Soroush Mahdavian, Navid Rashidi, Ali Raeesi, Jamal Abdullahi,
Volume 19, Issue 1 (6-2025)
Abstract
Clay soils typically have low strength and a high swelling percentage. They are considered as problematic soils in Civil Engineering projects. This research study examined the effects of magnesium chloride (MgCl2) solution on the clay soil improvement through conducting laboratory experiments. The experimental program included Atterberg limits, compaction, swelling, unconfined compression strength (UCS) and Scanning Electron Microscopy (SEM) tests. Available clay soil in the Lab was mixed with MgCl2 solution at weight percentages of 3%, 5%, 7% and 10% Samples for the swelling and strength tests were made using thestatic compaction method. The moisture and dry unit weight of the prepared samples were the same as those of thecorresponding compaction curves. The strength test results showed that the final strengths of the samples with 3% MgCl₂ at 7-, 14-, and 28-day curing times were 1401, 2018, and 1848 kPa, respectively. The results also showed that a reduction in strength of the samples occurred with more than a 3% solution of MgCl₂. For samples with 10% MgCl2 solution, the strength decreased until 14 days of curing time, but increased thereafter. Additionally, the results indicated that the reduction in swelling percentage compared to natural soil was 4.95%, 3.98%, 2.8%, and 3.9% for samples with 3%, 5%, 7%, and 10% MgCl₂, respectively, showing that the reduction in swelling depends on the MgCl₂ percentage. Additionally, the SEM results showed that the improvement in the soil was due to chemical reactions between the soil and MgCl₂.
Mrs Roya Masoumipour, Dr. Saeed Mahdavi,
Volume 19, Issue 1 (6-2025)
Abstract
The Chador-Malu open-pit mine is faces complex challenges regarding the long-term stability of its slopes. These are directly influenced by time, environmental changes, and stresses induced by mining activities. Considering the existing evidence of potential future instability, displacement changes along the northern to eastern pit walls were analyzed over an 18-month period. Long-term wall displacements were measured using radar. Through back-analysis and three-dimensional numerical simulations, the equivalent creep behavior of the slopes was evaluated using the Maxwell creep model. After assessing the geomechanical parameters, the impact of three scenarios passage of time, bench widening, and pit deepening on slope stability was investigated under three horizontal-to-vertical stress ratios of 0.5, 1, and 1.5. The analysis results indicated that a horizontal-to-vertical stress ratio of 1.5 better matched the field observations. In the first scenario, a 50% increase in time led to over a 100% increase in displacement rates, indicating a rise in instability potential over time. In the second scenario, unloading the first two benches reduces the instability potential, due to an 18% reduction in uplift while unloading up to the eighth bench increased instability potential due to the reduction of weight at the slide’s toe and an increase in the average uplift. In the third scenario, pit deepening formed another sliding zone between the tenth and seventeenth benches.
Mohammad Reza Haddad Tehrani, Mehdi Talkhablou, Mohammad Reza Asef, Mehdi Ostad Hasan,
Volume 19, Issue 2 (10-2025)
Abstract
Complex carbonate reservoirs, such as the Asmari Formation, present challenges to the accurate determination of geomechanical parameters and effective stresses due to high lithological and structural heterogeneity. The objective of this study is to develop a comprehensive three-dimensional model of geomechanical parameters and effective stresses in the Kupal oil field. Well log, core, and seismic data were used, and three-dimensional modeling was performed using the Sequential Gaussian Simulation (SGS) method based on variogram analysis. The prevailing stress regime was validated using FMI logs and wellbore breakout analysis. Additionally, a one-at-a-time sensitivity analysis was conducted on key parameters, including static Young’s modulus, Poisson’s ratio, cohesion, internal friction angle, and pore pressure. Results indicate that the maximum vertical effective stress (σv) is 87 MPa and the maximum horizontal effective stress (σHmax) is 127 MPa. Analysis of wellbore imaging data confirms a normal faulting stress regime (σv>σHmax>σhmin) in the field. Stress concentration around minor faults was also identified. The model was validated against one-dimensional models achieving 88% agreement. The findings of this study can be applied to well design, gas injection, and reservoir stability assessment in the Kupal field.
Soroush Mahdavian, Ali Raeesi Estabragh, Shima Azadeh Ranjbar,
Volume 19, Issue 3 (12-2025)
Abstract
This research study investigated the impact of dimethyl phthalate (DMP) on the physical and mechanical properties of clay soil through experimental testing. Additionally, the impact of hydrated lime and magnesium oxide on improving the properties of clay soil was investigated. The contaminated soil was artificially produced in the laboratory. Natural and contaminated soils were mixed with the above agents at percentages of 5.0%, 10.0% and 15.0%, respectively. The experimental test programme for this study comprised: Atterberg limits, compaction, uniaxial compression tests (UCS) and scanning electron microscopy (SEM). Samples for the UCS tests, both with and without additives, were prepared using the static compaction method and tested at curing times of 7, 14 and 28 days. The results showed that, in general, the Atterberg limit, compaction parameter (maximum dry unit weight) and UCS values for the contaminated soil were lower than for the natural soil. The results also indicated a reduction in UCS values for a mixture of contaminated soil and 10% hydrated lime or magnesium oxide. A comparison of the final strength values of samples made from a mixture of contaminated soil and 10% hydrated lime or magnesium oxide showed that the strength was 34.4% and 63.8% lower than that of a mixture with 5% of these additives at the same curing time. The E50 values were calculated from the stress-strain curves of the different tests. Additionally, the SEM results showed that changes in the properties of the mixture prepared from these agents and natural or contaminated soil were due to a chemical reaction between the soil and the additives.
Reza Mohseni Afkham, Dr Mojtaba Bahaaddini, Dr Abbas Majdi,
Volume 19, Issue 3 (12-2025)
Abstract
Tensile strength is one of the most important mechanical properties of brittle materials and plays a decisive role in the stability of many civil and mining structures. The Brazilian test is the most common indirect method for determining tensile strength and is widely employed. In this test, it is generally assumed that a central tensile crack initiates and propagates along the loading axis. However, the actual fracture process in the Brazilian test remains a controversial issue, and using curved loading platens has been recommended to better concentrate tensile stresses at the center of specimen. This study investigated the influence of platen curvature on the estimated tensile strength and the fracture patterns. To this end, five types of platen with curvature ratios of 0, 0.50, 0.57, 0.67, and 0.80 were prepared. All tests were recorded using a high-speed camera to precisely capture the initiation and propagation of cracks. To minimize the effect of rock heterogeneity and obtain consistent results, synthetic specimens were used, and five samples were tested for each curvature ratio.The results indicated that increasing the platen curvature led to a higher estimated tensile strength. While the increase was negligible for curvature ratios up to 0.67, at the ratio of 0.80 the tensile strength was approximately 48% higher compared to 0.67. Analysis of fracture patterns revealed that at the curvature ratio of 0.80, the fracture mode shifted to an unstable and disturbed pattern, characterized by secondary shear cracks and the irregular propagation of the main crack.
Ms Solmaz Darsanj, Dr. Mehrdad Emami Tbrizi, Dr. Hassan Afshin,
Volume 19, Issue 4 (12-2025)
Abstract
Aeolian sands in arid and semi-arid regions are considered problematic due to their loose structure, low bearing capacity and difficulty in compacting them. Iran's dry climate and phenomena such as the desiccation of Lake Urmia have exacerbated the dispersion of saline sands. One common approach to mitigating these issues is chemical stabilization using additives such as cement. This study investigates the effect of stabilizing saline aeolian sands collected from the Lake Urmia basin using Type I Portland cement. Stabilized soil specimens with varying levels of salinity and cement content were prepared and subjected to unconfined compressive strength testing after a 7-day curing period. The results showed that increasing the cement content significantly improves compressive strength. Furthermore, the presence of salt in the soil samples did not hinder the stabilization process, but instead contributed to improved strength in the short term. These findings highlight the importance of considering the type and concentration of salts when designing stabilization treatments for saline granular soils in arid and semi-arid climates.
Masoud Khahanipour, Hossein Sarbaz,
Volume 19, Issue 4 (12-2025)
Abstract
This study aims to numerically analyze the axial force, shear force, and horizontal displacement in Tunnel B on the Pataveh-Dehdasht axis. The tunnel is part of a national project that was inaugurated in the summer of 2023. The project's technical specifications include 2.2 million cubic meters of earthwork, 2,100 meters of retaining walls, 110,000 tons of subbase and base layers, and 95,000 tons of asphalt. This study investigated the effect of tunnel lining thickness on shear force, axial force, and horizontal and vertical displacement using PLAXIS finite element software in a two-dimensional framework. Plane strain theory was employed with 15-node elements for modeling. The Mohr-Coulomb constitutive model, one of the fundamental stages in numerical analysis and a common model for tunnel excavation simulations, was applied to model the soil behavior of the study site. The results indicate that increasing the lining thickness reduces vertical and horizontal displacement at all points while increasing axial and shear forces. Maximum deformation occurs at the tunnel invert and minimum deformation occurs at the right sidewall of the tunnel. Increasing the lining thickness from 20 cm to 35 cm leads to a reduction of approximately 100% in tunnel floor settlement and a significant decrease in horizontal displacement exceeding 90% at certain points. These results demonstrate the importance of selecting an appropriate lining thickness for controlling deformations, enhancing load-bearing capacity, and improving the tunnel's seismic safety.
Dr Seyed Ali Asghari Pari,
Volume 19, Issue 5 (12-2025)
Abstract
This study investigates the effect of Soil-Water Characteristic Curve (SWCC) parameters on the slope stability of an earth dam under steady-state and rapid drawdown conditions. Given the importance of unsaturated soil behavior in earth dams, this research employs principles of unsaturated soil mechanics to analyze the influence of SWCC parameters on water flow rate and slope stability.The results indicate that parameters a and n positively enhance the flow rate, while an increase in parameter m reduces it. In slope stability analysis, parameters of SWCC showed negligible effects on the downstream slope stability, whereas an increase in m caused a slight reduction in the safety factor. Under rapid drawdown conditions, all parameters initially led to a decrease in the safety factor, but stability was restored after 10 days. Additionally, accounting for the unsaturated unit weight of the soil improved the safety factor in both steady-state and rapid drawdown scenarios. These findings highlight the critical role of unsaturated soil conditions in the design and stability analysis of earth dams.
Dr Ali Ghanbari, Dr Mohammad Nakhaee, Dr Saeed Kalani, Dr Hamidreza Azizi,
Volume 20, Issue 1 (6-2026)
Abstract
Land subsidence is a complex geotechnical hazard with profound impacts on environmental stability, infrastructure resilience, and socio-economic security. This research presents a systematic field-based assessment of subsidence manifestations across the Hashtgerd, Eshtehard, and Karaj plains in Alborz Province, based on extensive surveys conducted in spring and summer of 2025. Diagnostic indicators, including extensional and compressional ground fissures, localized structural deformations, wellhead displacements, large-scale surface cracks, and variations in groundwater levels, were systematically documented. The Hashtgerd plain, particularly the Saeidabad, Sepehr, and Najmabad areas, exhibited the highest density of subsidence evidence, including progressive surface settlement, widespread fissuring, and instability of near-surface strata. In the Eshtehard plain, structural cracking in school buildings, ground ruptures adjacent to transmission towers, and retaining wall failures were frequently observed. Deep surface fissures were also identified in the Fathabad region, which is located between Eshtehard and Buin Zahra. In contrast, despite significant groundwater withdrawal, field surveys in parts of the Karaj plain revealed no pronounced subsidence indicators. The findings highlight a strong spatial correlation between the severity of subsidence and geological heterogeneity and unregulated groundwater exploitation.The absence of smart metering systems in wells also contributed to this issue. This study underscores the urgent need for integrated monitoring frameworks, adaptive management strategies, and the application of advanced remote sensing technologies to mitigate and control the expansion of land subsidence in Alborz Province.
Salman Shamsoddini Motlagh, Saeed Mahdavi,
Volume 20, Issue 1 (6-2026)
Abstract
Due to the deepening of open-pit mines and associated environmental concerns, the current period has been termed the 'return to underground mining era'. One of the key factors in transitioning from open-pit to underground mining is designing crown pillars based on economic and technical considerations. Due to the uncertainties surrounding this research topic, the present study uses three-dimensional numerical simulations to investigate the interactive effects of geometric and geomechanical parameters on the behaviour of crown pillars during the transition to underground mining. Pillar behaviour was evaluated based on displacement magnitude and the volume of the plastic zone of the pillar. The results of the numerical simulation showed that geometric parameters play a much more significant role than rock mechanical properties. Of the geometric parameters, the pillar dimension index (the product of the pillar's thickness and span) and the crown pillar's span play a decisive role in controlling pillar behaviour. From a geomechanical perspective, within the range of variations considered in this research, the rock elastic modulus was identified as the parameter most influential on crown pillar behaviour. This parameter controls crown pillar behaviour at a critical value of 7 GPa. Crown pillar span was identified as the second most influential parameter and can predict crown pillar displacement with a correlation coefficient of 0.83. The pillar dimension index can estimate the plastic zone volume in the pillar with 20% accuracy.
Dr Seyed Ali Asghari Pari,
Volume 20, Issue 1 (6-2026)
Abstract
This study systematically compares probabilistic slope stability analyses performed using three widely used geotechnical engineering software packages: PLAXIS LE V21, GeoStudio 2024 (SLOPE/W module) and Slide2. Probabilistic analysis has emerged as an essential approach for quantifying uncertainties and calculating key metrics such as probability of failure and reliability index, given the critical importance of risk assessment and the inherent uncertainty in soil parameters. This research evaluates the capabilities, accuracy and efficiency of each software package, as well as their respective limitations, by performing identical analyses on three distinct scenarios (homogeneous soil, three-layered soil and pseudo-static conditions) while employing ten common limit equilibrium methods. The results show that, as the complexity of the problem increases, the factor of safety decreases while the probability of failure and discrepancies between the software packages increase. In the homogeneous scenario, the mean factor of safety ranges from 1.35 to 1.55, depending on the method selected, with a failure probability of 8–12%, and inter-software differences of less than 5%. In the layered scenario, the mean factor of safety decreases to 1.30–1.40, with inter-software discrepancies reaching approximately 15%. Under pseudo-static conditions, the mean factor of safety reduces by around 21% (to 1.15), the probability of failure rises to an average of 27%, and the inter-software discrepancies reach 25%. Advanced methods (Morgenstern-Price and Spencer) yield higher safety factors than simple methods (Ordinary/Fellenius). In terms of software performance, Plaxis LE offers the greatest accuracy in complex conditions, GeoStudio provides the most conservative estimates and, thanks to its advanced graphical tools, Slide2 is a suitable option for probabilistic risk assessment.
