on the end result compaction material property parameters were studied. Also, the effect of salinity/sodicity on the plasticity and strength of lime stabilized swelling soils was studied. The study showed that lime efficiently reduces the plasticity of the three soils considered and that for the same increment of lime content the reduction in plasticity is higher for montmorillonitic clays compared to kaolinitic clays. The addition of lime to the three soils increased their maximum dry density and reduced their optimum moisture content. Substantial improvement in the strength and compaction characteristics of lime stabilized tropical clays could be expected on increasing the compaction effort. Permeability substantially increased on adding the optimum lime content to the three soils. Lime increased the strength and stiffness of the treated soils and the amount of lime needed to improve lateritic clay soils is less than that needed to improve swelling soils. The MR test results indicate increased stiffness of the lime stabilized kaolinitic clay soils compared to montmorillonitic clays. The increase in salinity/sodicity resulted in decrease of plasticity and increase in strength for the natural untreated and lime treated sodic soil tested.

  7. Production and Properties of High Strength Concrete for Heightening Concrete Dam in Sudan Download Article

    Sudan by Osama M. A. Daoud and H. S. Sagady
    • Article Type: Research Article
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    • Pages (539-545 )
    • No of Download = 8230

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    This paper presents a part of an ongoing experimental laboratory investigation being carried out for production and characterization of high strength concrete (HSC) for heightening of an existing concrete dam in the middle of Sudan. Brief description of the main features of the dam and concrete works is presented. Hundreds of trial mixes were performed and tested using local Sudanese aggregates with addition of mineral admixtures (Silica Fume and Fly Ash) and Super plasticizers. Six grades of HSC (50, 60, 70, 80, 90, 100 MPa) had been success fully produced and their mechanical properties were measured and documented. Statistical analysis of tests results was performed and simple correlations were developed relating compressive strength to flexural and Splitting Strengths. The results have offered an important insight for optimizing the rheological characteristics of HSC and permitted to develop guidelines for optimum mix design methods for HSC from locally available aggregates in Sudan. The effect of w/c ratio on strength of HSC was also highlighted. It is concluded that local concrete materials, in combination with mineral admixtures can be utilized in producing High Strength Concrete in Sudan.

  8. Physical and Mechanical Properties of Sand-Gravel Mixtures Download Article

    Janaka Kumara, Kimitoshi Hayano, Yuuki Shigekun and Kota Sasaki
    • Article Type: Research Article
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    • Pages (546-551 )
    • No of Download = 2133

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    In railway tracks, ballast fouling due to fine materials mixing has been identified as a challenging issue. In this research, deformation characteristics of sand-gravel mixtures, simulating fine-ballast mixtures, were studied using laboratory and DEM-simulated triaxial compression tests. The DEM simulations were done in Yade, an open source developed based on DEM. Initially, void ratio characteristics of sand-gravel mixtures were studied. Then, triaxial compression tests were conducted for the specimens of 50% and 80% of relative densities. The void ratio results indicated that, initially, void ratios decreased with %sands. After reaching the minimum void ratios, void ratios increased with %sands. The triaxial test results indicated that, on average, similar behaviour in stress-strain curves, where, at initial %sands, stress-strain curves became higher and then, stress-strain curves became smaller, though it was slightly different in laboratory tests.

  9. Characterization and Demonstration of Reuse Applications of Sewage Sludge Ashes Download Article

    Brett Q. Tempest and Miguel A. Pando
    • Article Type: Research Article
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    • Pages (552-559 )
    • No of Download = 1199

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    In this paper sewage sludge ash (SSA) refers to ash material product of incineration of municipal and industrial sewage water.  SSA from a waste water treatment plant in Eastern United States was characterized in order to investigate and demonstrate potential reuse applications for the ashes produced by this plant.  To date most research on reuse applications for ash materials has focused largely on coal-sourced ashes such as fly ash or bottom ash.  In contrast very little research has been reported on SSA, which typically will have important differences with coal-based ashes in terms of physical and chemical composition and cementitious properties. This paper presents the results of an elemental and morphological characterization as well as a demonstration of clay brick admixture and soil stabilization admixture reuses applications.

  10. Prediction of the Axial Bearing Capacity of Piles by SPT-based and Numerical Design Methods Download Article

    Issa Shooshpasha, Ali Hasanzadeh and Abbasali Taghavi
    • Article Type: Research Article
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    • Pages (560-564 )
    • No of Download = 691

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    The prediction of the axial capacity of piles has been a challenge since the beginning of the geotechnical engineering profession. In recent years determining bearing capacity of piles from in-situ testing data as a complement of static and dynamic analysis has been used by geotechnical engineers. The Standard Penetration Test (SPT) is still the most commonly used in-situ test and pile capacity determination by SPT is one of the earliest applications of this test. On the other hand, the acceptance of numerical analyses in geotechnical problems is growing and finite element calculations are more and more used in the design of foundations.  In this paper, different approaches for estimating the bearing capacity of piles from SPT data have been explained and compared with numerical method. Then, comparisons between numerical and empirical results are presented and discussed.

  11. Measurement of Strain Distribution along Precast Driven Pile During Pile Load Test Download Article

    Faisal Ali and Lee Sieng Kai
    • Article Type: Research Article
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    • Pages (565-573 )
    • No of Download = 2272

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    One of the basic parameters required for forecasting pile deformation under loads is the characteristics and profile of the shaft load transfer from the pile to the surrounding soil.  This parameter can be obtained by measuring the strain distribution along the pile during full-scale pile load test.  For cast-in situ bored pile, the strain measurement can be easily done by fixing the sensors to the reinforcement cage before pouring the concrete. For precast driven / jack-in piles, the application of instrumented full-scale static load tests is far more challenging than their bored pile counterparts due to significant difference in method of pile installation. Due to practical shortcoming of conventional instrumentation method instrumented full-scale static load tests are in fact rarely used in driven pile application in this region.  For hollow precast spun concrete piles attempts have been made by geotechnical engineers to measure the strain distribution by installing either an instrumented reinforcement cage or instrumented pipe into the hollow core of spun piles followed by cement grout. However in this method, known as approximate method, the measured characteristics cannot be considered to represent the working piles because the presence of reinforcement/pipe and the grout would alter the stiffness of the test pile.  In this paper a method to measure the strain distribution along the installed precast spun concrete pile during full-scale pile load test is described. The method utilizes the hollow core of the spun pile without changing the physical properties e.g. stiffness, of the pile. The main advantages of this method are: the measurement can be done at any location along the pile, the sensors can be retrieved and the measured characteristics are representative of those of the working piles.

  12. Purification System of Ocean Sludge by Using Coagulants and Activating Microorganisms Download Article

    Kyoichi Okamoto and Kenji Hotta
    • Article Type: Research Article
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    • Pages (574-579 )
    • No of Download = 630

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    Ocean sludge exerts a very big environmental load to local sea area. Here, attention was paid to micro-bubble technology for application to the purification of the sludge. The important point in this technique is to activate the bacteria existing in the area by micro-bubbles. We had developed a method for decomposing the sludge by using of microorganisms in an aerobic state by micro-bubble. Here, we have also a technique for purification by using “coagulants”.  So, we proposed the experimental way which hydrogen sulfide is reduced at first by using “coagulants” and then the nutrients will be reduced by activating microorganisms. Here, we used the detergents including enzyme as the microorganism activator. Our research object in this paper is to check the purification performance for sludge by our proposed experimental system. From the results of our experiments, we succeeded in reducing the time needed to purify the sludge, and we obtained the very good performance.

  13. Fundamental Study on Ecosystem Support Canal using Porous Concrete Download Article

    Shushi Sato, Yoshihiro Masuma, Yuki Hasegawa, Man-Kwon Choi and Hirohumi Kassai
    • Article Type: Research Article
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    • Pages (580-584 )
    • No of Download = 555

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    This research aimed to enhance the compressive strength of porous concrete as well as to develop the porous concrete that can support and improve the ecosystem preservation by itself. Several porous concrete specimens were prepared for the measurement of mechanical properties. As a result, it was confirmed that the radius of coarse aggregate affected significantly to mechanical properties of porous concrete under the same unit weight of cement. It was also revealed that strengths at age 28 days were stable despite of different sizes of coarse aggregate. The bio-adhesive ability of porous concrete specimen was evaluated against water bugs and adhesive algae. Every porous concrete specimen was soaked in same environmental condition at the bottom of actual concrete canal. From this experiment, it was confirmed that preference environment for some specific species of water bugs are possible to be supplied when the porosity and the size of coarse aggregate would be adjusted.

  14. Scale Effects of Plate Load Tests in Unsaturated Soils Download Article

    Won Taek Oh and Sai K. Vanapalli
    • Article Type: Research Article
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    • Pages (585-594 )
    • No of Download = 1774

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    The applied stress versus surface settlement (SVS) behavior from in-situ plate load tests (PLTs) is valuable information that can be used for the reliable design of shallow foundations. In-situ PLTs are commonly conducted on the soils that are typically in a state of unsaturated condition. However, in most cases, the influence of matric suction is not taken into account while interpreting the SVS behavior of in-situ PLTs. In addition, the sizes of plates used for load tests are generally smaller in comparison to real sizes of footings used in practice. Hence, in-situ PLT results should be interpreted taking account of not only matric suction but also the scale effects. In the present study, discussions associated with the uncertainties in interpreting the SVS behavior of PLTs taking account of matric suction and scale effect are detailed and discussed.