https://www.irsrmjournal.ir/ JOURNAL OF ROCK MECHANICS en daily 1 Sun, 21 Dec 2025 00:00:00 +0330 Sun, 21 Dec 2025 00:00:00 +0330 https://www.irsrmjournal.ir/article_241200.html Presence of groundwater flow and surface water flow are among negative factors in construction of underground tunnels. Determining of the groundwater inflow rates into the tunnel is necessary for confronting of environmental problems and decreasing the risk of tunnel instabilities and falling. In this paper, the amount of inflow waters into the section 2 of Zagros tunnel, West Iran, have been estimated using analytical and Empirical methods. The results compared to the measured actual data of inflow water into the tunnel in different sections by consideration the abilities of the methods in prediction. It was revealed that the confidences of analytical and empirical methods are 14% and 69%, respectively. The results show that the hydraulic conductivities of the rock masses, as one of the key parameter in these methods, has an enormous effect on the accuracy of the predictions. Geological condition, hydrogeological properties of faulted and fractured zones, and the type of hydraulic conductivity test procedure could be caused to obtaining the incorrect hydraulic conductivity values and unreliable prediction of water inflow to the tunnel. The high ambiguities appear in fractured zones and cavities with high hydraulic conductivities. https://www.irsrmjournal.ir/article_241616.html This study develops and compares three machine learning models- Multiple Linear Regression (LMR), Artificial Neural Network (ANN), and Classification and Regression Tree (C&R Tree) - for predicting the Penetration Rate (PR) of a Tunnel Boring Machine (TBM). A comprehensive dataset of 161 field samples was compiled from 22.7 km of the Karaj Water Conveyance Tunnel, which is excavated through pyroclastic rock formations of the Alborz Mountains (Iran). This dataset incorporates key intact rock properties (UCS), rock mass characteristics (RQD, GSI, joint orientation), and critical TBM operational parameters (RPM, Fn, Fr). Model performance was evaluated using the coefficient of determination (R²) and mean absolute error (MAE). The ANN model was found to achieve the highest predictive accuracy (R² = 0.93, MAE = 0.02), followed by the C&R Tree model (R² = 0.80, MAE = 0.05), while the LMR model demonstrated lower performance (R² = 0.76, MAE = 0.07). Notably, the C&R Tree model offered superior interpretability, with the Geological Strength Index (GSI) identified as the most influential parameter. Furthermore, this model generated explicit decision rules, thereby elucidating the specific geological conditions associated with the minimum (2.38 m/h) and maximum (4.47 m/h) penetration rates observed in the terminal nodes. In summary, while the ANN model provides superior numerical precision, the C&R Tree model delivers interpretable insights that effectively bridge quantitative prediction and qualitative engineering analysis. The synergistic application of both approaches is thus proposed as a robust framework for optimizing TBM operations and enhancing tunneling productivity. https://www.irsrmjournal.ir/article_241377.html Tensile strength is a fundamental parameter in the analysis and design of mining and civil engineering structures. This property plays a pivotal role in assessing the stability of underground excavations and selecting appropriate materials for their stabilization. Due to the technical challenges associated with determining the direct tensile strength of brittle materials such as rock, standardized methods have been developed for the indirect estimation of this parameter. The objective of this research is the experimental comparison of four common indirect methods—the Brazilian test, Three-Point Bending test, Four-Point Bending test, and Point Load Index test—in determining the tensile strength of rock-like specimens. To this end, four mix designs yielding a spectrum of specimens ranging from fine-grained to coarse-grained were prepared and tested. The results indicated that for fine-grained specimens, the Point Load test yielded the lowest indirect tensile strength values, while the Brazilian test yielded the highest. Conversely, in coarse-grained specimens, while the Point Load test remained the lowest, the Three-Point Bending test exhibited the highest values. By presenting a controlled set of rock-like specimens and a direct comparative analysis between methods, this research provides a practical framework for selecting testing methods tailored to specific microstructural characteristics. The findings of this study can serve as a basis for developing conversion coefficients and improving indirect tensile strength determination methods for rock-like materials. https://www.irsrmjournal.ir/article_242636.html The oil industry and drilling operations are extremely important in today's life. One of the fundamental challenges in drilling oil wells is the issue of wellbore stability, which can sometimes lead to significant costs, including financial expenses as well as safety risks for personnel. The main concern of a drilling engineer is to maintain the well in safe conditions and prevent the collapse of the wellbore walls, which necessitates special attention to the drilling fluid program, casing design, and operational methods in drilling a well. This study examines the stability of oil well walls and the factors affecting it. To this end, using the logs derived from the formation under study, the formation data was first calculated, and then, using a geomechanical model of the formation in the ABAQUS finite element software, the wellbore stability was analyzed and the optimal drilling fluid weight was determined under various conditions. To this end, using ABAQUS software, a geomechanical model of a vertical well at a depth of 2600 to 2700 meters from the ground surface was simulated, and the optimal drilling mud pressure, at which no plastic zones form in the wellbore, was calculated. The lower limit of the optimal drilling mud pressure, determined through simulation in ABAQUS software, was calculated as 33.1 MPa, and the upper limit of the mud pressure was calculated as 121.7 MPa. The results indicate the efficiency of ABAQUS software in analyzing the stability of oil wells. https://www.irsrmjournal.ir/article_242648.html Tunnel excavation inevitably disturbs the in-situ stress state, leading to ground deformation and surface settlement that may affect adjacent structures and infrastructure. Conventional empirical and numerical approaches often struggle to capture the highly nonlinear and coupled interactions among geological conditions, excavation parameters, and structural responses. Soft computing techniques, especially hybrid neuro-fuzzy systems, offer an alternative data-driven strategy capable of modeling such complex relationships with improved adaptability and predictive performance. In this research, a database comprising 68 tunnel cases with similar excavation methods, geometrical characteristics, and ground conditions was compiled. The initial Fuzzy Inference System (FIS) structure was generated using subtractive clustering to automatically extract rule bases from the data. Gaussian membership functions were employed to ensure smooth transitions between fuzzy regions. The ANFIS model was trained in MATLAB using a hybrid learning algorithm that integrates least-squares estimation for consequent parameters and back-propagation for premise parameter tuning. The dataset was randomly divided into training, testing, and validation subsets to evaluate generalization capability. Model performance was assessed using statistical indices including mean error and correlation coefficient between predicted and measured settlements derived from convergence monitoring instruments. The developed ANFIS model demonstrated high predictive accuracy, with very low mean errors in both testing and validation phases and a strong correlation between predicted and observed settlement values. The results confirm the ability of the proposed framework to effectively model complex nonlinear relationships governing tunnel-induced deformation. The hybrid learning strategy contributed to stable convergence and minimized overfitting, while the rule-based fuzzy structure provided partial interpretability of the system behavior. Overall, the study indicates that ANFIS constitutes a reliable and efficient tool for intelligent settlement prediction and can support engineering decision-making in tunnel design, monitoring, and risk mitigation for projects with comparable geotechnical conditions. https://www.irsrmjournal.ir/article_243085.html The advancement of mechanized tunnels through fault zones is frequently accompanied by significant challenges arising from abrupt variations in rock mass geomechanical properties, including instability, collapses, groundwater inflow, squeezing, and reduced predictability of tunnel boring machine (TBM) performance. This study investigates the influence of fault zones on TBM performance using the Field Penetration Index (FPI) in conjunction with the torque-to-thrust ratio (Tq/Th). To this end, operational data from several major mechanized tunneling projects in Iran, including the Karaj, Ghomroud, Nowsoud, and Kerman water conveyance tunnels, were compiled and analyzed. FPI values were independently derived for faulted and non-faulted tunnel sections and compared through statistical analyses and normal distribution histograms. The results reveal that mean FPI values within fault zones are significantly lower than those in non-faulted sections, predominantly corresponding to very good (7 https://www.irsrmjournal.ir/article_243367.html This study investigates the effect of the cover-to-diameter ratio (H/D) on ground deformation and the response of the initial tunnel lining in layered clay soils using numerical modeling. The tunnel diameter was kept constant, and the H/D ratio was varied from 0.5 to 3.5 to simulate shallow to deep tunneling conditions. The analyses were performed using the finite element method with the Hardening Soil constitutive model. The excavation process and installation of the shotcrete primary lining were simulated in stages to realistically represent the construction sequence. The system response was evaluated using several indicators, including maximum surface settlement, settlement trough width, vertical and horizontal tunnel convergence, tunnel ovalization, and two-dimensional volume loss. In addition, settlement profiles were fitted using Peck’s Gaussian function to quantitatively evaluate settlement parameters. The results indicate that settlement behavior is strongly influenced by soil layering and stiffness variations. With increasing H/D within the stiffer upper layers, the settlement trough width decreased by about 30%, indicating a more concentrated settlement zone. As the tunnel entered a softer intermediate layer, the trough width increased by approximately 30%, reflecting greater lateral spreading of ground deformation. In contrast, the maximum surface settlement increased by about 30%, while the volume loss increased by more than 100%, indicating a greater development of the plastic zone with increasing cover. Tunnel structural response also intensified with increasing H/D: tunnel ovalization increased by about 75% and vertical convergence increased by about 85%, whereas horizontal convergence remained negligible. Radial displacement at the tunnel crown and invert increased by approximately 71% and 275%, respectively, indicating intensified deformation with increasing cover. Overall, the results demonstrate that increasing the H/D ratio amplifies both ground and tunnel deformations. Moreover, the presence of softer soil layers can significantly alter the settlement pattern by promoting wider settlement troughs. These findings highlight the importance of considering soil stratification and staged numerical analysis in the deformation-based design of urban tunnels. https://www.irsrmjournal.ir/article_243503.html Nowadays, tunnel excavation projects in urban environments have witnessed significant growth. Given the shallow depth of tunnels in such environments, they are mostly excavated inside the soft ground using the earth pressure balance machine (EPBM). Considering the high volume of grout injection in this type of excavation, using cement replacement materials can lower the cost and the environmental risks of two-component grout. One of these replacement materials is basalt powder (BP) obtained from basalt quarry stone cutting. The present study assesses the feasibility of using BP obtained from quarry stone cutting as a substitute for cement in the two-component backfilling grout. The results showed that BP can be used as a very suitable substitute for cement in the composition of the two-component grout. Based on the obtained results, the strength of the basalt-containing two-component grout is almost equal to that of the grout that contains cement without basalt. Also, the results obtained for the mix design with 30% BP are in good agreement with those of the mix design containing only cement in terms of bleeding, gelling time, and Marsh funnel tests. As a result, using industrial waste significantly reduces grouting costs and grout’s environmental risks.