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Effects of unreinforced /reinforced sand layers coupled with / without sand columns on bearing capacity – settlement of soft clay
Mahmood Reza Abdi, Mahdi Safdari Seh Gonbad, Hoshmand Tirandazi,
Volume 15, Issue 3 (12-2021)
Abstract
In current paper the effects of surface unreinforced / reinforced sand layers coupled with and without single and group sand columns on the bearing capacity – settlement behavior of soft clays has been investigated. In this regard behavior of soft clay, clay + unreinforced / reinforced sand layer, clay + single / group sand piles and clay + unreinforced / reinforced sand layer + single / group piles samples has been assessed. Geogrid was adopted as the reinforcement, a circular plate 5cm in diameter as the loading surface and C.B.R. apparatus as the loading system. Results show that employing unreinforced / reinforced sand layers at a settlement ratio of 5% improves bearing capacity by 4 t0 7 times the soft clay. Coupling the surface unreinforced / reinforced sand layers with single / group sand piles further increases the bearing capacity by 7 to 9 times that of soft clay.

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Investigation of geomechanical properties of rock units of the eastern tunnel of Pervadeh Tabas coal mine and presenting experimental relationship
Mohadeseh Sadeghi, Naser Hafezi Moghads, Mohammad Ghafoori, Mehrdad Amiri, Ali Bashari,
Volume 16, Issue 2 (9-2022)
Abstract
 The design of underground or terrestrial structures on the rock bed depends on the physical and mechanical properties. Considering the mining method in Tabas coal mine extraction method is long and destructive, the evaluation of the geomechanical properties of the rocks is more necessary. In this research, the characteristics of the rock units of the eastern tunnel No. 3 of Tabas coal Pervadeh mine were investigated. In this study, 3 samples of shale, sandstone and mudstone were examined.  Considering the importance of the subject in this research, new experimental relations have been proposed, and their application shows desirable results. In order to obtain geomechanical characteristics and empirical relationships, physical tests such as porosity, water absorption percentage, unit volume weight, and mechanical properties such as uniaxial compressive strength, point load index, Brazilian tensile strength, direct cutting test, durability and brittleness index were carried out. To achieve the desired objective, the most appropriate relationships are presented using the regression method. Statistical analysis shows good correlation between different parameters in shale, sandstone and mudstone samples.
 

Shear Strength Study of Sand Reinforced by Waste Concrete
Dr Masoud Amelsakhi, Eng Elham Tehrani,
Volume 17, Issue 4 (12-2023)
Abstract
This research is a laboratory study to improve the geotechnical properties of sandy soils. Concrete waste with a grain size of 1.2 to 1 inch was used for this purpose. The effect of using concrete waste at 0, 10, 20 and 30 weight percent on dry sandy soil in two loose and dense states was investigated. Based on the results of the direct cutting test, the addition of concrete waste has increased the shear strength and the internal friction angle of the soil; The loose samples made with ٪30 of concrete waste had the greatest effect, so adding ٪30 of concrete waste to loose sand increased the internal friction angle of the soil by ٪32 and the shear strength by ٪42 Similarly, adding ٪10 of concrete waste to dense sand increased the internal angle of friction of the soil by ٪4 and the shear strength by ٪6.

Examining the impact of Flat-Joint and Linear Parallel Bond behavioral models on Aghajari sandstone failure mechanism in PFC2D simulations
Eng. Mohammad Ijani, Dr. Ebrahim Rahimi, Dr. Vahab Sarfarazi, Dr. Ali Faghih,
Volume 18, Issue 4 (12-2024)
Abstract
Numerical modeling is an essential tool in engineering analysis, particularly within the fields of geoscience and geotechnics. The PFC2D software stands out in this field, using the Distinct Element Method (DEM) to simulate processes related to engineering geology and geotechnical assessment. This study focuses on the analysis and comparison of two common contact models: the Flat Joint Model (FJM) and the Linear Parallel Bond Model (LPBM). The Unconfined Compressive Strength (UCS) test is chosen as a the benchmark for calibrating and validating the PFC models. Sandstone samples for this study are taken from the Aghajari Formation located on the southern limb of the Madar Anticline. The results show that both contact models have a high ability to simulate the UCS in the calibration process. As this test is primarily used to calibrate the failure point (σc) and Young's modulus, the output values for both models are almost identical. However, the post-failure behavior in the stress-strain curves differs between the models, with the FJM demonstrating a more brittle response compared to the LPBM. The ability of the FJM model to simulate rough surfaces and material discontinuities allows for the representation of tensile cracking.

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