Exploitation
Behnam Alipenhani; Mehran Jalilian; Abbas Majdi; Hassan Bakhshandeh Amnieh; Mohammad Hossein Khosravi
Abstract
The paper presents the effect of the dip of joints, joint spacing, and the undercutting method on the height of the caving in block caving. The obtained results show that among the three investigated parameters, respectively, the dip of joints, undercutting method, and joint spacing have the greatest ...
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The paper presents the effect of the dip of joints, joint spacing, and the undercutting method on the height of the caving in block caving. The obtained results show that among the three investigated parameters, respectively, the dip of joints, undercutting method, and joint spacing have the greatest effect on increasing the height of the caving zone. Comparing the data obtained from physical and numerical modeling shows a 97% match. Also, by increasing the joint spacing from 4 to 6 cm, 14%, from 6 to 8 cm, about 35%, and from 8 to 10, about 50%, the height of the caving zone has decreased. Regarding the dip of the joint, with the dip increasing from 30 to 45 degrees, about 3% of the caving height decreases. By increasing the dip of the joint from 45 to 60 degrees, the caving height has decreased by 42%. By increasing this value from 60 to 75 degrees, the caving height has increased by 50%. Also, changing the undercutting method from symmetric to advanced undercutting has increased the caving height by 40%. Additionally, three mathematical models have been proposed based on the shape of the caving zone in physical modeling.
M. Davood Yavari; H. Haeri; V. Sarfarazi; M. Fatehi Marji; H. A. Lazemi
Abstract
Investigating the crack propagation mechanism is of paramount importance in analyzing the failure process of most materials. This process may be exposed during each kind of loading on the materials. In this work, the cracking mechanism in rock-like materials is studied using the numerical methods and ...
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Investigating the crack propagation mechanism is of paramount importance in analyzing the failure process of most materials. This process may be exposed during each kind of loading on the materials. In this work, the cracking mechanism in rock-like materials is studied using the numerical methods and compared with the experimental test results. However, the mechanism of crack growth in brittle materials such as rocks is influenced by different parameters. This research work focuses on the effect of the initial crack angles on the crack growth paths of these materials. Some cubic samples containing pre-existing cracks are tested in compression by considering different flaw orientations. The specimens are made of cement, water, and sand. Moreover, the mentioned process is numerically simulated using three different methods: the finite difference method for discontinuous bodies or discrete element method, the displacement discontinuity method, and the versatile finite element method. The micro-parameters for simulation are gained by the trial-and-error procedure for the discrete element method. Eventually, the crack growth paths observed in the experiments are compared with the numerically simulated models. The results obtained show that these central cracks propagate in two ways, which are dependent on their initial angle. By increasing the initial crack angle to greater than 30° (α > 30°), the wing crack path moves further away from the initial crack, and by decreasing α to smaller than 30° (α < 30°), only the shear cracks are initiated. Therefore, the validity and accuracy of the results are manifested by comparing all the corresponding results obtained by different methods. Based on these results, it can generally be concluded that the strength of the cubic (rock material) specimens increases with increase in the crack angles with respect to the applied loading direction.
Rock Mechanics
E. Khorasani; M. Amini; M. F. Hossaini
Abstract
Bimrocks are complex geomaterials that are defined as mixtures of rocks composed of geotechnically significant blocks within a matrix of finer texture. Bimslopes are made from bimrocks and are usually seen in weathered and shallow environments. Some characteristics of blocks affecting the strength of ...
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Bimrocks are complex geomaterials that are defined as mixtures of rocks composed of geotechnically significant blocks within a matrix of finer texture. Bimslopes are made from bimrocks and are usually seen in weathered and shallow environments. Some characteristics of blocks affecting the strength of bimrocks include VBP (Volumetric Block Proportion), orientation, and arrangement, which have important roles in the stability of bimslopes. Previous studies show that bimrocks usually have a specific block size distribution, and for a bimslope with height of “H”, the size of blocks is changed from 0.05H to 0.75H. In this paper, the influence of large blocks position on bimslope stability was investigated by the physical and numerical models. The blocks that had a dimension larger than 0.5H were considered as “large blocks”. In this work, first, thirty physical models were created and tested using a titling table machine. These models have a specific block size distribution and VBP with ellipsoidal blocks. The main variable of the models is large blocks position, where three categories including lower part of bimslope, upper part of bimslope, and sporadic state are considered. Based on the results of physical trials, thirty numerical models at the laboratory scale were generated using the finite element method. After comparing the physical and numerical models, which showed a good accordance, the numerical models were developed to the natural scale. The theoretical bimslopes investigated in this work showed that the position of large blocks had a significant influence on the stability of bimslopes.
