نشریه روش های تحلیلی و عددی مهندسی معدن
پیاپی 33 (Winter 2023)

The goal of the current research is to make more comprehensive the elastoplastic stresses effects and oil reservoirs behave in solid phase. These stresses are largely caused by the behavior of subsurface fluid in reservoirs. In reservoir formations, there are frequently significant spatial changes at various length scales. Additionally, a number of physical events influence the flow model in various hierarchies. To fully describe the flow and deformation concerning all of these sizes, more computing power is required. One of the principal problems in the oil field business has always been how to describe, optimize, and simulate the behavior of the solid portion of oil reservoirs. To model fluid flow in reservoirs, deformable media, and porous media, more effectively, several scales must be taken into account. This approach is difficult in different scales, and the results of the simulation's speed, accuracy, and precision indicates this. A hybrid multi-physical multi-scale model has recently been developed as a solution to this problem. The goal of the current work is to update this model to represent solid-phase deformations better. For this improvement, the model is changed into a geomechanical model with the capacity to simulate a plastic region using an integrated yield function as well as using an implicit technique to solve convergence equations concurrently. The simulation outcomes demonstrate that the improved multi-scale mixed physical model is an effective model for modelling oil reservoirs with elastoplastic deformation. This model's calculation speed and accuracy have been tested, and the results are satisfactory. In addition, this paper modeled land subsidence, which Sokolova et al. claim is impacted by a lack of reservoirs, and it fits quite well with other studies. Results have demonstrated that plastic stresses affect both the rate of oil production and the behavior of subsidence. It can be included as a safety feature for infrastructure and oil surface plants.

Experimental and numerical methods (Particle Flow Code) were used to investigate the effect of echelon notches on the shear behavior of the joint’s bridge area in granite. A punch-through shear test was used to model the granite cracks under shear loading. Granite samples with dimension of 20 mm×150 mm×40 mm were prepared in the laboratory. Within the specimen model and near the edges, four edge notches were provided. Nine different configuration systems were prepared for notches. In these configurations, the length of each notch was taken as 3 cm, 4cm and 5 cm. Assuming a plane strain condition, special rectangular models were prepared with dimensions of 100 mm×100 mm using the particle flow code in two dimensions (PFC2D). Similar to those joints’ configuration systems in the experimental tests, i.e. 9 models with different rock bridge lengths and different rock bridge joint angles were prepared. The axial load was applied to the punch through the central portion of the model. This testing showed that the failure process was mostly governed by the rock bridge length and the rock bridge angle.  Shear strengths of the specimens were related to fracture pattern and failure mechanism of the discontinuities. It was shown that the shear behavior of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the rock bridge angle.  The strength of samples decreases with increasing the joint length. The failure pattern and failure strength are similar in both methods, i.e. the experimental testing and the numerical simulation.

An open-pit mine production planning begins with determining the ultimate pit limit of an open-pit mine. The ultimate pit limit solver selects blocks whose total economic value is maximum while meeting the slope constraints. In other words, a group of blocks that maximize a selected parameter, such as profit, metal content, or net present value, is considered in determining the ultimate pit limit. Also, the ultimate pit limit is designed to select the waste dump location, surface facilities, extractable reserves, and the amount of waste removal. The production planning problem in large-scale open-pit mines is referred to as an NP-hard problem because it cannot be solved in a reasonable computational time. To solve this, various methods, including aggregation methods, have been proposed to reduce the size of the issue. In this paper, to evaluate the efficiency of the block aggregation technique based on the pit values and computational times, at first, the heuristic Tabesh-AskariNasab aggregation algorithm was applied to the block models with 2400 and 11400 blocks. Then the ultimate pit limit based on the original block model and reconstructed block models were determined using the linear programming model. Comparing the results in both block models indicates that the block aggregation approach considerably decreased computational time while generating near-optimal pit values. These results are more critical in large-scale production planning problems, exactly in open pit mine scheduling. Furthermore, the slope of pit walls was decreased by increasing the size of clusters, and the stripping ratio increased in both block models.

The seismic response of the smart layer is studied in this article based on mathematical modeling and numerical solution. The structure is modeled by sinusoidal shear deformation (SSDT) and the motion equations are derived by energy method and virtual work. The concrete beam is covered by a piezoelectric layer for smart control of the structure. The differential quadrature (DQ) and Newark methods are applied for numerical solution and dynamic response of the smart concrete beam under the earthquake load. The influences of boundary conditions; external voltage, and geometrical parameters of the beam are studied on the seismic response of the smart concrete beam. The results indicate that by applying an external negative voltage, the dynamic deflection of the smart concrete beam is reduced, which is important for smart control of the system while this phenomenon is converse for positive external voltage.

The effect of mechanical properties of upstream tailings dams is investigated under seismic loads. For this, the finite-difference numerical method under the Finn-Byrne nonlinear elastoplastic constitutive model was implemented. Variations of elastic modulus and Poisson’s ratio in the typical range of tailings dam material were investigated in the phenomenon of liquefaction, horizontal displacement, and subsidence. The results showed that with increasing the elastic modulus of the dam body from 10 to 50 MPa, the maximum horizontal displacement, subsidence, and liquefaction coefficient in the dam body have increased 2.3, 3.5, and 2 times, respectively. Moreover, by increasing the Poisson’s ratio from 0.25 to 0.4, the maximum horizontal displacement, subsidence, and liquefaction coefficient in the dam body have raised 2.4, 2.3, and 1.75, respectively. The Poisson’s ratio of tailings had a significant effect on the liquefaction of the dam body. In which, increasing the Poisson’s ratio from 0.25 to 0.4, the maximum liquefaction coefficients were increased 1.75 times. Ultimately, it is concluded that despite the displacement which is not affected by the variation of tailings dam elastic modulus, the liquefaction coefficient is doubled by its variation, which may cause a serious threat to the stability of the dam.

The performance of mechanized excavation depends on the soil abrasivity and the resistance of cutting tools against wear. The wear has a negative effect on excavation machine parameters, such as penetration rate, and reduces the machine's efficiency. Worn tools require replacement, which interrupts the project and incurs high maintenance costs. For this reason, many efforts have been made to understand the interaction between soil and cutting tools. Various wear-measuring devices have been designed and built to measure soil abrasivity and cutting tool wear. In this research, to study the mechanism of tunnel excavation in the laboratory, a tunnel boring machine laboratory simulator was designed and built, and the effect of the operating parameters of the excavation machine on the average wear of cutting tools was studied. The features of this machine are its horizontal excavation, the low rotation speed of the cutterhead, continuous contact of the cutters with fresh soil during the test, and continuous injection of materials with a specific injection pressure during the test. Using the granulation of soil prepared from Tabriz metro line 2 in three moisture content of zero, 7, and 13%, the effect of the rotation speed of the cutterhead, rotation time, and penetration rate on the wear of cutting tools was studied. The investigations showed that with the increase in the rotation speed of the cutterhead, the average wear increases. Also, the increasing rotation time has caused more friction between the cutting tools and the cutterhead with the soil, and the wear has increased. The wear decreased with the increase in the penetration rate, despite the increase in the intensity of the conflict between the soil particles and the cutting tools. The results obtained from this research by using a tunnel boring machine laboratory simulator are in good agreement with previous studies.