strength measurement of rock requires testing that must be carried out on test specimens with particular sizes in order to fulfill testing standards or suggested methods. Often, the coring process breaks up the weaker core pieces, and they are too small to be used in either index tests or conventional strength tests such as point load index (Is) and Brazilian Tensile strength (BTS). One of the index tests to indirectly determine the rock strength is the block punch index (BPI) test, which requires flat disc specimens without special treatment. This study aimed to evaluate the applicability of the BPI test for predicting the uniaxial compressive strength (UCS), BTS and IS of the sandstones by empirical equations. Also, we have compared the performance of the BPI and IS for predicting the UCS and BTS. It was experimentally shown that BPI is a reliable method for predicting the UCS, BTS and Is of the sandstones under study. Moreover, the results indicate that BPI could be utilized with same importance as Is for predicting the UCS, while predicting the BTS by Is appears to be more reliable than BPI.

Nowadays, the need to enhance the exploitation of hydrocarbon resources due to importance and increase in the rate of consumption of this material is more crucial than ever. On the other hand, the rock formations with low effective porosity, which are considered as hydrocarbon reservoirs prevented to have a suitable productivity of these reservoirs. Hydraulic fracturing is known as a process of initiation and propagation of fractures caused by fluid injection into the part of the boreholes in rock formations, which has an important role in increasing of the exploitation of hydrocarbon reservoirs with low efficiency. Initiation and propagation fractures have a high dependency to the parameters and properties of reservoir rocks. Among these parameters can mention, such as rock material, rock Tensile strength, pore pressure and etc. Importance Tensile strength of rock for predicting the breakdown pressure of hydraulic fracturing test is remarkable and this parameter is a function of lithology of reservoir rock. Hence, in this study with sampling at typical section of Asmari formation, evaluation of breakdown pressure parameter as a function of rock Tensile strength and lithology parameters has been paid. The ratio of hydraulic fracturing Tensile strength to Brazilian test Tensile strength and Point load test allows prediction of the Tensile strength and is an important parameter for simulation of hydraulic fracturing test results. Comparison of these ratios shows that the Tensile strength parameter is dependent on the test method. Rock Tensile strength that obtained from hydraulic fracturing test is 20.08 MPa and proportion between Tensile strength of hydraulic fracturing test to Brazilian test is equal to 2.35. Slight differences in the distribution of data and regression coefficient 0.9 are due to the small karst cavities, relatively low porosity and intragranular voids because of fossils in the rock structure. All evidences, including the results of physical and mechanical properties reveal the influence of lithology on the results of Tensile strength obtained from hydraulic fracturing test.

Treating soil with cement and zeolite is widely used in soil stabilization. This research intends to quantify the impact of cement and zeolite contents, porosity index, and voids/cement ratio on zeolite cemented sands by the splitting Tensile strength ( t) assessment. The approach of splitting Tensile tests using specimens by di erent zeolite replacement percentages was followed. Results indicated that cement was replaced by zeolite at optimum proportion of 30%. Then, improved values of  t by the e ect of zeolite and cement chemical properties in the cement sand specimens were attained. Zeolite can have a more signi cant e ect on a compacted mixture if its cement content and porosity increase. In this paper, it is shown that for the zeolite cemented sands,  t increases by increase in cement content (C) and reduction in porosity (n); and a power function is welladapted to  t both  t 􀀀 C and  t 􀀀 n. Afterwards, good correlations are obtained between voids/cement ratio (n=c) and the splitting Tensile strength ( t) of the sand-zeolite-cement studied. Finally, based on a number of input variables, namely, porosity (n), replacement of cement by zeolite (Z), and cement content (C), considering the regression approach, an equation is suggested to predict  t. Moreover, it is shown that the evolved equation could successfully predict the Tensile strength.

The Tensile strength of the anisotropic rock-like material specimens is meastred directly in the laboratory using a new device converting the compressive loading to that of the Tensile before the rock breakage. The specially prepared concrete slabs of dimensions 19 cm * 15 cm * 15 cm with a central hole of 7. 5 cm in diameter are tested experimentaly. The specimens are located in the compressive-to-Tensile load converting device, and tested under a compressive loading rate of 0. 02 MPa/s by the universal testing machine. The cubic slab samples are made in three different configurations to have the directions of 0° , 45° , and-45° with respect to the applied loading direction. In order to compare the direct Tensile strength of the concrete samples with that of the indirect measuring tests, some Brazilian tests are also carried out on the concrete disc specimens prepared in the laboratory. By comparing the direct and indirect testing results of the concrete Tensile strength, it can be concluded that the direct Tensile strength values are somewhat lower than those of the indirect ones. The Tensile strength values for the three different configurations of the concrete specimens are nearly the same.