Classification of Limestone Rock Masses Using Laboratory and Field P-wave Velocity by ArcGIS Fuzzy Overlay (AFO) (Case Study: Five Dam Sites in Zagros Mountains, Western Iran)

In this study, 18 seismic tomography profiles in limestone rock masses with a total length of 2450 meters were studied to find the relationship between P-wave velocity in field and laboratory (V_PField and V_PLab) and rock mass classifications (Q and Q_srm) in the Zagros mountains, western Iran. The results showed that the Q rock mass classification system and its modified system for sedimentary rock masses (Q_srm) were closely related to V_p parameters. In addition to the V_PField, K_P (V_PField/V_PLab) also showed a significant relationship with Q and Q_srm. The best multivariate equation between V_PField and K_P with Q_srm (R² = 0.70) was more reliable and had less error than the best between V_PField and K_P with Q (R² = 0.55). The reason for this was the status of the voids and some other rock mass properties such as bedding and structure of rock mass in calculating the Q_srm, which were neglected in calculating the Q index. Certainly, voids and many rock mass properties in the limestone were very effective in the amount of K_P and V_PField. Also, the development of models of ArcGIS fuzzy overlay (AFO) methods for prediction of Q_srm showed very interesting results because it was able to show stronger accuracy (R² = 0.89). In order to check the accuracy and errors of the obtained models, “Error%”, “Mean Absolute Percentage Error”, “Mean Absolute Deviation” and “Root Mean Square Error” indicators were used which showed the high-efficiency of the AFO model in estimation the Q_srm. According to the results of this study, it was proposed: in the studied calcareous rock masses, Q_srm classification can be a suitable substitute for Q classification.