The estimation of Brittleness indexes of Qom Formation sandstones in northern Hamedan using the ratio between point load index and porosity

Brittleness which is of great significance in rock engineering properties is one of the most important properties of rock. The evaluation of brittleness indexes is a helpful method for the estimation of rock brittleness. However, there is still much uncertainty about the relation between rock brittleness and rock failures (i.e. Hydraulic fracture, Rock blasting in coal mines and tunnels). This fact can be attributed to the lack of a concept of universally accepted brittleness and brittleness index. In this paper, the relationship between rock brittleness is investigated by using the ratio of point index to porosity (PMP) in the sandstones of the Qom Formation. In addition, the available estimation methods for the rock brittleness index are summarized and their application is briefly discussed. In order to estimate of brittleness index and the ratio of point load index, 15 blocks from Latgah sandstones in northern Hamedan have been selected. Lithological characteristics, physical and mechanical properties of these sandstones have been determined. The samples have been tested under point load strength index uniaxial compressive strength (UCS), and Brazilian tensile strength experimentals. Then, the ratio of point load index to porosity (PMP) has been calculated. To achieve the desired target, the most appropriate and meaningful relationships between brittleness rock and the ratio of point load index to porosity (PMP) have been presented by the regression method. The relationships between point load index, porosity, and brittleness indexes (B1, B2, B3, B4, and BI) have been evaluated by simple regression (SR) techniques using Minitab 16 software. The statistical analyses revealed the existence of powerful correlations between the ratio point load index to porosity (PMP) with brittleness indexes (B3, B4)in the dry state and also, the powerful correlations between the ratio point load index to porosity (PMP) with brittleness indexes (B1, B2) in the saturated state.