Rock Mechanics
Mahdi Bajolvand; Ahmad Ramezanzadeh; Amin Hekmatnejad; Mohammad Mehrad; Shadfar Davoodi; Mohammad Teimuri; Mohammad Reza Hajsaeedi; Mahya Safari
Abstract
Bit wear is one of the fundamental challenges affecting the performance and cost of drilling operations in oil, gas, and geothermal wells. Since identifying the factors influencing bit wear rate (BWR) is essential, and the ability to predict its variations during drilling operations is influenced by ...
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Bit wear is one of the fundamental challenges affecting the performance and cost of drilling operations in oil, gas, and geothermal wells. Since identifying the factors influencing bit wear rate (BWR) is essential, and the ability to predict its variations during drilling operations is influenced by environmental and operational factors, this study aims to develop an Adaptive Bit Wear Rate Predictor (ABWRP) algorithm for estimating the BWR during drilling operations for new wells. The structure of this algorithm consists of a data transmitter, data processor, deep learning-based bit wear rate estimator, and a bit wear updating module. To develop a model for the BWR estimation module, data from two wells in an oil field in southwest Iran were collected and analyzed, including petrophysical data, drilling data, and bit wear and run records. Both studied wells were drilled using PDC bits with a diameter of 8.5 inches. After preprocessing the data, the key factors affecting the bit wear rate were identified using the Wrapper method, including depth, confined compressive strength, maximum horizontal stress, bit wear percentage, weight on bit, bit rotational speed, and pump flow rate. Subsequently, seven machine learning (ML) and deep learning (DL) algorithms were used to develop the bit wear rate estimation module within the ABWRP algorithm. Among them, the convolutional neural network (CNN) model demonstrated the best performance, with Root Mean Square Error (RMSE) values of 0.0011 and 0.0017 and R-square (R²) values of 0.96 and 0.92 for the training and testing datasets, respectively. Therefore, the CNN model was selected as the most efficient model among the evaluated models. Finally, a simulation-based experiment was designed to evaluate the performance of the ABWRP algorithm. In this experiment, unseen data from one of the studied wells were used as data from a newly drilled well. The results demonstrated that the ABWRP algorithm could estimate final bit wear with a 14% error. Thus, the algorithm developed in this study can play a significant role in the design and planning of new wells, particularly in optimizing drilling parameters while considering bit wear effects.
Rock Mechanics
Amin Jamshidi; Deniz Akbay
Abstract
Brazilian tensile strength (BTS) is an important parameter in mining activities, particularly in conditions that rocks are under tensile stresses. This test measures the indirect tensile strength of rocks, which is crucial for understanding the mechanical behavior and quality of rocks in the mining context, ...
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Brazilian tensile strength (BTS) is an important parameter in mining activities, particularly in conditions that rocks are under tensile stresses. This test measures the indirect tensile strength of rocks, which is crucial for understanding the mechanical behavior and quality of rocks in the mining context, including slope stability analysis, blast design, rock support systems, excavation and equipment selection, fracture propagation, and hydraulic fracturing and drilling. So far, no classification of tensile strength of rock for mining applications has been presented. In the present study, a new rock classification based on BTS for the various rocks was proposed. To achieve this purpose, by a reviewing previous studies, uniaxial compressive strength (UCS) and BTS of various rock classes, including igneous, sedimentary, and metamorphic were collected. For each rock class, the correlation equations between UCS and BTS were developed using simple regression analysis. Using data analyses, the rocks was categorized into to seven BTS classes. The findings revealed that igneous, sedimentary, and metamorphic rocks have a wide range of BTS values, and subsequent fall into the different BTS classes. The validity of BTS classification was verified using data of BTS and UCS of various rock classes published in the literature, and results showed that BTS can be as a suitable indicator for preliminary assessment of rock quality. This can lead to a better understand from the strength behavior of the rock under tensile stresses in site a mining activity, and therefore, a more accurate design of a mining project.
Rock Mechanics
Sina Alizadeh; Mohammad Reza Ghassemi; Mehran Arian; Ali Solgi; Zahra Maleki; Reza Mikaeil
Abstract
One of the most significant risks for investors in the dimension stone industry is the presence of natural discontinuities in the rock mass, which affect the quality of the extracted stone blocks. These discontinuities not only reduce extraction efficiency but also hinder the optimal utilization of the ...
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One of the most significant risks for investors in the dimension stone industry is the presence of natural discontinuities in the rock mass, which affect the quality of the extracted stone blocks. These discontinuities not only reduce extraction efficiency but also hinder the optimal utilization of the quarry. Therefore, it is essential to identify and analyze discontinuities in the rock before initiating any extraction activities and to assess the optimization of the extraction direction in dimension stone quarries. This study examines the key characteristics of discontinuities and joint sets, including their coordinates, strike, dip, spacing and aperture, in the Melika marble dimension stone quarry in Kerman. The collected data are then analyzed using 3DEC software to construct a quarry block model. Additionally, the azimuth rotation of different joint sets is investigated in four categories. The results obtained from the modeling indicate that, to achieve maximum blocking, the current extraction direction should be shifted 70° westward. This adjustment increases the number of blocks to 14,550, the average block volume to 5.5 m³, and the total volume of extracted stone to 79,918.9 m³. These changes are projected to generate approximately $3,180,000 in revenue for the quarry. The study highlights a practical optimization strategy that can significantly enhance the efficiency and profitability of dimension stone quarries by improving extraction direction based on discontinuity analysis.
Rock Mechanics
Farhad Mollaei; Ali Moradzadeh; Reza Mohebian
Abstract
The important aspects of this study are to estimate the mechanical parameters of reservoir rock including Uniaxial Compressive Strength (UCS) and friction (FR) angle using well log data. The aim of this research is to estimate the UCS and FR angle (φ) using new deep learning (DL) methods including ...
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The important aspects of this study are to estimate the mechanical parameters of reservoir rock including Uniaxial Compressive Strength (UCS) and friction (FR) angle using well log data. The aim of this research is to estimate the UCS and FR angle (φ) using new deep learning (DL) methods including Multi-Layer Perceptron (MLP), Long Short-Term Memory (LSTM), Convolutional Neural Network (CNN), and CNN + LSTM (CL) by well log and core test data of one Iranian hydrocarbon field. As only 12 UCS and 6 FR core tests of single well in this field were available, they were firstly calculated, and then generalized to other depths using two newly derived equations and relevant logs. Next, the effective input logs' data for predicting these parameters have been selected by an auto-encoder DL method, and finally, the values of UCS and φ angle were predicted by the MLP, LSTM, CNN, and CL networks. The efficiency of these four prediction models was then evaluated using a blind dataset, and a range of statistical measures applied to training, testing, and blind datasets. Results show that all four models achieve satisfactory prediction accuracy. However, the CL model outperformed the others, yielding the lowest RMSE of 1.0052 and the highest R² of 0.9983 for UCS prediction, along with an RMSE of 0.0201 and R² of 0.9917 for φ angle prediction on the blind dataset. These findings highlight the high accuracy of deep learning algorithms, particularly the CL algorithm, which demonstrates superior precision compared to the MLP method.
Rock Mechanics
Shahla Miri Darmarani; Erfan Khoshzaher; Hamid Chakeri
Abstract
Shotcrete is used as a component of the support system in tunnels, and one of the methods to enhance its mechanical properties is by incorporating fibers. Fibers can significantly improve the mechanical properties of shotcrete, including compressive and tensile strength. This leads to savings in time, ...
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Shotcrete is used as a component of the support system in tunnels, and one of the methods to enhance its mechanical properties is by incorporating fibers. Fibers can significantly improve the mechanical properties of shotcrete, including compressive and tensile strength. This leads to savings in time, cost, and post-installation maintenance. In recent years, due to the environmental pollution caused by the production of synthetic fibers, there has been increasing interest in using recycled materials, mainly recycled steel fibers from worn tires. The present study is a laboratory-based research program investigating the feasibility of using recycled fibers to improve the mechanical properties of shotcrete. In this study, recycled steel fibers from worn tires and shaves of basalt stone were used to create laboratory samples. The laboratory samples included cubic (10×10 cm) and cylindrical (15×30 cm) specimens with five different mix designs: ordinary shotcrete, shotcrete containing 0.5%, 1%, 1.5%, and 2% recycled fibers. These fibers were categorized into three length groups: coarse, mixed, and fine. The laboratory tests included compressive and tensile (Brazilian) strength tests at 3-day intervals. The results of the laboratory studies indicated that recycled fibers from worn tires could significantly enhance the mechanical properties of shotcrete, with a two-fold increase in compressive strength observed when the fiber content was increased by 2%. Moreover, the inclusion of basalt stone shaves not only improved the compressive strength of the samples but also had a substantial effect on enhancing the tensile strength.
Rock Mechanics
Amin Maleki; Hamid Chakeri; Hadi Shakeri; Erfan Khoshzaher; Mohammad Darbor
Abstract
Today, due to technological advancements and increasing demand, various types of Tunnel Boring Machines (TBM) are extensively used for tunneling in both soil and rock. The mechanical excavation method has become attractive in tunnel excavation and underground spaces due to its high safety, rapid progress ...
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Today, due to technological advancements and increasing demand, various types of Tunnel Boring Machines (TBM) are extensively used for tunneling in both soil and rock. The mechanical excavation method has become attractive in tunnel excavation and underground spaces due to its high safety, rapid progress rate, low human labor requirement, and mechanization capability. The high capital costs of mechanical excavation make it essential to conduct laboratory tests, such as linear cutting tests on rocks, before selecting the machine type and adjusting the cutter head blade. The main objective of this study is to investigate the impact of rock mechanical properties on the cutting tool wear using a newly developed small-scale Linear Cutting Machine (LCM). To achieve this, laboratory linear cutting tests on rocks were conducted after constructing the small-scale linear cutting machine. To evaluate the rock cuttability and analyze the performance of disc cutters, 5 rock samples were used at three different penetration depths of 1, 1.5, and 2 mm. The results showed that the wear values of the cutting discs increased with penetration depth in all rock types, with the highest wear observed in basalt. Additionally, Brazilian tensile strength exhibited the highest correlation with cutting disc wear parameters. Furthermore, these studies indicated that determining the mineralogical and physical characteristics of rocks, such as texture, crystal size, and porosity, alongside their mechanical properties, is crucial for predicting rock wear.
Rock Mechanics
Aram Ardalanzdeh; Seyed Davoud Mohammadi; Vahab Sarfarazi; Hossein Shahbazi
Abstract
Creating holes in rocks using different methods presents various challenges. In this research, an attempt was made to investigate these characteristics and the existing problems in creating holes based on the texture and brittleness of the rock. For this purpose, several core specimens were taken from ...
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Creating holes in rocks using different methods presents various challenges. In this research, an attempt was made to investigate these characteristics and the existing problems in creating holes based on the texture and brittleness of the rock. For this purpose, several core specimens were taken from the Alvand granitic batholith of Hamadan, and the petrological and textural indexes of the rocks were determined. There are four types of rock textures, ranging from coarse-grained to fine-grained. The texture coefficients (TC) for the four types of rocks (G1 to G4) were 1.709, 1.730, 1.774, and 1.697, respectively. The brittleness index (B1) for the four types of rocks (G1 to G4) were 9.13, 11.01, 12.07, and 10.65, respectively. After that, using a diamond drill, one hole was created in each rock core specimen, and at the end of drilling, a fracture pit was separated from the bottom of each hole in the specimen. The results show that as the mineral size decreases, the fracture pit depth also decreases, and in porphyry texture, the fracture pit depth is between the fracture pit depths of coarse-grained and medium-grained rocks. As the texture coefficient (TC) and brittleness of the rock specimens increase, the fracture pit depth decreases, and in porphyry texture, the fracture pit depth remains between the fracture pit depths of coarse-grained and medium-grained rocks. Finally, the results from laboratory tests indicate that creating holes using a drill to study the effect of the holes on rock behavior can cause damage to the rocks.
Rock Mechanics
Mohammad Amin HajiMohammadi; Mojtaba Bahaaddini; Mohammad Hossein Khosravi; Hassan Vandyoosefi
Abstract
Discontinuities are known as a primary factor in instability of tunnels and underground excavations. To prevent potential damage and overbreak by underground advancement, it is essential to provide a model, which considers both the geometrical and mechanical characteristics of discontinuities. Discrete ...
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Discontinuities are known as a primary factor in instability of tunnels and underground excavations. To prevent potential damage and overbreak by underground advancement, it is essential to provide a model, which considers both the geometrical and mechanical characteristics of discontinuities. Discrete Fracture Network (DFN) is a conceptual model to represent and analyse the complex system of discontinuities within the rock mass. Combined DFN with analytical or numerical methods can be employed as a scientific tool to analyse generated rock blocks, and their stabilities under different loading conditions. This paper aims to investigate the created overbreak by tunnel advancement in the Alborz tunnel located in the Tehran-North freeway in Iran. First, the geometrical characteristics of discontinuities were surveyed by tunnel advancement in 200 meters. Four major joint sets and a bedding plane were identified and their statistical characteristics were measured. The DFN model was generated and its validity was investigated through a comparison against field data. The average volume of generated blocks in the studied area was measured 0.22 m3. The stability of generated blocks around the opening was kinematically evaluated. The volume of formed blocks around tunnel in the DFN model prone to instability due to static or dynamic loads was estimated 2605 m3 while the measured overbreak in field was 2735 m3. The depth of overbreak in DFN model showed a good agreement with field measurements. The results show that DFN model combined with kinematic stability analysis can provide a scientific tool to investigate geological overbreak in underground excavations.
Rock Mechanics
Mohammad Reza Zeerak; Mohammad Fatehi Marji; Manouchehr Sanei; Mehdi Najafi; Abolfazl Abdollahipour
Abstract
The Extended Finite Element Method (XFEM) is a leading computational approach for studying crack growth in rocks, as it can effectively model complex crack paths and discontinuities without the need for re-meshing. In this context, XFEM is particularly well-suited for simulating the development of hydraulic ...
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The Extended Finite Element Method (XFEM) is a leading computational approach for studying crack growth in rocks, as it can effectively model complex crack paths and discontinuities without the need for re-meshing. In this context, XFEM is particularly well-suited for simulating the development of hydraulic fractures. XFEM is employed to investigate crack initiation, propagation, and aperture size in rock formations, with validation using a Boundary Element Method (BEM)-based approach. Three scenarios are analyzed for crack orientation and interaction in: single cracks at and crack displacement behavior at and multiple cracks at and . Displacement in the vertical direction (U2) and stress distribution around the crack tip in the S22 direction are examined to understand fracture mechanics parameters. The findings highlight that crack at higher angles, such as , exhibit more straightforward propagation, while those at or beyond often require additional stress to continue growing. The comparison between XFEM and BEM results confirms the reliability of the numerical approach, demonstrating strong agreement in predicting fracture behavior in rock materials. The results provide deeper insights into fracture evolution, stress intensity factors, and fracture toughness in geological media. These simulations advance computational fracture mechanics, contributing to optimizing hydraulic fracturing techniques for improved efficiency and safety in subsurface formations. This study is limited to 2D geometries and isotropic materials, potentially missing 3D heterogeneous subsurface complexities. Future work could explore 3D models, anisotropy, and fluid pressure/thermal effects to improve crack growth predictions.
Rock Mechanics
Weiqun Liu; Tian Fang; Sheng Sang
Abstract
Mudstone is a common rock in underground engineering, and mudstone with fractures, have the certain self-closing capability. In this paper, we employed experiments and numerical analyses to investigate the mechanism of such a characteristic, and also examined the permeability pattern of mudstone overburdens. ...
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Mudstone is a common rock in underground engineering, and mudstone with fractures, have the certain self-closing capability. In this paper, we employed experiments and numerical analyses to investigate the mechanism of such a characteristic, and also examined the permeability pattern of mudstone overburdens. The experiments were performed with the MTS815.02 testing system, involving material properties under different water contents and their crack-closing behaviors. The principal task of numerical analysis is to determine the permeability of fractured mudstone layers, working with the COMSOL platform. The experimental results show that the Young’s Modulus of water-saturated mudstone is just 2.2% of that of natural mudstone, and the saturated also exhibit a remarkably obvious creep behavior. As the surrounding pressures increase, the permeability coefficient of fractured mudstone decrease exponentially, even dropping by two orders of magnitude corresponding to over 2.0MPa pressures. Based on these experiment outcomes, we can easily infer that rapid or complete fracture-closing is the main reason of permeability drop, and furthermore, both softening and creep are the major factors of self-closure of mudstone fractures, and especially, the softening behavior plays an absolutely fundamental role. The numerical analyses show that either a higher in-situ stress or lower fracture density can obviously become one of the advantageous conditions for fractured mudstone layers to restore towards impermeability. These results are also verified by the engineering observation in Yili No. 4 mine of China. There obviously existed the recovery of water-blocking capacity of overlying strata after a period of time. We hereby recommend this investigation as refences for underground mining or engineering construction involving mudstone.
Rock Mechanics
Festus Kunkyin-Saadaari; Jude Baah Offei; Sadique Ibn Sadique; Victor Kwaku Agadzie; Ishamel Abeiku Forson
Abstract
The underground mining operations at the Obuasi Gold Mine rely heavily on the stability of hard rock pillars for safety and productivity. The traditional empirical and numerical methods for predicting pillar stability have limitations, prompting the exploration of advanced machine learning techniques. ...
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The underground mining operations at the Obuasi Gold Mine rely heavily on the stability of hard rock pillars for safety and productivity. The traditional empirical and numerical methods for predicting pillar stability have limitations, prompting the exploration of advanced machine learning techniques. Hence, this work investigates the applicability of stacked generalisation techniques for predicting the stability status of hard rock pillars in underground mines. Four stacked models were developed, using Gradient Boosting Decision Trees (GBDTs), Random Forest (RF), Extra Trees (ET), and Light Gradient Boosting Machines (LightGBMs), with each model taking turns as the meta-learner, while the remaining three models acted as the base learners in each case. The models were trained and tested on a dataset of 201 pillar cases from the AngloGold Ashanti Obuasi Mine in Ghana. Model performance was evaluated using classification metrics, including accuracy, precision, recall, F1-score and Matthews Correlation Coefficient (MCC). The RF-stacked model demonstrated the best overall performance, achieving an accuracy of 93.44%, precision of 94.27%, recall of 93.44%, F1-score of 93.59%, and MCC of 88.90%. Feature importance analysis revealed pillar depth and pillar stress as the most influential factors affecting pillar stability prediction. The results indicate that stacked generalisation techniques, particularly the RF-stacked model, offer promising capabilities for predicting hard rock pillar stability in underground mining operations.
Rock Mechanics
Mohammad Rezaei; Seyed Pourya Hosseini; Danial Jahed Armaghani; Manoj Khandelwal
Abstract
This paper presents an experimental-statistical study investigating the influence of five joint properties: density, filling type, angle, aperture, and roughness on the longitudinal wave velocity (LWV) of concrete samples. To achieve this, each of the five properties is categorized into distinct groups ...
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This paper presents an experimental-statistical study investigating the influence of five joint properties: density, filling type, angle, aperture, and roughness on the longitudinal wave velocity (LWV) of concrete samples. To achieve this, each of the five properties is categorized into distinct groups with specific intervals. Concrete samples measuring 15*15*15 cm are prepared in the laboratory based on an optimal combination of 75% sand, 15% cement, and 10% water. The LWV values of these samples are then measured. The experimental results indicate that joint density, roughness, and aperture have an inverse relation with LWV, resulting in reductions of 82%, 22.5% and 49%, respectively. Additionally, an approximate sinusoidal relationship between LWV and joint angle is established, leading to a variation of approximately 10% in LWV values for different joint angles. To evaluate the effect of joint filling on LWV, various filling materials, including iron oxide, calcite, silica, clay, and gypsum are used, resulting in approximately a 34% variation in LWV values. It was found that gypsum filling yields the highest LWV value while iron oxide filling produces the lowest. Furthermore, analysis of variance (ANOVA) confirms that a polynomial quadratic equation best represents the relation between LWV and each of the joint characteristics, with determination coefficient (R2) values ranging from 0.694 to 0.99. Finally, a verification study using "validation samples" demonstrates the acceptable accuracy for the proposed equations, with minimum relative errors ranging from 3% to 13%, a low root mean square error of 189.08 m/s, and a high R2 value of 0.926. This research enhances understanding of wave propagation through jointed rock masses with varying joint characteristics and provides theoretical support for rock reorganization and dynamic stability analysis of rock masses.
Rock Mechanics
Ehsan Taheri; Reza Mohammadpour; Mohammad Hossein Mokhtarzadeh
Abstract
In recent years, the demand for new trenchless methods has dramatically risen. Pipe jacking is a trenchless method widely used in recent years. Ground deformation is one of the significant parameters that may lead to unrepairable harm to facilities and even people. So, ground deformation analysis is ...
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In recent years, the demand for new trenchless methods has dramatically risen. Pipe jacking is a trenchless method widely used in recent years. Ground deformation is one of the significant parameters that may lead to unrepairable harm to facilities and even people. So, ground deformation analysis is necessary for safety and design reasons. The present study analyzes the factors affecting ground deformation during pipe jacking. This is a descriptive-interventional study. Pipe jacking causes soil displacement in three dimensions (3-D). Therefore, 3-D numerical methods were applied for analysis. In this study, numerical simulation was performed using PLAXIS finite element numerical software, taking the case study into account. The effect of each parameter on the ground deformation pattern was studied in three directions; the uplift and their exact position were then analyzed. It should be noted that displacement analyses were performed in two areas: pipe crown and ground surface. Also, the relation of each parameter was estimated with the ground subsidence. Finally, the effect of each different factor and their sensitivity index were determined using sensitivity analysis. The highest subsidence occurs at the end of the shield due to stress relaxation. Considering the results, it was found that the relationship between the internal friction angle and subsidence is linear and direct. The relationship between the elastic modulus and subsidence is also linear but indirect. The results indicate that the most sensitive factor of ground deformation is the diameter, but the least sensitive factor is the face pressure.
Rock Mechanics
Dariush Kaveh Ahangaran; Kaveh Ahangari; Mosleh Eftekhari
Abstract
Blast damage on the stability of the slopes plays an important role in the profitability and safety of mines. Determination of this damage is also revealed in the widely used Hoek-Brown failure criterion. Of course, this damage is used as a moderating factor in this failure criterion, and its accurate ...
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Blast damage on the stability of the slopes plays an important role in the profitability and safety of mines. Determination of this damage is also revealed in the widely used Hoek-Brown failure criterion. Of course, this damage is used as a moderating factor in this failure criterion, and its accurate determination is considered an important challenge in rock engineering. This study aims to investigate the effect of geological structures in blast damage factor using 3D discrete element modeling of two slopes with different directions of geological discontinuities. The dynamic pressure of the explosion is also simulated in three blastholes. To ensure the modeling results, other dynamic properties of the model have been selected based on the proven studies. An analytical analysis was conducted based on the failure zones (blast damage area), and quantitative and qualitative analyses were performed using the recorded PPV values during the blasting simulation. The results show that the geological discontinuities control, damp, and reduce blast damage. The expansion of blast damage is reduced by 75% along with the increase in rock mass strength, and the blast damage can expand up to 33 meters along with the decrease in strength. By reducing the distance of discontinuities, the role of discontinuities in damping becomes greater than other properties of the rock mass and the discontinuities further away from the blasting hole create more damping. The relation between the distance from the Hole and PPV values shows that for more realistic slope stability analysis results, the values of the damage factor in the Hoek-Brown failure criterion should be applied gradually and decreasingly in layers parallel to the slope surface.
Rock Mechanics
Amirhossein Naseri; Behnam Maleki; Tohid Asheghi Mehmandari; Amin Tohidi; Ahmad Fahimifar
Abstract
The present study delves into investigating the impact of sample size and geometry on the mechanical behavior of rock and concrete. More specifically, it examines factors including Uniaxial Compressive Strength (UCS), Elastic Modulus (E), and Pressure Wave Velocity (Vp). Results indicated a notable correlation ...
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The present study delves into investigating the impact of sample size and geometry on the mechanical behavior of rock and concrete. More specifically, it examines factors including Uniaxial Compressive Strength (UCS), Elastic Modulus (E), and Pressure Wave Velocity (Vp). Results indicated a notable correlation between the dimensions and morphology of the specimens with these properties. All tests were conducted at a uniform loading rate of 0.002 mm/s. According to the outcomes, the effect of sample size and shape on UCS for concrete is more predictable than for rock. The increase in the sample size led to an initial increase followed by a decline in the UCS values of the rocks. Furthermore, the concrete typically showed a drop in the UCS values as sample size increased. The UCS and E values rose at first before falling, suggesting the existence of a sample size with maximum UCS. The Vp values of the prismatic rock and concrete samples continually grew. After attaining their optimum strength, the prismatic samples showed greater degrees of flexibility and ductility compared to cylindrical ones because of post peak behavior. This suggests that prismatic samples, with their less slender geometry and reduced tendency for brittle behavior, are deemed more suitable for UCS testing. These results can improve the accuracy of assessing the mechanical properties of tunneling materials, particularly those used in subsurface construction in urban roads and highways.
Rock Mechanics
Aref Jaberi; Shokroallah Zare
Abstract
Unlike the mechanical properties of intact rock, which can be obtained on a laboratory scale, estimating the mechanical properties of the jointed rock mass is very difficult due to the presence of different joints and the complexity of the joints. Therefore, to calculate the mechanical parameters of ...
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Unlike the mechanical properties of intact rock, which can be obtained on a laboratory scale, estimating the mechanical properties of the jointed rock mass is very difficult due to the presence of different joints and the complexity of the joints. Therefore, to calculate the mechanical parameters of the jointed rock mass and use the continuous media theory of the jointed rock mass, it is necessary to calculate the Representative Element Volume (REV) of the rock mass. In this study, the Discrete Element Method (DEM) and the mechanical index of strength were used to investigate the effect of persistent and non-persistent joint angles, as well as model size on the REV in x, y, and z directions. The numerical results showed that by changing the joint angles and side length, both the strength and the REV of the rock mass were affected. The maximum representative side length for the persistent joint in the x and z directions occurred at angles of 60° and 75°, respectively. The minimum strength was obtained for joints in the x and z directions at a 45° angle. Finally, the REV for persistent and non-persistent joints is calculated as 10*0.5*8m and 4*0.5*4m, respectively.
Rock Mechanics
RADHA TOMAR; SMITA TUNG
Abstract
Slope failures are prevalent issue in the construction sector. Thus the engineers must use appropriate slope stabilization techniques to reduce the risk of human life and property. This work investigates the efficacy of multiple regression analysis in predicting slope stability, specifically focusing ...
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Slope failures are prevalent issue in the construction sector. Thus the engineers must use appropriate slope stabilization techniques to reduce the risk of human life and property. This work investigates the efficacy of multiple regression analysis in predicting slope stability, specifically focusing on the slopes in the Kullu district, Himachal Pradesh, India. A total of 160 cases with different parameters were analyzed by using the well-known Limit Equilibrium Method (LEM), Morgenstern and Price on PLAXIS LE. Numerical analysis was performed using different nail lengths (6 m, 8 m, 10 m, and 12 m) and nail inclinations (0°, 5°, 10°, 15°, 20°, 25°, 30°, and 35°), applied to a homogeneous soil slope with 45°, 50°, 60°, and 70° inclinations, respectively. The limit equilibrium analysis may not offer predictive capabilities for future scenarios directly. In contrast, Multiple Regressions (MR) can provide predictive insights based on the historical data, allowing for forecasting of stability under different conditions or design scenarios. The utilization of MR provides the coefficients that quantify the influence of each variable on slope stability, enabling a detailed understanding of how each factor contributes. To develop the prediction models using Multiple Regression Analysis (MRA), the factor of safety values obtained by the numerical method were used. The accuracy of this model was evaluated against the conventional LE methods. The results indicate that multiple regression provides a good predictive performance with an R2 value equal to 0.774, offering a more nuanced and accurate assessment of slope stability compared to the traditional LE techniques.
Rock Mechanics
Hamed Farajollahi; Mohammad Mohammadi; Mohammad Hossein Khosravi
Abstract
A better understanding of rock mass behavior is an essential part of the design and construction of underground structures. Any improvement in the understanding of the behavior of rock mass will facilitate the improvement of the design in terms of the safety of the working environment, long-term safety ...
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A better understanding of rock mass behavior is an essential part of the design and construction of underground structures. Any improvement in the understanding of the behavior of rock mass will facilitate the improvement of the design in terms of the safety of the working environment, long-term safety of the structure, environmental effects, and sound management of public or private resources. Thus, in step one in this paper the experience gained from the application of the GDE (Geo Data Engineering) multiple graph approach for rock mass classification and assessment of its behavior through the course of excavation of the Alborz tunnel is presented. The predicted hazards are compared with the experienced problems and suggestions are given to be considered in future works of tunnel construction. In step two, the GDE multiple graph approach is compared to the rock mass behavior types proposed by Palmstrom & Stille (2007) in terms of the continuity of rock mass. The result of this comparison together with the data obtained from rock mass classification in the Alborz tunnel are used to develop a system that determines the applicability of the rock bolt supporting factor (RSF) in different rock mass behavior classes.
Rock Mechanics
Mohammad Rezaei; Seyed Zanyar Seyed Mousavi; Kamran Esmaeili
Abstract
This study introduces a novel approach, known as Hybrid Probabilistic Slope Stability Analysis (HPSSA), tailored for Mine 4 of the Gol-E-Gohar iron complex in Iran. The mine walls are first divided into 8 separate structural zones, including A-A' to H-H' sections for slope stability analysis. Then, sufficient ...
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This study introduces a novel approach, known as Hybrid Probabilistic Slope Stability Analysis (HPSSA), tailored for Mine 4 of the Gol-E-Gohar iron complex in Iran. The mine walls are first divided into 8 separate structural zones, including A-A' to H-H' sections for slope stability analysis. Then, sufficient core specimens are prepared from 22 drilled boreholes and the required parameters for slope design, including cohesion (c), friction angle (φ), and unit weight (γ), are measured. Finally, the HPSSA approach is performed through the combination of Monte Carlo simulation (MCS), Mohr-Coulomb criterion and Bishop's technique. According to the HPSSA results, the normal distribution function is achieved as the best curve fit for c, φ and γ parameters. Also, the obtained values of mean probabilistic safety factor (SF) for defined structural zones vary from 0.93 to 1.86, with the probability of failure (PF) of 0 to 75.6%. Moreover, SF values varied from 0.68 to 1.22 (mean value of 0.93) with a PF of 75% for the A-A' section and from 0.65 to 1.24 (mean value of 0.97) with a PF of 60% for the H-H' section. Hence, it is concluded that the A-A' section and mine’s north wall are more prone to instability with PF>60%. On the other hand, SF>1.2 and PF<5% for other mine walls (sections B-B'-G-G') prove that they are highly unlikely to be unstable. Displacement monitoring of the pit walls using installed prisms confirmed that average displacements in structural zones have a similar trend with SF values of the HPSSA. The results show a good agreement between the trend of probabilistic SFs and monitored slope displacements. Lastly, comparative analysis confirmed the validity of the suggested HPSSA approach with relatively higher accuracy than most previous slope stability analysis methods.
Rock Mechanics
Jagdish Lohar; Neha Shrivastava
Abstract
India is a leading producer and exporter of dimensional marble. The processing of marble into dimensional and finished forms involves sawing, grinding, and polishing, generating significant quantities of Marble Processing Waste (MPW). Efforts for bulk recycling of MPW from the rapidly expanding marble ...
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India is a leading producer and exporter of dimensional marble. The processing of marble into dimensional and finished forms involves sawing, grinding, and polishing, generating significant quantities of Marble Processing Waste (MPW). Efforts for bulk recycling of MPW from the rapidly expanding marble industry are essential due to significant environmental impacts, hindered by limited inclusion rates and complex processing requirements in current practices. Concurrently, the increased demand for geotechnical fill materials and the depletion of natural soils necessitates sustainable alternatives. Using MPW in geotechnical fills offers a viable solution, yet it lacks comprehensive characterization. The aim of this study is to evaluate MPW as a sustainable alternative to conventional geotechnical fill materials. In this study, a comprehensive analysis of MPW's physical, geotechnical, and electrochemical properties, along with its mineralogical, elemental, and chemical composition, was conducted. The findings show that MPW, being non-plastic and non-swelling with a grain size distribution and hydraulic conductivity similar to silty sands, can be used directly from disposal sites without further processing. Notably, MPW achieves a maximum dry density of 1.84 g/cm³ and exhibits internal friction angles of 36.5°, ensuring stability. Electrochemical analysis indicates low leachability risks, with pH levels of 8.1 and electrical resistivity of 6,200 ohm-cm. Scanning Electron Microscopy images reveal that MPW particles are irregular, with considerable angularity and surface roughness. These results position MPW as a viable and environmentally friendly alternative to conventional fill materials, with the potential to significantly reduce the exploitation of natural resources and advance sustainable waste management practices.
Rock Mechanics
Ajay Sharma; Neha Shrivastava
Abstract
The present study aims to assess the utility of construction and demolition (C&D) waste, specifically recycled concrete aggregates (RCA) and recycled brick aggregates (RBA), as fill materials in highway embankments. The assessment of slope stability is crucial in determining the suitability of any ...
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The present study aims to assess the utility of construction and demolition (C&D) waste, specifically recycled concrete aggregates (RCA) and recycled brick aggregates (RBA), as fill materials in highway embankments. The assessment of slope stability is crucial in determining the suitability of any material for embankment fill. GeoStudio software is employed in this study for slope stability assessment of 12 models with LS, RCA, RBA, and their blends as embankment fill materials. The embankment configuration is designed to represent a six-lane highway (carriageway width = 13 m, adhering to IRC: 36 standards), featuring varying slope elevations (3 m, 6 m, and 9 m) and diverse horizontal to vertical slope ratios (H:V = 2:1, 1:1, 1:2, and 1:3). The Morgenstern-Price method is employed to analyze slope stability and determine factor of safety (FOS) values. The study highlights the impact of slope heights, slope ratios, and fill materials (RCA, RBA, LS, and their blends) on FOS values in embankment models. Incorporating RCA or RBA in LS significantly boosts embankment FOS, exceeding stability expectations beyond 45˚ slope angles, potentially reducing costs and required area in construction projects. The incorporation of RCA/RBA into LS increases the FOS values to a range of 1.38 to 5.91, indicating very stable slopes for highway embankments. Based on the findings, replacing LS with RCA or RBA in embankment fill can enhance environmental sustainability and economic efficiency. However, these slope stability results apply specifically to C&D waste with similar composition, grain size, geotechnical properties, and embankment conditions.
Rock Mechanics
Manendra Singh; Moqin Mushtaq Zargar; Vivek Kumar Sharma; Ritu Raj Nath
Abstract
Non-structural slope stabilization techniques are gaining popularity for cost-affordability and environmental sustainability and are intended primarily to enhance the soil shear strength parameters. The present study evaluates the performance of three biopolymers: Guar Gum, Gellan Gum, and Xanthan Gum ...
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Non-structural slope stabilization techniques are gaining popularity for cost-affordability and environmental sustainability and are intended primarily to enhance the soil shear strength parameters. The present study evaluates the performance of three biopolymers: Guar Gum, Gellan Gum, and Xanthan Gum as slope stabilizers for a quintessential soil slope of a local district in the foothills of the Lesser Himalayas. The study measures the shear strength of biopolymer-treated soil at varying concentrations and moisture contents, and concludes that the soil shear strength is highly influenced by the concentration of biopolymer and the moisture content. The results demonstrate significant increase (48% and 7%) of the cohesion and friction angle of a particular biopolymer-treated sample for a specific moisture content. However, the addition of biopolymers to the soil also leads to a decrease in the permeability of the original sample. The study, in the next phase, numerically computes the Factor of Safety of the test-bed slope before and after the application of biopolymers, and observes that the addition of biopolymers in soil significantly increases (34%) the factor of safety at an optimum combination concentration and moisture content for all three biopolymers. This signifies their utility as non-structural slope stabilizers. By highlighting the improved shear strength of the biopolymer-treated soils, the study complements the current initiatives for non-structural slope stabilization and sustainable soil enhancement and adds to the new yet expanding body of information regarding long-term, non-structural slope stabilizing techniques.
Rock Mechanics
Kapoor Chand; Ved Kumar; Priyanshu Raj; Nikita Sharma; Amit Kumar Mankar; Radhakanta Koner
Abstract
Failure of tailings dams is a major issue in the mining industry as it critically impacts the environment and life. A major cause of the failure of tailings dams is the unplanned depositing of tailings and the increase in saturation due to rainfall events. This study using numerical modelling and artificial ...
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Failure of tailings dams is a major issue in the mining industry as it critically impacts the environment and life. A major cause of the failure of tailings dams is the unplanned depositing of tailings and the increase in saturation due to rainfall events. This study using numerical modelling and artificial intelligence techniques (like MLR, SVR, DT, RF, and XGB) aims to predict the slope stability of tailings dams to avoid failure. The stability of tailings dams is analysed using the finite difference method (FDM), which computes the factor of safety (FoS) using the shear strength reduction (SSR) technique. This investigation mainly focuses on the geotechnical and geometric parameters of the tailings dam, such as density, cohesion, friction angle, saturation, embankment height, slope angle and haul road width. Results of numerical modelling have been used for developing ML models and predicting slope stability. The efficiency of ML models was analysed based on the R2 and root mean square error (RMSE), mean squared errors (MSE), and mean absolute error (MAE). The XGB algorithm proved to be the most effective as it gave the highest accuracy and lowest RMSE value compared to other ML models. AI tool was developed based on the ML model results for dam slope stability prediction. The developed AI tool will help understand the role of saturation and geometry parameters in embankment stability at the initial level of investigation.
Rock Mechanics
Vahab Sarfarazi; Lei Zhou; Hadi Haeri; Parastou Salehipour; Ali Elahi; Ali Moayer; Mohammad Fatehi Marji
Abstract
The mechanical behavior of rock-rock bolt interface considering the effects of indents’ shape and their number was numerically simulated based on discrete element method using the two-dimensional particle flow code. The conventional and standard uniaxial compressive and Brazilian tensile strengths ...
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The mechanical behavior of rock-rock bolt interface considering the effects of indents’ shape and their number was numerically simulated based on discrete element method using the two-dimensional particle flow code. The conventional and standard uniaxial compressive and Brazilian tensile strengths tests were used to calibrate the modelled samples with 100 cm 100 cm in dimension. The numerical models were prepared such that different indent shape and number were inserted in the cable bolts arrangements during the rock reinforcement process. The effects of confining pressure 3.7 MPa and different shear failure loads were modeled for the punch shear test of the concrete specimens. The results of this study showed that the dominant failure mode of the rock-cable bolt interface was of tensile mode and the shape and number of cable indents significantly affected the strength and mechanical behavior of the modelled samples. It has also been showed that the indent dimensions and number affected the shear strength of the interfaces.
Rock Mechanics
Masoud Yazdani; Mohammad Fatehi Marji; Mehdi Najafi; Manouchehr Sanei
Abstract
Around 70% of the world's hydrocarbon fields are situated in reservoirs containing low-strength rocks, such as sandstone. During the production of hydrocarbons from sandstone reservoirs, sand-sized particles may become dislodged from the formation and enter the hydrocarbon fluid flow. Sand production ...
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Around 70% of the world's hydrocarbon fields are situated in reservoirs containing low-strength rocks, such as sandstone. During the production of hydrocarbons from sandstone reservoirs, sand-sized particles may become dislodged from the formation and enter the hydrocarbon fluid flow. Sand production is a significant issue in the oil industry due to its potential to cause erosion of pipes and valves. Separating grains from oil is a costly process. Oil and gas companies are motivated to reduce sand production during petroleum extraction. Hydraulic fracturing is one of the parameters that can influence sand production. However, understanding the complex interactions between hydraulic fracturing mechanisms and sand production around wellbores is critical for optimizing reservoir recovery and ensuring the integrity of production wells. This article explores the integrated simulation approach to model hydraulic fracturing processes and assess their effects on sand production. Two-dimensional models were created using the discrete element method in PFC2D software for this research. The fractures' length in the models varies based on the well's radius. The angle between two fractures at 90 and 180 degrees to each other was also modeled. In the first case, the length of the fracture is less than the radius of the well, in the second case, the values are equal and finally, the fracture length is assumed to exceed the well radius. The calibrated and validated results demonstrate the change in sand production rate in comparison to the unbroken state.
