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RISS 인기검색어
- 검색키워드
- 저자 : Hossein Salehzadeh (검색결과 4 건)
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Habib Shahnazari,Hossein Salehzadeh,Reza Rezvani,Yasser Dehnavi 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.4
Laboratory research was conducted to compare the monotonic behavior of two different marine calcareous sands - Hormuz Island(HI) and Bushehr Port (BP) - with siliceous sand named Firoozkuh sand (F). A series of undrained isotropically consolidated triaxialtests was performed on reconstituted specimens of these sands. In this experimental investigation, their contractive and dilativebehaviors were evaluated. The effect of some important parameters, such as relative density and confining pressure on the behaviorof these specimens was studied. To analyze the effect of shape and stiffness (resistance to particle breakage) on the contractive andthe dilative responses of these soils, the influence of axial strain on the crushability of the calcareous soils was assessed. Thereafter,the undrained behavior of the soils was analyzed, using two parameters, which represented a normalized variation of excess porewater pressure in two phases of monotonic triaxial tests. The contractive and dilative behavior of the two different calcareous sandswas compared to the siliceous sand. The results showed that particle shape played a key role in the behavior of soils in contractivephase. However, the shearing response of the used carbonate soils was more affected by particle crushing in dilation.
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Effect of Gradation Curve and Dry Density on Collapse Deformation Behavior of a Rockfill Material
Ahmadreza Tabibnejad,Ali Akbar Heshmati,Hossein Salehzadeh,Saeed Hashemi Tabatabaei 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.3
Rockfill material, such as other coarse grained materials, undergoes rapid or sudden settlements of relatively large values, withoutany changes in the applied loads and only because of submerging. In the literature this phenomenon is called collapse deformation. The effects of gradation curve and dry density on the collapse deformation behavior of a rockfill material were explored and thechanges in the strength and deformability parameters of this material caused by submerging were determined. Two large scale triaxialequipments with three different sample diameters of 20, 30 and 80 cm were employed and a set of dry-saturated tests wereconducted. Specimens with different gradation curves and various initial dry densities were tested. The results indicate that in all ofthe dry-saturated tests, sudden reductions in the shear strengths and volumes of the specimens were observed during the submergingprocess. The effects of material maximum particle size, fines content and initial dry density on the value of sudden shear strengthreduction, internal friction angle reduction caused by saturation (Δφc), the change in elasticity modulus of the material due tosubmerging, i.e., (Ewet/Edry), and also the saturation-induced sudden volumetric strain (εvc) were evaluated and discussed.
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Effect of Stress Conditions on Collapse Deformation Behavior of a Rockfill Material
Ali Akbar Heshmati,Ahmadreza Tabibnejad,Hossein Salehzadeh,Saeed Hashemi Tabatabaei 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.6
A set of saturated and dry-saturated large-scale triaxial tests were conducted in order to explore the effects of stress conditions on the saturation-induced collapse deformation behavior of a rockfill material. Specimens were tested in different confining pressures and for dry-saturated tests the specimens were submerged in various shear stress levels. The results indicate that in all of the drysaturated tests a sudden reduction in the volume of the specimens was observed during the submerging process. The ratio of the minimum axial strength of a submerged specimen (at the end of the saturation process) to the shear strength of the specimen before saturation is defined as the coefficient of stress recovery, Csr. Results of the dry-saturated tests showed that this ratio increases as the confining pressure increases and decreases by increasing the shear stress level. According to the results of dry-saturated tests the values of internal friction angle reduction caused by saturation (Δφc), the ratio of the elasticity modulus of the material after saturation to its elasticity modulus in dry condition, i.e., Ewet/Edry, and also the saturation induced sudden volumetric strain (εvc) decrease as the confining pressure increases. However the shear stress level does not have any meaningful effect on the variation of Dfc, Ewet/Edry and (εvc).
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S. Mohammad Shoari Shoar,Ali A. Heshmati R.,Hossein Salehzadeh 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.1
A series of centrifuge tests were performed to evaluate surcharge effects on the behavior of nailed vertical excavations. The primary purpose was to observe the mechanism of failure surface development and to compare the test results with software results based on equilibrium limit analysis. In this experiment, four different surcharges were applied to both samples with and without nails. Applying surcharge and the following excavation were performed in 40 g acceleration. At the beginning of the test, the excavation was maintained using a water-filled membrane, right next to it. At the target acceleration, the surcharge was modelled by filling the loading tank over the sample with water, and finally, with water draining from the membrane, soil excavation was simulated. Eventually, failure surfaces resulted from the experiment were compared with the ones calculated by the equilibrium limit analysis-based software. Results revealed that the shapes of failure surfaces are bilinear in all tests and that the surcharge has its effects on the development of failure surfaces. In the meantime, the pull-out mechanism was observed in the nails during failure, with no bending. The equilibrium limit analysis also estimates the width of failure wedge well and its depth conservatively.
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