Linear Regression and Spearman Rank Correlation Analyses of P-wave Velocity (Vp) and Rock Quality Designation (RQD) of Karacadağ Volcanics, Southeast Türkiye

Year 2025, Volume: 12 Issue: 4, 344 - 352, 12.01.2026

Gülen Tunç , Nuray Alpaslan

https://doi.org/10.26650/ijegeo.1832011

Abstract

The importance of geotechnical and geophysical investigations is significant, not only for the physical properties of the soil but also for its lithological, physical, and geomechanical characteristics from an engineering perspective. In this study, linear regression and Spearman rank correlation analyses were performed between the P-wave velocity (Vp) obtained from seismic refraction measurements applied to the Karacadağ volcanites exposed in and around the city centre of Diyarbakır and the rock quality designation (RQD) obtained from core drilling. In regression analyses for Karacadağ volcanites exposed in the city centre of Diyarbakır, the regression analyses between RQD and Vp-wave velocity for Gravel-sized clay-bound block basalt+Basalt, which makes up all the soil units, resulted in R2=0. 9298 has been calculated. It was determined that there were linearly very strong relationships between RQD and P-wave velocity in all units. In Spearman's rank correlation analysis for the Karacadağ volcanites exposed in the Diyarbakır city centre, the Spearman's rank correlation (rs) results showed a significant strong relationship between RQD and Vp (r (47) = 0.97852, p< 0.0001). In geotechnical investigations, integrated applications where many parameters are evaluated using different methods are quite advantageous. It was observed that the seismic velocities obtained by geophysical methods for the units in the study area, the rock quality designation (RQD) determined within the scope of geotechnical analyses, and the P-wave velocity (Vp) results supported each other.

Keywords

Basalt , Karacadağ Volcanics , P-wave Velocity (Vp) , Rock Quality Designation (RQD) , Linear Regression Analysis , Spearman Rank Analysis

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