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centrifuge-modeling
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Evaluation of variable permeability model in simulation of seismic behavior of uniform level and gently sloping sand layers
, Article Earth Sciences Research Journal ; Volume 24, Issue 3 , 2020 , Pages 328-336 ; Seyfi, S ; Shahir, H ; Sharif University of Technology
Universidad Nacional de Colombia
2020
Abstract
In this study, a fully coupled dynamic finite element model was employed for numerical simulation of the response of level to gently sloping saturated sand layers subjected to cyclic loading. This model utilized a critical state two-surface-plasticity constitutive model to simulate the cyclic behavior of sandy soil. Moreover, a recently proposed variable permeability function was implemented in the numerical model to reflect the effects of soil permeability variations during the liquefaction phenomenon. The numerical model was validated by simulating a number of well-documented geotechnical centrifuge tests with different relative density of sand, base acceleration time history, and surface...
Performance of elevated energy pile groups with different pile spacing in clay subjected to cyclic non-symmetrical thermal loading
, Article Renewable Energy ; Volume 172 , 2021 , Pages 998-1012 ; 09601481 (ISSN) ; Farivar, A ; Gomaa, S. M. M. H ; Shakeel, M ; Jafarzadeh, F ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
There is an increasing interest and use of energy foundation worldwide. Full-scale tests, physical model tests at one Earth's gravity and at elevated gravity in a geotechnical centrifuge and numerical simulations have been widely reported in the literature. Almost all studies have focused on single energy piles (EPs) and pile groups subjected to symmetrical thermal loads, although it is not unusual to have energy pile groups stressed by non-symmetrical thermal loads. In this study, a series of non-symmetrical thermal loading centrifuge model tests were conducted in saturated soft clay (OCR = 1.7), which is much vulnerable to temperature changes. The tests aim to investigate the effects of...
Thermal Cyclic Effects on the Long-Term Behaviour of Elevated Floating Energy Pile Groups in Saturated Lightly Overconsolidated Clay by Centrifuge Modelling
, Ph.D. Dissertation Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
There is an increasing interest and use of energy foundations worldwide. Heat transfer from/to energy piles may cause plastic contraction of soft clay with a low overconsolidation ratio (OCR) during heating and cooling. This can influence pile-soil interaction due to thermally induced excess pore water pressure and changes of lateral stress acting on the pile.These thermally induced phenomena cause additional plastic settlement of the soil and pile. The irreversible settlement may cause serviceability or even ultimate limit state problems for floating energy piles whose capacity is mainly derived from shaft resistance. Due to intended operational needs or by accident, cyclic non-symmetrical...
A new correlation on the MEXICO experiment using a 3D enhanced blade element momentum technique
, Article International Journal of Sustainable Energy ; Vol. 33, issue. 2 , 2014 , pp. 448-460 ; ISSN: 14786451 ; Jafari, A ; Schaffarczyk, A. P ; Keyhani, A ; Mahmoudi, J ; Sharif University of Technology
Abstract
The blade element momentum (BEM) theory is based on the actuator disc (AD) model, which is probably the oldest analytical tool for analysing rotor performance. The BEM codes have very short processing times and high reliability. The problems of the analytical codes are well known to the researchers: the impossibility of describing inside the one-dimensional code the three-dimensional (3D) radial flows along the span-wise direction. In this work, the authors show how the 3D centrifugal pumping affects the BEM calculations of a wind turbine rotor. Actually to ascertain the accuracy of the analytical codes, the results are compared with rotor performance, blade loads and particle image...
Validity of menard relation in dynamic compaction operations
, Article Proceedings of the Institution of Civil Engineers: Ground Improvement ; Volume 162, Issue 1 , 2009 , Pages 37-45 ; 17550750 (ISSN) ; Pak, A ; Shahir, H ; Sharif University of Technology
2009
Abstract
Dynamic compaction (DC) is a common soil improvement technique, used extensively worldwide. DC treatment design is usually based upon empirical relations and past experience. The common problem with all empirical relations is oversimplification of the mechanisms, and the use of parameters that are highly dependent on engineering judgement. In this paper, a developed finite-element code is used for modelling the impact behaviour of dry and moist sandy soil. The code is verified against the results of centrifuge tests. Then the validity of the popular Menard empirical relation for determination of improvement depth in DC design is investigated. The effect of initial relative density, tamper...