Rock Mechanics
Vahab Sarfarazi; Lei Zhou; Hadi Haeri; Parastou Salehipour; Ali Elahi; Ali Moayer; Mohammad Fatehi Marji
Abstract
The mechanical behavior of rock-rock bolt interface considering the effects of indents’ shape and their number was numerically simulated based on discrete element method using the two-dimensional particle flow code. The conventional and standard uniaxial compressive and Brazilian tensile strengths ...
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The mechanical behavior of rock-rock bolt interface considering the effects of indents’ shape and their number was numerically simulated based on discrete element method using the two-dimensional particle flow code. The conventional and standard uniaxial compressive and Brazilian tensile strengths tests were used to calibrate the modelled samples with 100 cm 100 cm in dimension. The numerical models were prepared such that different indent shape and number were inserted in the cable bolts arrangements during the rock reinforcement process. The effects of confining pressure 3.7 MPa and different shear failure loads were modeled for the punch shear test of the concrete specimens. The results of this study showed that the dominant failure mode of the rock-cable bolt interface was of tensile mode and the shape and number of cable indents significantly affected the strength and mechanical behavior of the modelled samples. It has also been showed that the indent dimensions and number affected the shear strength of the interfaces.
F. Rastegar; H. R. Nejati; A. Ghazvinian; M. R. Hadei; A. Nazerigivi
Abstract
The tensile strength of rocks plays a noteworthy role in their failure mechanism, and its determination can be beneficial in optimizing the design of the rock structures. Schistose rocks due to their inherent anisotropy in different foliation directions show a diverse strength at each direction. The ...
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The tensile strength of rocks plays a noteworthy role in their failure mechanism, and its determination can be beneficial in optimizing the design of the rock structures. Schistose rocks due to their inherent anisotropy in different foliation directions show a diverse strength at each direction. The purpose of this work was to compare and assess the tensile strength of phyllite, which was obtained in direct and indirect tensile tests in different foliation directions. To this end, several phyllite specimens with different foliation angles (0º, 30º, 45º, 60º, and 90º) related to the loading axis (β) were prepared. Finally, the direct tensile test, diametrical and axial point load tests, Brazilian test, and Schmidt hammer test were conducted on 188 samples. The results of the experimental tests revealed that the maximum and minimum tensile strengths in direct tensile testing tension were directly related to the angles of 0º and 90º. Also it was observed that the Brazilian tensile strength overestimated the tensile strength. Furthermore, an exponential correlation was introduced between the direct tensile strength and the Brazilian tensile strength.
H. Fattahi
Abstract
The tensile strength (σt) of a rock plays an important role in the reliable construction of several civil structures such as dam foundations and types of tunnels and excavations. Determination of σt in the laboratory can be expensive, difficult, and time-consuming for certain projects. Due ...
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The tensile strength (σt) of a rock plays an important role in the reliable construction of several civil structures such as dam foundations and types of tunnels and excavations. Determination of σt in the laboratory can be expensive, difficult, and time-consuming for certain projects. Due to the difficulties associated with the experimental procedure, it is usually preferred that the σt is evaluated in an indirect way. For these reasons, in this work, the adaptive network-based fuzzy inference system (ANFIS) is used to build a prediction model for the indirect prediction of σt of sandstone rock samples from their physical properties. Two ANFIS models are implemented, i.e. ANFIS-subtractive clustering method (SCM) and ANFIS-fuzzy c-means clustering method (FCM). The ANFIS models are applied to the data available in the open source literature. In these models, the porosity, specific gravity, dry unit weight, and saturated unit weight are utilized as the input parameters, while the measured σt is the output parameter. The performance of the proposed predictive models is examined according to two performance indices, i.e. mean square error (MSE) and coefficient of determination (R2). The results obtained from this work indicate that ANFIS-SCM is a reliable method to predict σt with a high degree of accuracy.
Rock Mechanics
M. Hosseini
Abstract
Temperature has a significant role in many actions performed on rocks. An example would be the effect of temperature on rocks in the burial of nuclear waste, geothermal energy extraction, deep oil well drilling, and fires in tunnels. In addition, due to diurnal/nocturnal as well as seasonal temperature ...
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Temperature has a significant role in many actions performed on rocks. An example would be the effect of temperature on rocks in the burial of nuclear waste, geothermal energy extraction, deep oil well drilling, and fires in tunnels. In addition, due to diurnal/nocturnal as well as seasonal temperature variations, rocks undergo a process of heating and cooling. In the present work, the effect of temperature as well as heating and cooling cycles on the rock properties was studied. The utilized samples included tuff, andesite, and sandstone. In addition to natural samples, concrete was also studied in this research work. The aim of this work was to evaluate the effect of temperature on the tensile strength of rocks and the velocity of longitudinal waves in a single heating and cooling cycle of samples as well as evaluating the effect of the number of heating and cooling cycles on the tensile strength of rocks and the velocity of longitudinal waves. In order to investigate the effect of temperature on the tensile strength of rocks as well as the velocity of longitudinal waves in a single heating and cooling cycle, the samples were heated in a furnace. After cooling the samples, the Brazilian and the sound velocity tests were carried out on them. These tests were conducted at the three temperatures of 100, 200, and 300 °C. In order to examine the effect of the number of heating and cooling cycles on the tensile strength and the velocity of longitudinal waves, the samples were heated up to the temperature of 100 °C and then cooled down in order to reach the room temperature. In this case, the work was conducted in the three modes of 5, 10, and 15 cycles. The test results showed that the velocity of longitudinal waves and the tensile strength of samples decreased but their porosity increased. Reduction in the tensile strength varied in different rocks so that the greatest and lowest reduction in the tensile strength was observed in concrete and andesite, respectively.
