نشریه روش های تحلیلی و عددی مهندسی معدن
پیاپی 37 (Winter 2024)

In this study, the penetration rate of the excavation machine in Tabriz Metro Line 2 using geotechnical parameters and neural networks is estimated. For this purpose, through comprehensive analysis, including borehole drilling, field and laboratory tests, and consideration of similar projects, the geotechnical parameters for soil and rock layers have been determined. Preprocessing data techniques, such as normalization, have been applied to address challenges such as noise and bias in raw data. Also, neural networks with varying architectures were evaluated using mean square error and correlation coefficient as evaluation metrics. The architecture (1-12-8) of this research demonstrates superior performance with a mean square error of 1.630 and a correlation coefficient of 0.932. This shows a strong relationship between predicted and actual penetration rate values. The findings of this research highlight the effectiveness of neural networks in estimating the penetration rate. Accurate estimations of the non-linear penetration rate were achieved by employing a single-layer neural network with multiple neurons using appropriate transfer functions. Overall, this research contributes to the understanding of geotechnical considerations for urban train routes and demonstrates the accuracy of neural networks for penetration rate estimation. These insights have implications for the design and engineering of similar projects.

In the topics related to rock mechanics and geotechnics, elastoplastic criteria are of special importance. This importance makes their numerical implementation necessary. Although most of the existing software in the field of rock mechanics and geotechnics have elastoplastic criteria, the lack of access to their coding core makes it practically impossible for researchers to develop them. Therefore, considering the importance of elastoplastic criteria and the complexity of their implementation, in this study, a suitable scheme was presented to improve the elastoplastic numerical integration algorithm of Darker-Prager criteria. The developed algorithm includes two steps of elastic trial and plastic return-mapping algorithm. In the proposed model, if the elastic trial step is in the elastic domain or on the yield surface, the answer of elasticity is approved. Otherwise, if the trial stress can not confirm the desired conditions in the first step, it is executed by the plastic return-mapping algorithm. This process has been done comprehensively and separately for Drucker-Prager's cone and apex to be able to express the elastoplastic behavior of the material optimally. The presented model was analyzed for the porous rock sample and its validation was confirmed by comparing the numerical results with the laboratory data.

The induced polarization (IP) response in media containing clay and/or metallic minerals has been modeled in different research. Increasing the IP applications and measurements has revealed these models’ limitations. For instance, no model has described IP response in the media with metallic minerals higher than 22 percent. So, our goal in this contribution is to explain the IP response of clay-rich samples containing low- to high-grade pyrite, galena, and sphalerite from the Zn-Pb sedimentary-exhalative mine Koushk, central Iran. The samples’ background consists of clayey/micaceous minerals, including illite, muscovite, and chlorite, that, along with the metallic minerals, make the consecutive layers in some samples, while others have a different formation. The samples also contain some insulating grains such as quartz and gypsum. Therefore, there are different conduction and polarization mechanisms in them. These properties make our samples unique and substantial to study the IP response. To do this, we measured the samples’ complex conductivity, density, porosity, cation exchange capacity (CEC), and metallic/non-metallic minerals. Then, we investigated the relationship between electrical and petrophysical properties. The results showed that the chargeability has no relationship with CEC and is a complete representation of the metallic minerals’ polarization. The normalized chargeability depends linearly on the quadrature conductivity and is affected by the metallic minerals besides CEC. The content and type of clay/mica minerals control the CEC. Hence, the normalized chargeability is influenced by the metallic and non-metallic polarizable components. The conductivity linearly relates to metallic minerals’ content and, in vein mineralizations, has higher values than disseminated ones. Ultimately, comparing our samples’ IP response with Revil et al.’s and Pelton et al.’s models for chargeability, metallic minerals volume content, and time constant determined that increasing the metallic minerals makes the chargeability decrease and the time constant increase. So, in high-grade porous media or non-dispersive formations, chargeability is a function of the metallic minerals’ volume content and the time constant. Complex media like our samples are expected in geological environments. Hence, recognizing the parameters affecting IP response in these media helps to better understand their properties and, in general, IP response characteristics.

Today, numerous surface and underground mining and construction projects can be found worldwide, built on a rock bed and surrounded by rock. Open pit mines are considered the primary sector for mineral production in the mining industry. The issue of slope stability is crucial for the economy and safety of open pit mines. Slope stability should be based on the determination of tectonic and lithological parameters and the determination of mine boundaries. It is illogical to allocate one slope for the entire walls of the mine, which are made of different materials and have different structural conditions. The purpose of slope stability analysis is to maintain a stable slope while mining activities continue. This research was conducted on slope stability analysis in the No. 4 Gol-e-Gohar mine in Sirjan. Geotechnical characteristics and necessary information for numerical modeling were obtained through mine visits, surveys, and tests on rock samples from exploratory boreholes. Based on two-dimensional modeling using PHASE 2D software, the CSFH behavior model (cohesion softening - friction hardening) for the northern wall will enhance the overall strength of the rock mass. However, this behavior model is not suitable for medium and weak-quality rocks. For rocks with softening behavior, the CSFS behavior model (cohesion softening - friction softening) provides more realistic results. Furthermore, to investigate the effect of schistosity plates, transisotropic behavior parameters were determined based on direct cutting tests on schistosity surfaces, and stability analysis was conducted. It was concluded that the orientation of the Turq surfaces in schist layers has a significant effect on the strength of these layers, leading to larger displacement values than other models.

To accurately predict the advance of a tunnel excavated by the drilling and blasting method, various parameters related to the rock and the operational conditions of the project should be taken into account. In this paper, comprehensive model was developed a to investigate the effects of different parameters on the advancement of such a tunnel. To achieve this goal, we conducted a systematic study at the tailrace tunnel of the Azad Dam in Iran. Rock properties, including the rock mass rating (RMR) and tunneling quality index (Q), as well as operational conditions such as blasting specific charge (q) and tunnel face area (A), were measured to establish comprehensive datasets for prediction. A total of 86 tunneling data points were collected and considered in this study. A novel model was developed, combining multiple regression (MR) and rock engineering systems (RES), to estimate tunnel face advance. The RES coding method was improved by incorporating a multiple regression model. The proposed coding method creatively assesses the influencing parameters, providing the advantage of accommodating uncertainties in the RES analysis. It achieves this by modeling the relationship between the explanatory (independent) variables and response (dependent) variables, thereby quantifying the interaction matrix. To evaluate the accuracy of the proposed models for both MR and RES datasets, we used the coefficient of determination (R2), a significant statistical criterion. A comparison of the values predicted by the models demonstrated that RES offers a more suitable performance than MLR for predicting tunnel advance. Sensitivity analysis of the MR-RES models reveals that the effective parameters on tunnel advance, in descending order of influence, are RMR (35.62%), Q (28.6%), q (20.35%), and A (15.42%). This hybrid method can be developed in other field of engineering without human judgment and consider statistical background of the data.

The expansion of cities and urban areas has resulted in an increased demand for environmental and economic transport and services infrastructure. Tunneling, as one of the mankind engineering underground constructions, is taking place close to buried and surface structures such as gas, water, and wastewater pipelines. This paper reviews soil-pipe interaction behavior, tunneling-induced ground settlement, governing equations of soil-pipe settlement, the effects of tunnel depth, size, soil relative density, and volume loss on vertical and horizontal displacement, settlement, shear strain, dilation, pipe bending, and gap formation. A comprehensive literature review, analysis of published papers, and investigations were conducted to study the effect of various parameters on pipeline behavior. The results were obtained by studying the effect of tunneling on ground and pipeline settlement, soil-pipe interaction mechanism, and centrifuge physical modeling. The achieved results of investigations show that the settlement profile follows a Gaussian curve with a wider settlement trough in clay compared to sand. When the tunnel and pipeline are perpendicular to each other, maximum bending strain in the pipeline occurs and the pipeline settlement is symmetrical. The friction effect and formation of contraction and expansion zone leads to difference between soil volume loss near the surface and tunnel volume loss. When the pipe-soil relative stiffness increases, the pipe bending is less than the maximum soil bending. Also, ground settlement, shear strain, pipeline displacement and pipeline bending are greater in flexible pipes than in rigid pipelines. This is due to the low resistance of flexible pipelines against bending and settlement caused by tunnel excavation. Positive pipeline bending (downward) occurs near the tunnel axis, which is marked by sagging, but negative bending (upward) occurs at a distance from the tunnel axis, which is known as hogging.  In twin tunnels, by increasing the tunnel spacing the pipeline settlement profile changes from V-shape to U-shape and finally W-shape. Understanding soil-pipe interaction behavior, tunneling-induced ground settlement, and the effects of different parameters on displacement, strain field, settlement, pipe bending, and gap formation beneath pipelines is crucial for engineers evaluating pipeline behavior. Additionally, comprehending these issues can help designers make informed decisions during tunnel construction.