M. H. Ghobadi, A Ghorbani, H Mohseni, Ali Uromeiea,
Volume 8, Issue 4 (3-2015)
Abstract
Knowing the engineering geological characteristics of carbonate formations is necessary for database. In this research, using petrological study and mechanical tests on 5 types of Ilam-Sarvak formations limestones in Khorramabad city, their engineering geological characteristics were determined and the relationship between physical and mechanical properties have been analyzed. IBM SPSS Statistics (version 19.0) software was used to determine the required relations. The relations have high correlations. Based on the studies on this of thin sections, rocks are characterszed as biomicrite. Limestones of Ilam-Sarvak formations have high hardening and low porosity. These rocks are in medium to high density, very resistant durability index, medium to high UCS and high point load strength category. The rocks are also impermeable. Based on the UCS, modulus ratio of the intact rock, the limestones are CM and CL. According to solubility test, the solution velocity constant was 1.39×10-6 m/s.
Reza Mohseni Afkham, Dr Mojtaba Bahaaddini, Dr Abbas Majdi,
Volume 19, Issue 6 (Accepted Articles 2025)
Abstract
Tensile strength is one of the most important mechanical properties of brittle materials and plays a decisive role in the stability of many civil and mining structures. The Brazilian test is the most common indirect method for determining tensile strength and is widely employed. In this test, it is generally assumed that a central tensile crack initiates and propagates along the loading axis. However, the actual fracture process in the Brazilian test remains a controversial issue, and using curved loading platens has been recommended to better concentrate tensile stresses at the center of specimen. This study investigated the influence of platen curvature on the estimated tensile strength and the fracture patterns. To this end, five types of platen with curvature ratios of 0, 0.50, 0.57, 0.67, and 0.80 were prepared. All tests were recorded using a high-speed camera to precisely capture the initiation and propagation of cracks. To minimize the effect of rock heterogeneity and obtain consistent results, synthetic specimens were used, and five samples were tested for each curvature ratio.The results indicated that increasing the platen curvature led to a higher estimated tensile strength. While the increase was negligible for curvature ratios up to 0.67, at the ratio of 0.80 the tensile strength was approximately 48% higher compared to 0.67. Analysis of fracture patterns revealed that at the curvature ratio of 0.80, the fracture mode shifted to an unstable and disturbed pattern, characterized by secondary shear cracks and the irregular propagation of the main crack.
