Journal of Engineering Geology

Analysis of slope instability mechanism due to unusual rainfall: a case study of talubin village landslides (north of Meyami)

Aliakbar Momeni

Following an unusual period of rainfall period at the end of the previous winter, several landslides occurred in Tolubin village in early spring 2019. These landslides resulted in the destruction of 12 houses as well as causingdamage to roads and gas transmission lines. This this research was therefore conducted to investigate the mechanism of these landslides. The study was comprised four main phases: a literature review, field investigations, laboratory studies, and a slope stability assessment using Slide 6.20 software. During the field surveys, landslide-prone profiles were identified, and both disturbed and undisturbed samples were collected. The disturbed samples were used for laboratory tests, including determining the grain size distribution, calculating the Atterberg limits, performing calcimetry, conducting X-ray diffraction (XRD) analysis, and carrying out scanning electron microscopy (SEM) analysis. Additionally, 27 undisturbed samples were prepared for direct shear tests under varying moisture conditions. Finally, stability analyses of the studied profiles were performed in Slide software under different moisture conditions, considering both static and quasi-static states, based on the geometric characteristics of the slopes and shear strength parameters (internal friction angle and cohesion).. The obtained safety factors indicated that all slopes were on the threshold of failure under saturated static conditions and would certainly fail under saturated quasi-static conditions. In conclusion, the high sensitivity of the slope’s marly materials to moisture variations and the unusual rainfall in February and March 2019 were identified as the primary factors contributing to these landslides.

Hydrochemical characterization and health risk assessment of groundwater contamination in birjand plain, eastern iran

Reza Jahanshahi

This study examines the hydrochemistry and contamination levels of groundwater resources in the urban area of Birjand in eastern Iran. Water quality was assessed and pollution sources were identified through sampling 22 wells, 12 qanats and 4 springs. The results showed that electrical conductivity varied from 300 to 8,000 µS/cm, while pH ranged from 7.23 to 8.71. According to the Piper diagram, the dominant hydrochemical facies were chloride, sulphate and bicarbonate types. In some of the samples, the nitrate concentration exceeded the permissible limit of 50 mg/L set by the World Health Organization, indicating the influence of urban wastewater and agricultural effluents. The ionic ratios reveal the influence of halite and gypsum dissolution processes, as well as ion exchange reactions, on the chemical composition of the water. A health risk assessment showed that, while most sources are within the safe range for adults, some wells and qanats pose a higher risk to infants and children. This study aims to provide a scientific framework for understanding the geochemical processes that control water quality, and to identify high-risk areas for the sustainable planning and management of groundwater resources in the Birjand plain.

Identify and explore the subsurface gypsum karst formations of the Masjed Soleyman Petrochemical site using geophysical and geotechnical methods

Mashalah Khamehchiyan

Over the past three decades, research into the factors influencing the development of gypsum karsts has become an active and growing area of study. The mechanically weak nature of gypsum, along with its rapid dissolution and deformability, contributes to the formation of gypsum karsts, voids, and caverns in regions where gypsum deposits are present. This process can significantly undermine geotechnical stability by reducing bearing capacity and increasing settlement. This issue is particularly critical in heavy industrial settings such as petrochemical facilities, where large storage tanks and other infrastructure are founded directly on the ground surface. Consequently, identifying and assessing these processes is essential for the design, construction, and maintenance of engineering projects. This study assesses subsurface gypsum karsts within the Masjed Soleyman Petrochemical site using an integrated geophysical and geotechnical approach. Ground Penetrating Radar (GPR) was employed across 24 profiles totaling 2,307 meters, also geotechnical data were obtained from 113 boreholes drilled to depths of 20–40 meters. Following data analysis, 32 occurrences of subsurface gypsum karsts were identified at depths ranging from 4 to 36 meters. Subsequently, surface water drainage patterns were analyzed and digitized from historical Corona satellite imagery (1968). In parallel, groundwater levels and flow direction maps were generated using data from electric probe depth finder measurements in boreholes. The integration of these datasets revealed that most gypsum karsts are concentrated in areas where groundwater tends to accumulate and flow. Finally, groundwater sampling and chemical analysis revealed an average sulfate concentration of approximately 1,480 ppm, indicative of a severe sulfate exposure environment.

Experimental investigation on the effect of loading platen curvature on the failure patterns in the brazilian test

Mojtaba Bahaaddini

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.

Improvement the behaviors of a clay soil contaminated with dimethyl phthalate by magnesium oxide and hydrated lime as additives

Ali Raeesi Estabragh

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.

Sabzkuh Tunnel Excavation and Its Interaction with Environment Hazards in the Zagros zone, Iran

Majid Taromi

The Sabzkuh Water Conveyance System was planned as an inter-basin water transfer project in the Sabzkuh region of the Chaharmahal and Bakhtiari province, a tributary of the Karun River. Initially, the project included a diversion dam, an open canal, and a tunnel. However, in the initial feasibility studies, the potential environmental risks to the Choghakhor lagoon, ecosystem and regional groundwater resources were not given sufficient consideration.Only due to land acquisition problems in the Chahartagh forest area, the tunnel route was changed and the channel was also removed. Consequently, the project was scaled down to comprise only a diversion dam and a 11-kilometre-long tunnel. This is while the geological and environmental risks of the project area were not fully investigated in the selection of the final route. After 484 meters of excavation, the Solaqan fault was encountered and a sudden inrush of water with a flow rate of 100 liters per second and the liquefaction of the excavation front caused the TBM to get stuck. Subsequently, the drainage of water caused the drying of the Aloqareh spring and the depletion of the Shirkoshteh spring, and negative environmental and social consequences for the region. To release the TBM, two side galleries were constructed and grouting and drainage were carried out. Ultimately, the tunnel excavation operation was stopped due to the problems that arose. The challenges that arose in this project indicate the need for a comprehensive study and planning in the selection of the route and TBM, as well as environmental, economic and social assessments at all stages and examining their interaction with each other.