Rock Mechanics
Navid Afrasiabi; Mehdi Noroozi; Ahmad Ramezanzadeh
Abstract
In this research, the effect of geometric parameters of closely joints on rock cutting efficiency by TBM disc cutter is studied using PFC3D software. A validated numerical model of linear cutting machine test is developed and the efficiency of disc cutter is investigated on rock mass specimens with different ...
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In this research, the effect of geometric parameters of closely joints on rock cutting efficiency by TBM disc cutter is studied using PFC3D software. A validated numerical model of linear cutting machine test is developed and the efficiency of disc cutter is investigated on rock mass specimens with different joint configurations (possible combination of dip angles of 30, 60, 90 degrees with joint spacings of 3, 5, 10, 15, 20 cm). Numerical modeling results reveal that in general, the joint spacing has a greater effect on rock cutting efficiency than joint orientation. If the joint spacing is less than 10 cm, the role of the joint angle is reduced and the distances between the joints control the efficiency. When the joints are close together and have a spacing of less than 10 cm, particularly 3 to 5 cm, the best cutting efficiency can be achieved for a joint angle of 90 degrees. The cutting coefficient is decreased by increasing the joint spacing and the maximum CC occurs at a joint spacing of 5 cm. For joint spacing more than 10 cm, the joints with a 90 degrees dip angle have the greatest impact on the specific energy and reduce cutting efficiency. The best disc cutter efficiency and the minimum required normal force is achieved when joint spacing is more than 10 cm and the angle between the joints and advance direction of the disc cutter is 60 degrees. In the tunnel excavation process, with increasing joint spacing, the TBM machine thrust is more important than its torque. The findings of this research provide a basis for predicting TBM efficiency through joint characteristics.
Rock Mechanics
Milad Manafi; Hamed Molladovoodi; Hamid Chakeri
Abstract
Tunneling in urban areas is associated with various challenges that must be carefully evaluated during pre-construction studies. Among these challenges, tunnel excavation through fault zones is particularly critical and has been widely investigated. Previous studies have primarily focused on the displacement ...
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Tunneling in urban areas is associated with various challenges that must be carefully evaluated during pre-construction studies. Among these challenges, tunnel excavation through fault zones is particularly critical and has been widely investigated. Previous studies have primarily focused on the displacement of tunnel linings under different fault movement conditions. In the present study, the effects of three key parameters, ground movement magnitude, grout layer thickness, and fault plane angle, on the induced bending moments and normal forces were examined. The numerical results indicate that ground movement magnitude has the most significant influence on induced stresses, whereas grout layer thickness and fault plane angle exhibit comparable effects. The analyses further show that a 100% increase in ground movement leads to a 60.67% rise in the induced normal force. Increasing the grout layer thickness reduces the induced forces by 32.9%, while a larger fault plane angle decreases the normal force by 34.52%. The modeling outcomes also reveal that grout layer thickness is the most influential factor effecting the induced bending moments. These findings provide valuable insights for evaluating the structural capacity and potential failure of tunnel lining crossing fault zones.
Rock Mechanics
vahab sarfarazi; amir rezaei; mohammad fatehi marji; mohammad omidi manesh
Abstract
This study provides an in-depth examination of the failure characteristics of rock salt samples subjected to punch shear testing, emphasizing the analysis of fracture processes and the material’s mechanical response. Given the diverse industrial applications of rock salt, the need for more detailed ...
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This study provides an in-depth examination of the failure characteristics of rock salt samples subjected to punch shear testing, emphasizing the analysis of fracture processes and the material’s mechanical response. Given the diverse industrial applications of rock salt, the need for more detailed studies in this field is evident. The study employs an integrated approach combining practical experiments and numerical simulations using PFC2D software. The results reveal that the failure response of rock salt is governed by critical factors such as the loading rate and the material’s inherent mechanical properties. Laboratory observations indicate that fractures primarily initiate from structurally weak zones, with stress concentration at contact areas being the main cause of tensile-shear failures in the samples. The findings of this study can serve as a foundation for establishing novel quality evaluation criteria for rock salt, underscoring the need for continued research efforts to improve safety and performance in related engineering applications.
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
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
Pankaj Bhatt; Anil Kumar Sinha; Mariya Dayana P J; Parvathi Geetha Sreekantan; Murtaza Hasan
Abstract
The rapid development of road networks needs huge construction materials. Mining and industrial wastes can be used as sustainable road construction materials and will be alternatives to fulfill the huge demand in road construction. Zinc tailing is one such mining waste and has the potential for road ...
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The rapid development of road networks needs huge construction materials. Mining and industrial wastes can be used as sustainable road construction materials and will be alternatives to fulfill the huge demand in road construction. Zinc tailing is one such mining waste and has the potential for road construction. This material was collected from Zawar mines (Rajasthan), and characterization was carried out for embankment/subgrade applications. A physical model test was conducted in the laboratory to examine the stress-settlement behaviour. To improve the modulus value of tailing, it was reinforced with geogrid in two different laying patterns, viz. layer/loop and stress-settlement behavior was studied. Different parameters were studied: reinforcement depth, layer of reinforcement, number of loops, and depth of loop of reinforcement. The experimental result was validated with the numerical finite element method (SoilWorks). Tailing comprises fine-grained silt-size particles (61%) with no swelling behavior and non-plastic nature. It has values of MDD and OMC as 1.86 g/cm3 and 11%, respectively. It has a higher value of CBR (12%) and internal friction angle (34.6o) with cohesionless nature. The variation of settlement with stress is linear for reinforced and unreinforced tailing fill. As the depth of reinforcement increases, settlement increases in both layer and loop reinforcement. The settlement trajectory obtained from a numerical method closely resembles that of a laboratory physical model, particularly when the applied stress is up to 600 kPa. The modulus of elasticity of tailing was significantly improved with the introduction of geogrid reinforcement either in layer or loop.
Rock Mechanics
Praveena Das Jennifer; Porchelvan P
Abstract
This paper presents a comprehensive study on the stability of the deep underground closed Kolar Gold Fields mine (3.2 km deep) under varying seismic loading conditions. The study utilized the Finite Element Method (FEM)-based Midas GTS NX software tool to conduct numerical simulations of seismic loads ...
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This paper presents a comprehensive study on the stability of the deep underground closed Kolar Gold Fields mine (3.2 km deep) under varying seismic loading conditions. The study utilized the Finite Element Method (FEM)-based Midas GTS NX software tool to conduct numerical simulations of seismic loads of varying intensities under multiple conditions of water level in the mine voids. The seismic loads applied were equivalent to the intensity of maximum mining-induced seismicity experienced in the mine. The study also examined the influence of the Mysore North Fault and its effects on the surface above the mining area. A seismic hazard vulnerability map of the mining area was developed based on the results for all simulated numerical model combinations. The results inferred that for a seismic load of PGA, 0.22 g, for fault and actual water level combination, very strong shaking and moderate potential surface damage were observed at vulnerable zones with a maximum PGA of 0.196 g and Peak Ground Velocity (PGV) of 0.49 m/s. The study highlights the importance of monitoring post-mining induced seismic activities using a dedicated microseismic monitoring system with sensors placed at the most vulnerable zone locations assessed from the numerical modelling studies carried out. Remedial measures suggested include regular dewatering of mine workings based on water accumulation and backfilling of mine voids with suitable fill material. The dynamic modelling approach using Midas GTS NX was found to be a more reliable, feasible, efficient, and simple method for assessing the stability of closed mines.
