Search for: degree-of-saturations
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    Coupled effects of suction and degree of saturation on large strain shear modulus of unsaturated sands

    , Article Unsaturated Soils: Research and Applications - Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 ; Vol. 2, issue , July , 2014 , p. 1559-1564 ; 978-1-138-00150-3 Jafarzadeh, F ; Ahmadinezhad, A ; Sadeghi, H ; Sharif University of Technology
    Predictions of soil behavior in response to dynamic loads require an understanding of dynamic properties of soil. Studies on dynamic properties of unsaturated soils at large-strains are quite limited, while some dynamic loadings, like earthquakes, are in the medium to large-strain ranges. A cyclic simple shear apparatus was developed to measure large-strain shear modulus and damping ratio under different matric suction or degree of saturation. Six cyclic tests, with referring to the soil-water retention curve, were conducted on clean medium sand. Results indicated that shear modulus slightly increases when suction varies from zero up to the air entry value. Approaching the residual value, a... 

    A semi-empirical shear strength model for infilled rock fractures with infills in an unsaturated state

    , Article Geotechnical Frontiers 2017, 12 March 2017 through 15 March 2017 ; Issue GSP 280 , 2017 , Pages 529-538 ; 08950563 (ISSN) Khosravi, A ; Mousavi, S ; Khosravi, M ; Brandon T. L ; Valentine R. J ; Geo-Institute (G-I) of the American Society of Civil Engineers; Industrial Fabrics Association International (IFAI) ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2017
    Based on the results of recent studies, comprehensive characterization of the behavior of infilled rock fractures under saturated and unsaturated conditions requires knowledge of morphological details of fracture surface, as well as state of stress of infill materials and their initial innate conditions (e.g., void ratio, water content, degree of saturation and dry density). This paper describes a semi-empirical equation to interpret the effects of wall-roughed nature of the fractures and presence of partially saturated fine materials within the fractures on the behavior of infilled rock fractures during shear. The proposed equation incorporates the soil-water retention curve parameters as... 

    The hydro-mechanical behavior of infilled rock joints with fill materials in unsaturated conditions

    , Article Geotechnical Special Publication ; Issue 231 , 3-7 March , 2013 , Pages 129-138 ; 08950563 (ISSN) ; 9780784412787 (ISBN) Khosravi, A ; Khosravi, M ; Meehan, C. L ; Sharif University of Technology
    The existence, nature, and frequency of discontinuities in a given rock mass typically govern the overall shear behavior of the rock. The presence of fine materials such as clay and silt within rock joints, whether the product of infilling or natural weathering processes, can have a significant effect on the shear behavior of the rock joint. When assessing the strength of filled rock joints, it is therefore necessary to determine the separate strengths of both the rock and the joint infill material, and to also have a good understanding of the interaction between the two for various joint geometries and levels of infilling. Much of the existing research on the shear strength of filled rock... 

    Hardening behavior of a hydro collapsible loessial soil

    , Article 15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015, 9 November 2015 through 13 November 2015 ; September , 2015 , Pages 253-257 Haeri, S. M ; Garakani, A. A ; Association for Disaster Prevention Research; et al.; Fukuoka Convention and Visitors Bureau; Japan Society for the Promotion of Science - Grant-in-Aid for Publication of Scientific Research Results; Kyushu Regional Planning Association; The Maeda Engineering Foundation ; Sharif University of Technology
    Asian Regional Conference on Soil Mechanics and Geotechnical Engineering  2015
    Hydro collapsible soils are of kinds of problematic soils which show high shear strength at low degrees of saturation but due to wetting, their Meta stable structure collapses and will be subjected to large deformation. In this study by applying isotropic triaxial loadings to undisturbed samples, mechanical behavior of a highly collapsible loessial soil has been assessed. During tests, matric suction of the samples was controlled as well as the mean net stress, and the variation of the degree of saturation was monitored continuously. Two types of stress paths were conducted on the samples namely "Isotropic induced collapse" under applying constant matric suctions and "wetting induced... 

    Suction-induced hardening effects on the shear modulus of unsaturated silt

    , Article International Journal of Geomechanics ; Volume 16, Issue 6 , 2016 ; 15323641 (ISSN) Khosravi, A ; Salam, S ; McCartney, J. S ; Dadashi, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE) 
    The small-strain shear modulus Gmax is a key material parameter in modeling the behavior of soils subjected to dynamic loading. Recent experimental results indicate that seasonal weather interaction with near-surface soils causes Gmax to change by up to an order of magnitude in some climates, with a hysteretic response upon drying and wetting. The increase in Gmax during drying and the stiffer response during subsequent wetting have been postulated to be due to plastic hardening during drying. To further understand this behavior, a series of isotropic compression tests were performed on compacted silt specimens at different values of matric suction to evaluate changes in the preconsolidation... 

    Effects of initial suction and degree of saturation on dynamic properties of sand at large strain

    , Article Scientia Iranica ; Volume 28, Issue 1 , 2021 , Pages 156-174 ; 10263098 (ISSN) Jafarzadeh, F ; Ahmadinezhad, A ; Sadeghi, H ; Sharif University of Technology
    Sharif University of Technology  2021
    Soil deposits may experience different hydraulic states in terms of suction (φ) and saturation degree (Sr) while being subjected to large strain caused by dynamic loading during earthquakes. This phenomenon was investigated by considering the effects of initial φ, initial (Sr, sample preparation method, drainage condition, and cycle number (N) on dynamic properties. Shear modulus (G) and damping ratio (D) were specifically studied for unsaturated sand using a modified cyclic simple shear device for all zones of Soil Water Retention Curve (SWRC). Results revealed the relative significance of both φ and Sr in relation to SWRC on observed trends in G and D. Based on the analysis of some results... 

    Experimental study on dynamic properties of sand with emphasis on the degree of saturation

    , Article Soil Dynamics and Earthquake Engineering ; Volume 32, Issue 1 , 2012 , Pages 26-41 ; 02677261 (ISSN) Jafarzadeh, F ; Sadeghi, H ; Sharif University of Technology
    Cyclic drained and undrained tests were performed in a modified simple shear device in order to specifically investigate the effect of saturation ratio on shear modulus and damping parameters of sand. In addition to the degree of saturation, the effects of number of cycles, vertical consolidation stress, shear strain amplitude and relative density on dynamic properties of sand were investigated. Dynamic stiffness and damping characteristic were found to be substantially independent of saturation ratio in the range of 25-75%. However, by approaching the full saturation state, the values of modulus fall sharply and damping of loose samples increases dramatically from corresponding values of... 

    Dynamic parameters of saturated and unsaturated sand at different ranges of shear strain levels in cyclic simple shear tests

    , Article 14th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering ; 2011 Jafarzadeh, F ; Golshan, Z ; Sharif University of Technology
    In order to evaluate dynamic properties of Babolsar and Toyoura sands at saturation levels of 25, 50, 75 & 100%, a series of cyclic simple shear tests were carried out. The SGI type cyclic simple shear device was used to study the shear modulus, G, and damping ratio, D, of the above mentioned sands at cyclic shear strain of 0.5, 5 & 10%. The effect of degree of saturation (S), vertical consolidation stress (σ vc) and number of loading cycles (N) were investigated. On the basis of the tests results, the shear modulus approximately remains constant by change of degree of saturation from 25 to 50% and decreases when reaches the degree of saturation 75%. Damping ratio approximately is constant... 

    A shortest path problem in an urban transportation network based on driver perceived travel time

    , Article Scientia Iranica ; Volume 17, Issue 4 A , August , 2010 , Pages 285-296 ; 10263098 (ISSN) Ramazani, H ; Shafahi, Y ; Seyedabrishami, S. E ; Sharif University of Technology
    This paper proposes a method to solve shortest path problems in route choice processes when each link's travel time is a fuzzy number, called the Perceived Travel Time (PTT). The PTT is a subjective travel time perceived by a driver. The algorithm solves the fuzzy shortest path problem (FSPA) for drivers in the presence of uncertainty regarding route travel time. For congested networks, the method is able to find the shortest path in terms of perceived travel time and degree of saturation (congestion) along routes at the same time. The FSPA can be used to support the fuzzification of traffic assignment algorithms. The applicability of the resulting FSPA for the traffic assignment was tested... 

    Seismic behavior of pile-supported systems in unsaturated sand

    , Article Soil Dynamics and Earthquake Engineering ; Volume 112 , 2018 , Pages 162-173 ; 02677261 (ISSN) Ghayoomi, M ; Ghadirianniari, S ; Khosravi, A ; Mirshekari, M ; Sharif University of Technology
    The seismic behavior of pile-supported systems has been an active area of research over the past decades. However, focus has mostly been on evaluating the seismic response of structures embedded in either dry or fully saturated soil conditions. In this study, series of dynamic centrifuge tests were conducted to investigate the effects of soil's degree of saturation on the seismic behavior of pile-supported superstructures. The scaled physical model tests were carried out on two distinct pile-mass systems embedded in uniform sand layers. A steady state infiltration technique was used to control matric suction profiles in the sand layer prior to shaking. The obtained results from these...