57 research outputs found
Finite element study of preliminary design of tunnel support based on RMR and Q-system
No full textThe main purpose of a tunnel design is to use the rock itself as the principal structural material with little disturbance during the excavation and to provide as little support system as possible. Therefore, the determination of geological and geotechnical conditions in a project area is necessary as to provide the preliminary design of support system. For purpose of this research, secondary data from an island in Singapore were collected. The assessment on the rock mass classification and tunnel support system has been carried out using Rock Mass Rating (RMR) and Q-Index (Q) systems. These two sets of support systems obtained from the RMR and the Q systems will be compared and analyzed using the numerical analysis of Phase2 software. The stress conditions and resulting deformations around the tunnel were monitored to identify the workability of the proposed support system. It was found that, at depth of 50m, the RMR support system appeared to be conservative. However, at the depth of 145m, where the stress is almost three times at which, the proposed of RMR support system provide a satisfactory result compared to the Q system. It is also appeared that total displacement of the tunnel boundary is quite sensitive to the UCSi value. Further parametric study should be carried out on other rock mass parameters to monitor the tunnel behavior
Verification of post failure behaviour of rock using closed-circuit servo-controlled testing machine
No full textThe analysis of the stress-strain curve is a fundamental aspect in the field of rock mechanics. Most rock masses are not intact but have discontinuities. It is important to study the stress-strain curve beyond the peak failure as to assess the characteristic of intact rock against non-intact rock. However, several difficulties arise in obtaining the complete stress-strain curve. Since most rocks exhibit brittle behaviour, they fail violently and uncontrollably when tested on conventional compression machines. In this study, two series of uniaxial compression test were performed on sandstone samples. The first test was conducted using a 2000 kN MaTest conventional compression testing machine and the results were compared with a 3000 kN Tinius Olsen servo-controlled testing machine. Based on the results obtained from sandstone samples, post-peak failure can be achieved by using the servo-controlled testing machine. Comparison between the modes of failure observed from the tests on both types of machines clearly show that violent fracture is not the intrinsic characteristic of the rock but due to the rapid release of strain energy from the loading machine
Evaluation of tensile strength of brazilian test under solid and ring disks using finite element analysis
No full textThe tensile strength of intact rock materials has been determined by indirect method more frequent than the direct method.
The most commonly used indirect method is Brazilian test. Stress and deformability undergo during the test reflected by
geometry shape of the samples with respect to the different diameter ratio. This study focuses on influence of geometry
shape in solid and ring disk with different diameter ratio on the stress distribution and deformations within sandstone
subjected to indirect tensile loading by Brazilian test. Then, the finite element method in RS2 software was utilised to
simulate and gain in depth understanding the behaviour of Brazilian test. The analysis shown that the maximum tensile
strength in a ring disk with diameter ratio of 0.1 is three times higher than in solid disk. Meanwhile, as the diameter
ratio of ring disk increases, it produces lower tensile strength. The numerical simulation also has successfully illustrated
the shear failure which observed near the loading platen of solid disk during Brazilian test. The finite element analysis
utilised in this research has successfully enables the stress distribution and deformation behaviour of the rock under
tension to be studied closel
Evaluation of tensile strength of Brazilian test under solid and ring disks using finite element analysis
No full textThe tensile strength of intact rock materials has been determined by indirect method more frequent than the direct method. The most commonly used indirect method is Brazilian test. Stress and deformability undergo during the test reflected by geometry shape of the samples with respect to the different diameter ratio. This study focuses on influence of geometry shape in solid and ring disk with different diameter ratio on the stress distribution and deformations within sandstone subjected to indirect tensile loading by Brazilian test. Then, the finite element method in RS2 software was utilised to simulate and gain in depth understanding the behaviour of Brazilian test. The analysis shown that the maximum tensile strength in a ring disk with diameter ratio of 0.1 is three times higher than in solid disk. Meanwhile, as the diameter ratio of ring disk increases, it produces lower tensile strength. The numerical simulation also has successfully illustrated the shear failure which observed near the loading platen of solid disk during Brazilian test. The finite element analysis utilised in this research has successfully enables the stress distribution and deformation behaviour of the rock under tension to be studied closely
A study on stress-strain behaviour of granite and sandstone using closed-circuit servo-controlled testing machine
Get PDFThe objective of this study is to adopt a fundamental approach towards understanding the behaviour of granite and sandstone under uniaxial compression. The study is based on the complete stress-strain curve that represents the rock deformation under loading at a constant strain rate. Indeed, the complete stress-strain curve covers the behaviour of rock both at pre- and post-peak failure phases. To obtain the curve, the compression test need to be carried out using closed-circuit servo-controlled testing machine, or machine of high stiffness. In this study, a series of unaxial compressive tests on samples of granite and sandstone were undertaken using 3000 kN Tinius Olsen servo-controlled testing machine. Based on the complete stress-strain curves obtained, the deformation behaviour for both rock types are compared. Parameters being compared include peak strength, strain at failure and deformational behaviour at pre- and post-peak stages. Study on post failure behaviour of rock is particularly important in designing excavation, where rock materials may have been highly fractured or display certain degree of failure
Boundary condition considering shear force applied on flat loading platen for brazilian test
Get PDFIn general, the method used to obtain the tensile strength from a Brazilian test depends on the elastic theory for a pair of concentrated forces. However, the contact areas between the specimen and loading platens are observed in experiments. Several attempts have been tried for the boundary conditions in modeling of an isotropic or orthotropic circular disk in the Brazilian test. The forces in only the normal direction to the loading platen or specimen have been dealt with in most of these models. Therefore, a dent in the contact area between specimen and loading platens is observed in numerical results from most models. However, no dents have ever been observed in experiments using loading platens. In this study, not only normal loads but also shear loads on the loading platens are adopted as boundary conditions. The depth of the resulting dent from the present model is smaller than those seen in previous studies. In addition, huge tensile stresses are observed near both edges of the contact area in the present model. Furthermore, cracks are also observed near both edges in experiments. In brittle materials, cracks are caused by tensile stress. Therefore, the accuracy of calculations is expected to be improved using the present model for Brazilian tests
Technical visit to KVMRT Line 2 - V207 mined tunnel site
Get PDFLink to publisher’s homepage at https://www.myiem.org.my
Effects of quarry blasting towards the residential area at Kangkar Pulai, Johor, Malaysia
Get PDFThe drill and blast technique have been widely used recently due to demand for natural building materials like rock aggregates. However, the intensity of blasting effects has been questioned on its validity towards the nearby residential areas. In this study, the blasting effects from Quarry A and B has been assessed based on constant location of the residential areas (Taman Pulai Hijauan and Taman Bandar Baru Kangkar Pulai, respectively) using the empirical formulations only. The blasting effects are highly dependent on the maximum instantaneous charge in blast holes (Q) which are dependent on parameters like number of blast holes, charge per column, Powder Factor and number of blast per delay. This study was able to show that with an increase of the independent variables, the Q value rises significantly. The average Q value from Quarry A (181.07 kg) was slightly higher than Quarry B (180.22 kg). The correlations made for each quarry showed that Quarry A had a better regression line with lower standard error due to the high number of blast data obtained during the monitoring period of about 1 year and 8 months. Meanwhile, the impact assessments showed higher PPV (Peak Particle Velocity) value at higher Q holding blast holes in Quarry A compared to Quarry B and decreases with increasing distance. The similar relationship was observed for the air blast assessments. Yet, all of the blasts produced are relatively within safe limits which are less than 5 mm/s Mineral & Geosciences Department (JMG) and less than 125 dBL United States Bureau of Mining (USBM). Thus, extra precaution can be taken by estimating the suitable Q value such as A (97.66 kg) and B (271.68 to 495.01 kg) to maintain safe blasting operations and prevent damages to the nearby residential areas
Modeling for Distribution of Compressive Stress from Loading Platens in Diametrical Compression Test
No full textDiametrical Compression test is one of indirect tests to investigate the tensile strength of brittle materials. This test is spread because of easiness to perform. However, results from this test are not stable. Traditionally, calculations for this test are performed under a pair of opposite concentrated loading on the diameter of specimen. However, contact areas appear just before fracture of specimen in the fact and the stress distribution from loading platens is not obvious. It seems be one of reasons why the result from this test is not stable. In this study, the attempt to establish the modeling for distribution on loading platens in the diametrical compression test is shown. The aim of this modeling is to calculate stresses and displacement of specimen using complex stress function by Lekhnitskii. Therefore, this model is expanded in Fourier expansion. Accuracy of calculation using Fourier expansion depends on the number of terms. Therefore, the influence of contact area and number of terms to accuracy is also discussed
Stress Distribution in Specimen for Diametrical Compression Test under Some Boundary Conditions
No full textDiametrical Compression test is one of indirect tests to investigate the tensile strength of brittle materials. This test is spread because of easiness to perform. However, results from this test are not stable. Traditionally, calculations for diametrical compression test are performed under a pair of opposite concentrated load on the diameter of specimen. In the fact, contact areas are appears just before fracture of specimen and the stress distribution from loading platens is not obvious. It seems one of reasons why the result from this test is not stable. Several stress distributions between contact area and specimen have been proposed and stresses and strains have been calculated as theoretical results or analytical result in previous studies. In this study, the stress distribution that consists of uniform loading and cosine curve shaped loading is proposed and used for theoretical solution. Furthermore, results from this study are compared with results from previous studies
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