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Effect of magnesium chloride solution on the improvement of a clay soil
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.

Long-term displacement analysis of the northeastern slope of the Chadormalu open-pit mine
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.

3D modeling to determine the geomechanical parameters of the Asmari reservoir and the principal stresses in one of the fields in southwestern Iran
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.

Effect of the Soil-Water Characteristic Curve (SWCC) parameters on the slope stability of an earth dam in steady state and rapid drawdown
Dr Seyed Ali Asghari Pari,
Volume 19, Issue 6 (12-2025)
Abstract
Various factors influence earth dams' stability and flow rate, including geometric characteristics, material permeability, and upstream water height. Understanding unsaturated soil behavior in earth dams is crucial, necessitating the application of unsaturated soil mechanics principles due to the complexities involved. 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. The findings reveal that SWCC parameters significantly influence water flow and slope stability. Additionally, considering unsaturated unit weight can improve slope stability under varying conditions.
 

Evaluation of Cement Performance in Urmia Lake Basin Stabilizing Saline Soils
Ms Solmaz Darsanj, Dr. Mehrdad Emami Tabrizi, Dr. Hassan Afshin,
Volume 19, Issue 6 (12-2025)
Abstract

Aeolian sands in arid and semi-arid regions are considered problematic soils due to their loose structure, low bearing capacity, and difficult compaction. The dry climatic conditions of Iran and phenomena such as the desiccation of Lake Urmia have intensified the dispersion of saline sands. One of the common approaches to mitigate 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 were prepared with varying levels of salinity and different cement contents, and were subjected to unconfined compressive strength testing after a curing period of 7 days. The results demonstrated that increasing the cement content significantly enhances compressive strength. Moreover, the presence of salt in the studied soil did not hinder the stabilization process; instead, it contributed to improved strength in the short term. These findings underscore the importance of considering both the type and concentration of salts when designing stabilization treatments for saline granular soils in arid and semi-arid climates.

 

Numerical analysis and investigation of axial force, shear force and horizontal displacement in underground structures
Masoud Khahanipour, Hossin Sarbaz,
Volume 19, Issue 6 (12-2025)
Abstract
The aim of this study is to numerically analyze the axial force, shear force, and horizontal displacement in the tunnel (Tunnel B on the Pataveh-Dehdasht axis). This tunnel is part of a national project, which was inaugurated and put into operation in the summer of 2023, with technical specifications including 2.2 million cubic meters of earthwork, construction of retaining walls with a total length of 2,100 meters, 110,000 tons of subbase and base layers, and 95,000 tons of asphalt.
In the present study, the effect of tunnel lining thickness on shear force, axial force, and both horizontal and vertical displacements was numerically investigated using the PLAXIS finite element software in a two-dimensional framework. Plane strain theory was employed with 15-node elements for modeling. For the surrounding soil, the Mohr-Coulomb constitutive model, which is one of the fundamental stages in numerical analysis and commonly used in most tunnel excavation simulations, was applied to model the soil behavior of the study site.
The results indicate that increasing the lining thickness reduces both vertical and horizontal displacements at all points, while axial and shear forces increase. The maximum deformation occurs at the tunnel invert, and the minimum occurs at the right-side wall of the tunnel. Increasing the lining thickness from 20 cm to 35 cm leads to an approximately 100% reduction in tunnel floor settlement and a significant decrease in horizontal displacement, exceeding 90% at certain points. The findings highlight that selecting an appropriate lining thickness plays a key role in controlling deformations, enhancing load-bearing capacity, and improving the seismic safety of the tunnel.
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Improvement behaviors a clay soil contaminated with dimethyl phthalate by magnesium oxide and hydrated lime as additives
Soroush Mahdavian, Ali Raeesi Estabragh, Shima Azadeh Ranjbar,
Volume 19, Issue 6 (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.

Experimental investigation on the effect of loading platen curvature on the failure patterns in the brazilian test
Reza Mohseni Afkham, Dr Mojtaba Bahaaddini, Dr Abbas Majdi,
Volume 19, Issue 6 (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.

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