Papers by Abolfazl Abdollahipour
Journal of Mining and Environment, 2021
Determination of the optimum soil conditioning parameters in the earth pressure balance-tunnel bo... more Determination of the optimum soil conditioning parameters in the earth pressure balance-tunnel boring machines (EPB-TBMs) plays an important role in reaching an optimum thrust force and advance speed. Silty-clay (CL-ML) in line 1 of the Ahwaz metro project is used in order to find the conditioning parameters of slumps with different water contents and foam agents. The results obtained are a quantitative comparison between the parameters with different soil conditioning and water contents. Hence, the test results can be used to determine the most economical and technical conditioning parameters for a special condition of soil. The optimum quantity of foam expansion ratio (FER), foam injection ratio (FIR), percent ratio between the surfactant agent and the water volume (Cf), and cost for foam in this soil (based on the soil conditioning production cost) are 10, 157%, 2.07, 248 units, respectively. Soil conditioning with the optimum parameters obtained are tested in a TBM in two stages...
Journal of rock mechanics and geotechnical engineering, Mar 1, 2023
Construction and Building Materials
Environmental Earth Sciences
Acta Geophysica, 2021
Accurate gridded precipitation data with high spatial and temporal scales are required for divers... more Accurate gridded precipitation data with high spatial and temporal scales are required for diverse studies such as climatology, meteorology, and hydrology. Currently, one of the sources of global precipitation estimation is the satellite-based precipitation estimate products. Nonetheless, their spatial resolution is often too coarse for usage in local region and basin scales or for parameterizing of meteorological and hydrological models at regional scales. In the present paper, a reconstruction method of satellite-based monthly precipitation was developed to attain improved pixel-based precipitation data with high spatial resolution on Golestan province in Northern Iran. In this endeavor, we considered the spatially heterogeneous relationships between tropical rainfall measuring mission (TRMM) precipitation and environmental variables utilizing the moving-window regression methods, the geographically weighted regression (GWR) and the mixed geographically weighted regression (MGWR) ...
In order to measure precipitation as the main variable for estimating the runoff and designing hy... more In order to measure precipitation as the main variable for estimating the runoff and designing hydraulic structures, the satellite algorithm products that have the proper spatial and temporal coverage, can be used. In this study, at first, the daily streamflow simulation of Sarough-Cahy River from the Zarinehroud basin was conducted through the artificial neural network (ANN) and ground data of daily precipitation, temperature and discharge for the years of 1988 to 2008. The developed network was trained, validated and tested. Then, in order to evaluate the products of satellite precipitation algorithms in streamflow simulation which is the aim of this study, daily satellite rainfall data of PERSIANN, TMPA-3B42V7, TMPA-3B42RT and CMORPH between 2003 and 2008 were used as an input data to the trained ANN model. Considering indices of R2, RMSE and MAE implemented for evaluations, the results indicated that satellite rainfall algorithms are able to simulate runoff efficiently over the ...
Applied Thermal Engineering, 2021
Abstract Nowadays, waste heat recovery and refrigeration are leading energy challenges. For the g... more Abstract Nowadays, waste heat recovery and refrigeration are leading energy challenges. For the generation of additional power and refrigeration purposes, many systems were used. Among these systems, a modern electrochemical cycle based on the temperature dependence of the electrodes called thermally regenerative electrochemical cycle (TREC) was considered widely for converting heat to electricity and refrigeration. These systems have a high-temperature coefficient, which is an advantage over thermoelectric systems, high efficiency, low weight and volume, silent operation, sustainably generating power, no moving parts such as compressors, non-use of vulnerable refrigerants for environmental and clean technology, and ability to couple to various energy technologies to increase the energy efficiency of these systems. Also, an enormous amount of low-grade heat exists around us in energy technologies, such as photovoltaic technology, solar/geothermal heat, the waste heat of fuel cells, industry section and conversion and recovery of this low-grade heat is crucial. Therefore, reviewing the current state-of-the-art research and the progress on the thermally regenerative electrochemical systems for power generation and refrigeration focusing on the new material and design mechanism is essential. First, the principle of power generation cycle, TREC, and the refrigeration cycle, thermally regenerative electrochemical refrigeration (TRER), were utterly discussed for a better understanding of the cycles. Furthermore, the continuous system for these cycles was introduced for continuous power generation and refrigeration. Forasmuch as theoretical studies form the basis of experimental works, the power generation and refrigeration applications of these cycles were divided into theoretical and experimental studies. A literature review revealed that theoretical studies on both the TREC and TRER cycles are comprehensive, paving the way for experimental studies. In experimental studies, useful studies have been performed on power generation by this cycle and its continuous form system. However, despite the high potential of refrigeration cycle, very few studies have been done in this regard. Finally, some recommendations for future studies were made.
Journal of Water and Climate Change, 2020
In recent years, gridded precipitation data derived from satellite rainfall products have become ... more In recent years, gridded precipitation data derived from satellite rainfall products have become critical data sources for hydrological applications, especially in ungauged basins where rain gauges are sparse or nonexistent. Also, in streamflow simulations, since the existing rainfall–runoff modelling methods require exogenous input with some assumptions, neural networks can be an efficient solution. In this paper, to simulate daily streamflow on the Ghare Ghieh River basin in northwestern Iran, the Levenberg–Marquardt Neural Network (LMNN) and the Particle Swarm Optimization Neural Network (PSONN) models are proposed. These models are trained and tested with different input patterns from ground-based data for water years of 1988–2008. Then, three satellite-based precipitation datasets, including TRMM-3B42V7, TRMM-3B42RT, and PERSIANN with 0.25° × 0.25° resolutions from 2003 to 2008, are used as inputs for the best-trained models which were selected in the testing step. These produc...
Journal of Mining and Environment, Apr 1, 2021
A wellbore is a hole that is drilled to aid in the exploration and recovery of natural resources ... more A wellbore is a hole that is drilled to aid in the exploration and recovery of natural resources including oil and gas. Occasionally, in order to increase productivity index and porosity of the wellbore and reservoir, the well stimulation methods have been used. Hydraulic fracturing is one of these methods. Moreover, several explosions at the end of the well can stimulate the reservoir and create fractures around it. In this study, crack initiation in rock around the wellbore has been numerically modeled due to explosion. One, two, three, and four pairs of explosion have been set at the end of the wellbore on its wall. After each stage of the explosion, results have been presented and discussed. Results show that this method can initiate and probably propagate several fractures around the wellbore.
Rock Mechanics and Rock Engineering: From the Past to the Future, 2016
\textcopyright} 2016 Taylor {\&} Francis Group, London. Hydraulic fracturing (HF) stimula... more \textcopyright} 2016 Taylor {\&} Francis Group, London. Hydraulic fracturing (HF) stimulation of oil wells have made possible the current flourishing oil production from pay zones. Longer initial fractures length and shorter spacing increases oil production. However, these operations usually are expensive and may even cause interference and subsequent reduction in oil production. Analytical models do not consider fracture interference and assume equal fracture half-lengths. Therefore, optimizing initial fractures geometry using numerical methods is of high importance in a successful HF operation.Various geometrical parameters of initial HF cracks including patterns, spacings and crack lengths have been modeled using a higher order displacement discontinuity method (HODDM) in a horizontal oil well. Some of the most encountered problems in HF processes such as fracture interference and fracture arrest have been detected through numerical simulations. Considering several different loading cases, most suitable crack geometrical parameters have been obtained. The results are also confirmed by in-situ measurements available in the literature.
Journal of Mining and Environment, 2019
The explosion process of explosives in a borehole applies a very high pressure on its surrounding... more The explosion process of explosives in a borehole applies a very high pressure on its surrounding rock media. This process can initiate and propagate rock fractures, and finally, may result in the rock fragmentation. Rock fragmentation is mainly caused by the propagation of inherent pre-existing fractures of the rock mass and also from the extension of the newly formed cracks within the intact rock due to the explosion. In this work, the process of extension of blast-induced fractures in rock masses is simulated using the discrete element method. It should be noted that, in this work, fracture propagation from both the rock mass inherent fractures and newly induced cracks are considered. The rock mass inherent fractures are generated using the discrete fracture network technique. In order to provide the possibility of fracture extension in the intact rock blocks, they are divided into secondary blocks using the Voronoi tessellation technique. When the modeling is completed, the frac...
Journal of Mining and Environment, 2020
Determination of the borehole and fracture initiation positions is the main aim of a borehole sta... more Determination of the borehole and fracture initiation positions is the main aim of a borehole stability analysis. A wellbore trajectory optimization with the help of the mud pressure may be unreasonable since the mud pressure can only reflect the degree of difficulty for the initial damage to occur at the wellbore rather than the extent of the wellbore damage. In this work, we investigate the failure extension in different arbitrary inclination boreholes under different in-situ stress regimes. Assuming the plane strain condition, the Mohr-Coulomb, Mogi-Coulomb, and Modified Lade rock failure criteria are utilized. We present an analytical equation to determine the optimum drilling trajectory of an Iranian oilfield. In order to predict the degree of wellbore damage, the initial shear failure location, failure width, and failure depth of arbitrary wellbores are determined. Then a new model is derived to calculate the initial failure area of a directional wellbore because it is more ef...
Journal of Mining and Environment, 2018
The permeability and coupled behavior of pore pressure and deformations play an important role in... more The permeability and coupled behavior of pore pressure and deformations play an important role in hydraulic fracturing (HF) modeling. In this work, a poroelastic displacement discontinuity method is used to study the permeability effect on the HF development in various formation permeabilities. The numerical method is verified by the existing analytical and experimental data. Then the propagation of a hydraulic fracture in a formation with a range of permeabilities is studied. The time required for propagation of an HF to 10 times its initial length is used to compare the propagation velocity in the formations with different permeabilities. The results obtained show that the HF propagation can be significantly delayed by a permeability less than almost 10-9 D. Also the effect of HF spacing on the propagation path is studied. It was shown that the stress shadowing effect of HFs remained for a longer spacing than in the elastic model due to the required time for fluid leak-off in the ...
A fourth order formulation of the displacement discontinuity method (DDM) is proposed for the cra... more A fourth order formulation of the displacement discontinuity method (DDM) is proposed for the crack analysis of brittle solids such as rocks, glasses, concretes and ceramics. A fourth order boundary collocation scheme is used for the discretization of each boundary element (the source element). In this approach, the source boundary element is divided into five sub-elements each recognized by a central node where the displacement discontinuity components are to be numerically evaluated. Three different formulating procedures are presented and their corresponding discretization schemes are discussed. A new discretization scheme is also proposed to use the fourth order formulation for the special crack tip elements which may be used to increase the accuracy of the stress and displacement fields near the crack ends. Therefore, these new crack tips discretizing schemes are also improved by using the proposed fourth order displacement discontinuity formulation and the corresponding shape ...
Geotechnical and Geological Engineering, 2018
Journal of Central South University, 2016
The higher order displacement discontinuity method (HODDM) utilizing special crack tip elements h... more The higher order displacement discontinuity method (HODDM) utilizing special crack tip elements has been used in the solution of linear elastic fracture mechanics (LEFM) problems. The paper has selected several example problems from the fracture mechanics literature (with available analytical solutions) including center slant crack in an infinite and finite body, single and double edge cracks, cracks emanating from a circular hole. The numerical values of Mode I and Mode II SIFs for these problems using HODDM are in excellent agreement with analytical results (reaching up to 0.001% deviation from their analytical results). The HODDM is also compared with the XFEM and a modified XFEM results. The results show that the HODDM needs a considerably lower computational effort (with less than 400 nodes) than the XFEM and the modified XFEM (which needs more than 10000 nodes) to reach a much higher accuracy. The proposed HODDM offers higher accuracy and lower computation effort for a wide range of problems in LEFM.
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Papers by Abolfazl Abdollahipour