Ahmad Jafari; Mohammad Farough Hosseini; Aref Alipour
Mohammad Farough Hosseini; Hossein Mahmoudi Dovvom Niasar; Morteza Ahmadi; Vahid Sa'ati
Abstract
Gotvand dam is a rock fill dam located in Khoozestan province in Iran on Karun River. It will be constructed on weak mudstone and layers of sandstone. These layers are intermittent of medium strength with uniaxial compressive strength of 15 and 25MPa respectively. Some regional factors as continuous ...
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Gotvand dam is a rock fill dam located in Khoozestan province in Iran on Karun River. It will be constructed on weak mudstone and layers of sandstone. These layers are intermittent of medium strength with uniaxial compressive strength of 15 and 25MPa respectively. Some regional factors as continuous unloading, caused by river flood washed off and horizontal tectonic loading have created a local anticline in the base of the dam. It is estimated that such deformation will last over the time. Therefore, in order to determine creep parameters assessing the time dependent behavior of the foundation rock during the life of the dam through numerical and analytical methods is inevitable. In this research, by conducting creep tests under constant loads the strain- time graphs were produced for the two rock types. Applying the Burger rheological model for both rocks, their creep parameters were determined. In order to validate the produced data numerical modeling was conducted. A comparison between the results of numerical modeling and laboratory tests showed that the difference between the two methods is less than 6%. Also the time required for both rocks to enter the tertiary creep was determined to be 40 days for sandstone under 17.72MPa and 35 days for mudstone under 7.8MPa of load.
Sajjad Haghir Chehreh Ghani; Ali Asghar Khodayari; Mohammad Farough Hosseini
Mohammad Farough Hosseini; Soroush Fouladchi; Mojtaba Ganji
Abstract
Wave propagation is used as an advanced tool of determining elastic properties of rocks. In spite of being cheap and non destructive tests of rock mechanics, due to its modernity method is not yet replacing the traditional dear and destructive tests. In order to pave ways of replacing this test and making ...
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Wave propagation is used as an advanced tool of determining elastic properties of rocks. In spite of being cheap and non destructive tests of rock mechanics, due to its modernity method is not yet replacing the traditional dear and destructive tests. In order to pave ways of replacing this test and making best use of it all effective factors of such method are to be assessed. One fundamental factor affecting the test result is the shape of the specimen tested. The existing standards do not seriously take the sample shape into consideration. It was pointed out elsewhere that in spite of popular taught elastic dynamic properties do vary seriously due to variation of sample shape (height to diameter ratio). As this fact was revealed for limestone in our previous investigation this assessment was extended to other types of rocks for the possibility of true judgment. Therefore, ultrasonic wave propagation tests were conducted on four various rock types with height to diameter ratio of 0.5 to 3. Analyzing of the test results showed that shear wave velocity and elastic dynamic constants are noticeably dependent on sample height/diameter ratio. The variation of height/diameter ratio from 0.5 to 3 caused the variation of shear wave velocity and Poisson’s ratio up to 70%, Elasticity modulus up to 160% and shear modulus up to 200% as follows in details:
Variation in shear wave velocity: Limestone, 24%; Siltstone, 70%; Green Tuff, 17% and Granodiorite, 20%.
Variation in dynamic elastic modulus: Limestone, 26%; Siltstone, 65%; Green Tuff, 73% and Granodiorite, 33%.
Variation in Poisson’s ratio: Limestone, 45%; Siltstone, 160%; Green Tuff, 20% and Granodiorite, 35%.
Variation in shear modulus: Limestone, 53%; Siltstone, 200; Green Tuff, 38% and Granodiorite, 45%.
It was also observed that the longitudinal wave velocity was not following the height/diameter ratio and showed no specific trend of variation.
As seen from the above details, the variation of modulai is much grater for siltstone in compares to the 3 other rocks. It is most likely that this obvious difference is due to inhomogenity of the siltstone texture which causes different behavior in this particular rock.