Papers by Somayeh Behraftar
Desiderata Geotechnica, 2019
The observation of structural changes inside geo-materials during testing is still uncommon in ge... more The observation of structural changes inside geo-materials during testing is still uncommon in geotechnical engineering. New developments in imaging techniques and improved analysis methods allow us for the first time to observe structural changes inside geo-materials and to provide us with the required information for developing new knowledge and constitutive relationships. The presented paper introduces three approaches for observing structural changes in porous media: (1) Particle Imaging Velocimetry (PIV) in combination with transparent hydro-gel beads, (2) Spatial Time Domain Reflectometry (Spatial TDR) for observing porosity distributions during contact erosion testing, and (3) Ultra High Speed Camera (UHSC) imaging in combination with a brittle, low strength rock like material for investigating hydraulic fracturing.
Rudarsko-geološko-naftni zbornik, 2021
One of the criteria in the operational efficiency of drilling is the rate of penetration of the d... more One of the criteria in the operational efficiency of drilling is the rate of penetration of the drill bit. Numerous factors affect the rate of penetration. Identification of the effective factors on rate of penetration may lead to a more accurate assessment of drilling time, and as a result, the controlling of operational costs. The concurrent effect of the entire influential factors as well as the differing significance of each of them on the rate of penetration makes the study and optimization of drilling operations much more complicated and difficult. Using the rock engineering systems (RES), the impact of effective operational and geomechanical factors on the rate of penetration has been assessed in this article and a model has been proposed for the prediction of the rate of penetration. Data from one of the wells within the Azadegan oilfield have been used in order to study the impact of effective factors on the rate of penetration. To this end, the effective factors on rate of...
In this study, a micro-mechanical model is developed to study the fracture propagation process in... more In this study, a micro-mechanical model is developed to study the fracture propagation process in rocks. The model is represented by an array of bonded particles simulated by the Discrete Sphero-Polyhedra Element Model (DSEM), which was introduced by the authors previously. It allows the modelling of particles of general shape, with no internal porosity. The DSEM method is used to model the Crack Chevron Notch Brazilian Disc (CCNBD) test suggested by the International Society of Rock Mechanics (ISRM) for determining the fracture toughness of rock specimens. CCNBD specimens with different crack inclination angles relative to the direction of loading are modelled to investigate the fracture geometry and propagation. The Crack Mouth Opening Displacement (CMOD) is calculated, and the results are validated using experimental results obtained from the literature. The motivation behind using this technique is the desire to study micro-mechanical aspects of fracture propagation in rocks and...
Applied Mechanics and Materials, 2016
The purpose of this paper is to investigate the fracture modes of the crack propagation of fourte... more The purpose of this paper is to investigate the fracture modes of the crack propagation of fourteen sandstone samples under Cracked Chevron Notch Brazilian Disc (CCNBD) test conditions through the use of image analysis and the high speed camera. The fracture mode is characterized by the displacement of 0.5mm glass beads placed on the sandstone surface relative to the approximate orientation of the fracture propagation. Using a Phantom v2011 High Speed Camera the fracture generation and propagation of the samples are recorded and processed for image analysis. ImageJ with Multi-Tracker and Manual Tracker, as well MATLAB® software were used to analyze the movement of particles during fracture propagation. It was found that the ImageJ software was able to track the movement of the particles and the output of the MATLAB® script was able to plot vector trajectories of the particles. For the analysis of samples tested under different orientations it was found that both shear mode and mixed...
Computers and Geotechnics, 2017
Journal of the Geological Society of India, 2017
Accidents in underground collieries, under geological and geotechnical uncertainties, cause some ... more Accidents in underground collieries, under geological and geotechnical uncertainties, cause some irrecoverable consequences for workers. Recognizing and studying the effective factors in the occurrence of such accidents have a very crucial impact on improving worker safety and reducing mining costs. This paper introduces a new and beneficial technique named "modified risk priority number (MRPN)" for recognizing and assessing those risks which may cause working accidents in Iranian underground collieries. The available qualitative data from the mines was quantified using standard tables established for risk assessment. The technique was exemplified using data from mine accidents in Kerman and East-Alborz regions. Roof-fall was found to be the most significant risk factor in the mines that were investigated.
Applied Mechanics and Materials, 2016
In this study, a micro-mechanical model is developed to study the correlation of the point load i... more In this study, a micro-mechanical model is developed to study the correlation of the point load index in rocks with uniaxial compressive strength (UCS) tests. The model is represented by an array of bonded particles simulated by a novel discrete based model, which was introduced by the authors previously. The point load test (PLT) is performed in the field on rock samples to classify and estimate the UCS of a rock type via the index-to-strength correlation factor k. Numerical analyses, such as the one presented in this work, will serve to close the knowledge gap concerning the correlation between k, UCS and other material properties of rocks.
Computer Methods and Recent Advances in Geomechanics, 2014
ABSTRACT In this paper, a novel Discrete Element and Lattice Boltzmann Method for the study of th... more ABSTRACT In this paper, a novel Discrete Element and Lattice Boltzmann Method for the study of the hydraulic fracturing is presented. The solid phase is simulated by the Discrete Element Method combined with a bonding model to represent fracture and damage phenomena. The solid phase interacts with the fracturing fluid simulated by the Lattice Boltzmann Method. The domain is built from a triangular mesh where each element is transformed into a discrete particle except for a hole in the middle representing the injection point. The fluid pressure is gradually increased until the fracture starts and its evolution is closely monitored. Characteristics of the process are produced such as: A tensile initiation of the fracture followed by a mixed mode propagation; a breaking point of the fluid pressure approximately equal to the tensile strength plus the minimum stress that the sample is subjected to; and that the propagation path mostly follows the maximum stress. In the paper it is explained how the model can be further validated and how the parameters could be obtained from real measurements. It is expected that a fully validated version of this model will have immediate impact on both fundamental and applied research on the hydraulic fracturing process.
Computers and Geotechnics, 2017
A micro-mechanical model is developed to study the fracture propagation process in rocks. The mod... more A micro-mechanical model is developed to study the fracture propagation process in rocks. The model is represented by an array of bonded particles simulated by the discrete based method. Experimental results of tests using Cracked Chevron Notched Brazilian Discs (CCNBD) with different inclination angles relative to the direction of loading are used to calibrate and validate the model. Dimensional analysis is used to identify and minimise the microscale parameters to be considered. The comparison between experimental and computational results shows a satisfactorily good agreement.
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Papers by Somayeh Behraftar