Geological Environment and Engineering
Amir Mahyar Azhdarpour; Mohammad Reza Nikudel; Mashalah Khamehchiyan
Abstract
The central Alborz structural-sedimentary area in the middle part of the Alborz Mountain Range has endured geological events from the Precambrian to the present era, and contains numerous geological structures and formations. Among these, sandstone formations also have a significant expansion. In this ...
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The central Alborz structural-sedimentary area in the middle part of the Alborz Mountain Range has endured geological events from the Precambrian to the present era, and contains numerous geological structures and formations. Among these, sandstone formations also have a significant expansion. In this research, 6 different sandstone formations were sampled in 2 locations and tested to determine their physical and mechanical characteristics. In general, in the sandstone formations of central Alborz, top quartzite has stronger mechanical parameters than other formations. Shemshak Formation has the lowest mechanical parameters among the selected formations. Based on regression analysis, the conversion factor of PLT, BST and CPI parameters to unconfined resistance or UCS showed 20.6, 6 and 20.40 respectively with R2s of 0.75, 0.90 and 0.78. In terms of the Cerchar Abrasivity Index (CAI) as an index that can show the amount of abrasion, top quartzite has the most abrasiveness, which is due to its lithological composition. This sandstone formation is placed in the category of stones with high abrasive ability, and Shemshak Formation has the lowest Cerchar index among the formations and is placed in the group of stones with extremely low abrasiveness.
Geological Environment and Engineering
Abbas Zolfaghari; Mashallah Khamehchiyan; Mohammad Reza Nikoodel; Abdollah Sohrabi-Bidar
Abstract
The combined effect of the number of joints, opening, type and thickness of filling on the amount of vibration caused by the propagation of waves in four identical dry limestone blocks with dimensions of 10*10*50 cm was studied. The maximum vibration of particles in intact and jointed rock blocks in ...
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The combined effect of the number of joints, opening, type and thickness of filling on the amount of vibration caused by the propagation of waves in four identical dry limestone blocks with dimensions of 10*10*50 cm was studied. The maximum vibration of particles in intact and jointed rock blocks in three perpendicular directions was recorded by a three-component geophone. In block number 1 with a joint in the middle of the block, the amount of joint opening was changed from 3-6-9-12-15-18-21 mm and the measurements were made for each amount of opening in two series. In the first series, the joint filled with clay was tested, and in the second series, the joint filled with sandy soil was tested. This series of tests were also performed on blocks No. 2 with two joints, Block No. 3 with three joints, and Block No. 4 with four joints. The results of the tests showed that the presence of joints in rock blocks reduced the maximum vibration of particles in all three directions with different proportions. The relationship between the increase in the joint index and the decrease in the maximum vibration of the particles is nonlinear.
Exploration and Mining
Shahram Ghasemi; Mashalah Khamehchiyan; Mohammad Reza Nikudel; Ahmad Zalooli
Abstract
Joints and cracks are an integral part of rock structures. When load applied to these structures, growth, and interaction of the cracks lead them to failure. This aspect is particularly crucial in cyclic loading because failure occurs at stress levels lower than the yield point due to the fatigue process. ...
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Joints and cracks are an integral part of rock structures. When load applied to these structures, growth, and interaction of the cracks lead them to failure. This aspect is particularly crucial in cyclic loading because failure occurs at stress levels lower than the yield point due to the fatigue process. This research aims to study the growth and interaction of the cracks in the fatigue process by the fluorescence thin section method. At first, different stages of fatigue for granite rock were determined, then samples loaded up to each stage. Later, the physical, mechanical, and crack properties of the samples were investigated. The results show that physical and mechanical properties declined by increasing the number of cycles. During the first stage of fatigue, crack initiated at a high rate, and in the second stage, the increasing rate descended, and energy mostly consumed to increase the length of the cracks. In the last staged, which is the failure stage, the rate of crack initiation increases again and forms a complicated network of cracks, which leads the sample to failure. Among the constituent minerals, feldspar exhibits the highest crack density, and biotite shows the lowest density of the cracks.