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A new approach for group efficiency of drilled shafts in sand subjected to axial loading
, Article International Journal of Geotechnical Engineering ; 2016 , Pages 1-13 ; 19386362 (ISSN) ; Mahvelati, S ; Sharif University of Technology
Taylor and Francis Ltd
2016
Abstract
Understanding pile group behaviour is a critical key for geotechnical engineers. Nevertheless, there have been inadequate studies in the literature which tackle the many aspects of this important type of foundation. In this paper, a new and simple approach is presented for estimating group efficiency of drilled shafts installed in sandy soil under axial loading. This approach may prove handy for geotechnical practitioners in their pile group design decisions. The distinguishing point about this approach is its being less-conservative in comparison with the rather few previous equations available in the literature. The mathematical approach derived in this study is based on results from...
A new approach for group efficiency of drilled shafts in sand subjected to axial loading
, Article International Journal of Geotechnical Engineering ; Volume 12, Issue 2 , 2018 , Pages 172-184 ; 19386362 (ISSN) ; Mahvelati, S ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
Understanding pile group behaviour is a critical key for geotechnical engineers. Nevertheless, there have been inadequate studies in the literature which tackle the many aspects of this important type of foundation. In this paper, a new and simple approach is presented for estimating group efficiency of drilled shafts installed in sandy soil under axial loading. This approach may prove handy for geotechnical practitioners in their pile group design decisions. The distinguishing point about this approach is its being less-conservative in comparison with the rather few previous equations available in the literature. The mathematical approach derived in this study is based on results from...
Effect of kerosene contamination on the physical and mechanical properties of sandy soil
, Article Innovative Infrastructure Solutions ; Volume 4, Issue 1 , 2019 ; 23644176 (ISSN) ; Zohrevand, P ; Rezaee, M ; Sharif University of Technology
Springer
2019
Abstract
Oil contamination can affect the mechanical and physical properties of soil, making its reuse a challenge. In the present study, the effect of kerosene contamination on two types of poorly graded sand (S1 and S2) was investigated. Geotechnical tests for compaction, direct shear and constant head permeability were conducted. The compaction test revealed that dry density increased at a 3% and 6% kerosene content for S1 and S2 soil, respectively. A further increase in kerosene content caused the dry density to decrease for both S1 and S2. The optimum moisture content of kerosene-contaminated soil samples decreased. The direct shear test showed that kerosene contamination increased cohesion and...
A numerical approach on side resistance of drilled shafts embedded in sandy soils
, Article International Journal of Geotechnical Engineering ; 2019 ; 19386362 (ISSN) ; Ahmadi, M. M ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
This study numerically investigates the side resistance of drilled shafts (bored piles) in sand using FLAC2D computer program. The results of the equations available in the literature are compared with the results of the present numerical study. A series of analyses is also conducted to assess the effects of various soil and pile parameters on the magnitude of side resistance of bored piles embedded in sand. Furthermore, the coupling (combined) effect of coefficient of lateral earth pressure with friction angle, and the coefficient of lateral earth pressure with a unit weight of soil on side resistance are investigated. The results show that the maximum effect of K0 on side resistance occurs...
A numerical approach on side resistance of drilled shafts embedded in sandy soils
, Article International Journal of Geotechnical Engineering ; 2019 ; 19386362 (ISSN) ; Ahmadi, M. M ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
This study numerically investigates the side resistance of drilled shafts (bored piles) in sand using FLAC2D computer program. The results of the equations available in the literature are compared with the results of the present numerical study. A series of analyses is also conducted to assess the effects of various soil and pile parameters on the magnitude of side resistance of bored piles embedded in sand. Furthermore, the coupling (combined) effect of coefficient of lateral earth pressure with friction angle, and the coefficient of lateral earth pressure with a unit weight of soil on side resistance are investigated. The results show that the maximum effect of K0 on side resistance occurs...
Drilled shafts in sand: failure pattern and tip resistance using numerical and analytical approaches
, Article International Journal of Geotechnical Engineering ; 2021 ; 19386362 (ISSN) ; Ahmadi, M. M ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
Drilled shafts are one of the most important types of pile foundations. Several researchers have suggested different soil failure patterns for driven piles; however, for drilled shafts, this issue is inadequately addressed in the literature. In this paper, a numerical approach was pursued to obtain the location and dimensions of plastic zones around the tip of drilled shafts. The dependence of the suggested failure pattern size on the soil properties and drilled shaft dimensions was investigated. Based on several analyses, a soil jug-shaped failure pattern around the tip of drilled shafts was proposed, and its dimensions were determined using the regression-based and trial and error...
Risk analysis of liquefaction potential in South West Tehran
, Article Amirkabir (Journal of Science and Technology) ; Volume 15, Issue 58 D , 2004 , Pages 521-534 ; 10150951 (ISSN) ; Haeri, S. M ; Shirazi, A ; Olyaei, M. N ; Bakhshi, A ; Sharif University of Technology
2004
Cone penetration test in sand: anumerical-analytical approach
, Article Computers and Geotechnics ; Volume 90 , 2017 , Pages 176-189 ; 0266352X (ISSN) ; Golestani Dariani, A. A ; Sharif University of Technology
Abstract
Separation of the effects of initial horizontal stress and relative density on cone tip resistance in sandy soils has been a complicated issue for many years. In order to overcome this problem, a numerical modeling of CPT which has been verified by calibration chamber tests, has been used in this paper to achieve a reliable analytical solution. The analytical solution has resulted in two relationships for sleeve friction and cone tip resistance in terms of the initial conditions of sandy soil. Based on the presented solution, the initial horizontal stress and relative density can be determined according to CPT measurements. © 2017 Elsevier Ltd
Numerical modeling of piles in sandy soils considering stress dependent modulus of elasticity
, Article Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014, 22 September 2014 through 25 September 2014, Kyoto ; 2015 , Pages 973-977 ; 9781138001480 (ISBN) ; Abadi, S. M ; Sharif University of Technology
Taylor and Francis - Balkema
2015
Abstract
Pile Foundations are used to transfer loads from superstructures to the underlying competent soil layers. Predicting pile bearing capacity is among the most interesting subjects for geotechnical engineers. In this study, a single pile is modeled in axisymmetric condition. The soil is considered to be a sandy soil. Then, results of the model were verified with a full scale pile load test performed by previous researchers. In order to take into consideration the real behavior of sandy soils, a variation of modulus of elasticity with respect to the changes in the mean effective stress was taken into account. The dependency of soil modulus to the mean effective stress makes the model more...
In situ horizontal stress from CPT in sand: a new approach
, Article International Journal of Geotechnical Engineering ; Volume 13, Issue 6 , 2019 , Pages 538-547 ; 19386362 (ISSN) ; Golestani Dariani, A. A ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
Despite the various approaches in the literature adopted for analysing cone penetration test (CPT), determination of the initial horizontal stress and relative density of a sandy soil during this test has not been tackled yet. In order to propose a new method in this regard, a numerical study of CPT has been performed and the predicted results have been compared with several databases of comprehensive calibration chamber tests. The penetration mechanism has been then fully investigated by presenting different kinds of outputs for the surrounding soil. Finally, an innovative procedure has been suggested for estimating the initial horizontal stress and relative density during performing CPT in...
In situ horizontal stress from CPT in sand: a new approach
, Article International Journal of Geotechnical Engineering ; Volume 13, Issue 6 , 2019 , Pages 538-547 ; 19386362 (ISSN) ; Golestani Dariani, A. A ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
Despite the various approaches in the literature adopted for analysing cone penetration test (CPT), determination of the initial horizontal stress and relative density of a sandy soil during this test has not been tackled yet. In order to propose a new method in this regard, a numerical study of CPT has been performed and the predicted results have been compared with several databases of comprehensive calibration chamber tests. The penetration mechanism has been then fully investigated by presenting different kinds of outputs for the surrounding soil. Finally, an innovative procedure has been suggested for estimating the initial horizontal stress and relative density during performing CPT in...
Application of a bond model for constitutive modeling of cemented gravely sands
, Article 12th International Conference on Computer Methods and Advances in Geomechanics 2008, Goa, 1 October 2008 through 6 October 2008 ; Volume 1 , October , 2008 , Pages 732-738 ; 9781622761760 (ISBN) ; Haeri, S. M ; National Institute of Disaster Management (NIDM); American Society of Civil Engineers (ASCE) ; Sharif University of Technology
2008
Abstract
In this paper the framework for a constitutive model which is developed for a cemented gravely sand is presented. The model is based on separation technic namely the separation of the behavior to the uncemented soil and the cemented bonds. They are combined in a manner to satisfy the deformation consistency and energy equilibrium equations. The uncemented soil behavior is modeled using a modified model originally proposed by Pastor et al. (1985) for sandy soils. Also, based on the results of the experiments, a new model for the bonds is developed. Combination of these two parts results in the modeling of the behavior of cemented gravely soils in drained and undrained states
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...
A numerical approach on side resistance of drilled shafts embedded in sandy soils
, Article International Journal of Geotechnical Engineering ; Volume 14, Issue 6 , 2020 , Pages 644-652 ; Ahmadi, M. M ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
This study numerically investigates the side resistance of drilled shafts (bored piles) in sand using FLAC2D computer program. The results of the equations available in the literature are compared with the results of the present numerical study. A series of analyses is also conducted to assess the effects of various soil and pile parameters on the magnitude of side resistance of bored piles embedded in sand. Furthermore, the coupling (combined) effect of coefficient of lateral earth pressure with friction angle, and the coefficient of lateral earth pressure with a unit weight of soil on side resistance are investigated. The results show that the maximum effect of K0 on side resistance occurs...
Study of pore pressure variation during liquefaction using two constitutive models for sand
, Article Soil Dynamics and Earthquake Engineering ; Volume 27, Issue 1 , 2007 , Pages 60-72 ; 02677261 (ISSN) ; Shahir, H ; Pak, A ; Sharif University of Technology
2007
Abstract
Numerical analyses of liquefiable sand are presented in this paper. Liquefaction phenomenon is an undrained response of saturated sandy soils when they are subjected to static or dynamic loads. A fully coupled dynamic computer code is developed to predict the liquefaction potential of a saturated sandy layer. Coupled dynamic field equations of extended Biot's theory with u-P formulation are used to determine the responses of pore fluid and soil skeleton. Generalized Newmark method is employed for integration in time. The soil behavior is modelled by two constitutive models; a critical state two-surface plasticity model, and a densification model. A class 'B' analysis of a centrifuge...
Integrated numerical study of rainfall-induced landslides from initiation to propagation using saturation-based rheological model
, Article Scientia Iranica ; Volume 29, Issue 5 B , 2022 , Pages 2304-2316 ; 10263098 (ISSN) ; Manzari, M. T ; Hajilouy Benisi, A ; Sharif University of Technology
Sharif University of Technology
2022
Abstract
This paper presents an integrated two-dimensional numerical framework for simulating rainfall-induced landslides from instability initiation to post-failure flow. To describe the entire process, three steps are considered in this study: (1) a coupled hydrostability analysis which detects the failure plane using the Finite Element Method (FEM) (pre-failure stage); (2) computing the local rheology of the failed mass (wet sandy soil) based on the water saturation at the onset of failure using the saturation-based rheological model (transition stage); and (3) a continuum-based propagation analysis which solves the flow of the wet material employing the Smoothed Particle Hydrodynamics (SPH)...
Drilled shafts in sand: failure pattern and tip resistance using numerical and analytical approaches
, Article International Journal of Geotechnical Engineering ; Volume 16, Issue 8 , 2022 , Pages 974-990 ; 19386362 (ISSN) ; Ahmadi, M. M ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
Drilled shafts are one of the most important types of pile foundations. Several researchers have suggested different soil failure patterns for driven piles; however, for drilled shafts, this issue is inadequately addressed in the literature. In this paper, a numerical approach was pursued to obtain the location and dimensions of plastic zones around the tip of drilled shafts. The dependence of the suggested failure pattern size on the soil properties and drilled shaft dimensions was investigated. Based on several analyses, a soil jug-shaped failure pattern around the tip of drilled shafts was proposed, and its dimensions were determined using the regression-based and trial and error...
Dynamic impedance functions of machine foundations on sandy soils by physical model tests
, Article Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering: The Academia and Practice of Geotechnical Engineering, 5 October 2009 through 9 October 2009, Alexandria ; Volume 1 , 2009 , Pages 478-481 ; 9781607500315 (ISBN) ; Mashhadi, H. G ; Sharif University of Technology
Abstract
In order to improve new methods of design of machine foundations by means of impedance function, implementation of experimental investigations to calibrate these methods is vital. The physical model tests were carried out in a steel container with dimension of 1×1×0.9 m. The Babolsar sand was employed in the model. To eliminate reflection of elastic waves, a sawdust layer was used in the lateral walls and bottom of the container. Also, in order to have homogeneous medium with unified density, air pluviation of sand method was employed. Response of the models to harmonic excitations was measured using various instruments deployed around the foundation. Results of the tests are shown in the...
Numerical-probabilistic modeling of the liquefaction-induced free fields settlement
, Article Soil Dynamics and Earthquake Engineering ; Volume 149 , 2021 ; 02677261 (ISSN) ; Pak, A ; Pakzad, A ; Ayoubi, P ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Liquefaction is a phenomenon through which saturated sandy soil loses its shear strength and turns into a liquefied state. One of the most detrimental consequences of liquefaction is the reconsolidation volumetric settlements after the earthquakes, which is due to the dissipation of excess pore pressure caused by earthquakes. Severe floods can follow these settlements in free fields such as grounds close to the sea or rivers. Several researchers studied this phenomenon using data obtained from experiments in the lab or observations in the fields. Previous works were mainly based on a limited number of experimental observations and considered loadings and boundary conditions that were...
Characterizing the effect of fines content on the small strain shear modulus of sand-silt mixtures during hydraulic hysteresis
, Article 4th International Conference on Transportation Geotechnics, ICTG 2021, 23 May 2021 through 26 May 2021 ; Volume 165 , 2022 , Pages 837-849 ; 23662557 (ISSN); 9783030772338 (ISBN) ; Mohsen Haeri, S ; Khosravi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Small strain shear modulus, Gmax, is one of the most important parameters for the characterization of the behavior of earth structures subjected to static or dynamic loading conditions. This research presents an experimental laboratory study on the effect of non-plastic fines content and hydraulic hysteresis on the Gmax of unsaturated sandy soils. In this regard, clean Firoozkuh No. 161 silica sand which is classified as poorly graded sand was mixed with different percentages of non-plastic Firoozkuh silt. A set of bender element tests were carried out using two modified triaxial devices. The modifications on these two apparatus were to add HAV ceramic discs for air–water control of...