Yönser Koşullarda Kayaların Dayanım ve Deformabilite Özelliklerinin Ultrasonik Dalga Hızından Tahminine Yönelik Görgül İlişkilerin Geliştirilmesi

Abstract

Rocks, particularly due to the presence of the weakness surfaces, such as bedding, schistosity, joint etc., generally have anisotropy in different degrees, and therefore, their mechanical properties are influenced by anisotropy and exhibit directional changes. Due to these anisotropy dependent differences, the strength and deformability properties of rocks are important properties which should be taken into consideration with their anisotropy conditions in the design stage of rock engineering applications. This situation has oriented the researchers to carry out studies on the estimation of strength and deformability properties using different methods. Due to the facts that it has relationships with intact rock meterial properties, can be easily determined in laboratory and is a nondestructive test, the use of ultra-sonic wave velocity (Vp) has became more popular. Although the relationships between the strength and deformability properties and ultrasonic wave velocities (Vp, Vs) of rocks have been investigated in detail, the number of studies in which the effect of anisotropy due to weakness planes have been considered, are considerably limited. Besides, these studies have been conducted on limited number of specimens and no empirical equation to estimate the relationships between the strength and deformability properties and P-wave velocity (Vp) based on anisotropy conditions, has been recommended. By considering this gap in literature, in this study, it was aimed to estimate the strength and deformability properties from Vp at different anisotropy angles (0°, 15°, 30°, 45°, 60°, 75° and 90°) using the specimens prepared from six rock types. For this purpose, uniaxial compressive strength (UCS), indirect Brasilian strength (σt), modulus of elasticity (E) and P-vawe velocity (Vp) tests were carried out. Based on the test results, types of anisotropy for UCS and variation of UCS, σt, E and Vp with respect to the anisotropy angle were assessed. In order to indirectly estimate UCS, σt and E, when rocks include inclined weakness planes, empricial relationships using Vp were suggested. Since the prediction performance of these relationships are not strong, multiple regression analyses were carried out and the prediction performance of these new relationships was assessed. In addition, the values predicted from these analyses were compared with those obtained from the experiments. The assesments indicated that these final empirical relationship with high coefficient of determination (R2= 0.89 and 0.97, respectively) well predict the UCS and σt from Vp for different anisotropy angles. Although the empirical equations developed for the estimation of modulus of elasticity has high R2 (0.98) value, according to the distribution of the estimated data around 1:1 line, its prediction performance is not well.