A new approach to the anisotropy classification based on curve length measurement method: a case study in Ürkmez dam site-İzmir, Türkiye

Abstract

Anisotropy affects the measurements of uniaxial compressive and tensile strengths due to the presence of the weakness planes such as schistosity and foliation surfaces. Such rocks have different anisotropy behavior. The requirement for a more sensitive anisotropy classification which takes into account more parameters in the analytical approach promoted this study. It is recommended that the length of the curve obtained from the relationship between the orientation angles of schistose planes of anisotropic rocks and the uniaxial compressive, and tensile strengths should be examined separately. Variations both for compressive and tensile strengths of anisotropic rocks at different schistose plane orientations were investigated by curve length measurement method. The proposed definition in this study is based on the curve length (arc length) of the quadratic polynomial that fits all the data. The curve length concept has been associated for the first time with the anisotropy behavior of rocks in this study. The length of the curve reflects the degree of anisotropy in rocks because it is a precisely computable parameter. The curve length is constant for any kind of anisotropic rock; accordingly, each rock with anisotropy will have a unique function of degree two. In addition, as the degree of curvature increases, the length of the curve and the effect of anisotropy on the schistose rocks also increase. The aforementioned feature allows the precise comparison of the curve lengths of different anisotropic rocks. In this study, a new anisotropy classification method was proposed for the determination of the degree of anisotropy of rocks based on the length of the curve and the difference of strength between σ_cmax and σ_cmin values of the curve. The concept of R_t ratio, which is the anisotropy ratio under the tension stress, was introduced for the first time and applied in this study. While the mean curve length for the phyllites was 92.64±0.64, this value for the schists was 90.23±0.14. Thus, it was understood that the effect of anisotropy on the phyllites is higher than that of the schists in terms of tensile strength. The mean decreases in strength in phyllites and schists were also determined as 86% and 70.2%, respectively.