A new classification system for evaluating rock penetrability

This paper presents a new classification system called the Rock Penetrability index (RPi). An evaluation model based on the fuzzy Delphi analytic hierarchy process (FDAHP) has been used for estimation of penetrability and drillability of rocks. For this purpose, five parameters of the rock material, including uniaxial compressive strength, Schimazek's F-abrasivity, mean Moh's hardness, texture and grain size and Young's modulus have been investigated and rated. In the RPi system, a number from 10.25 to 100 can be assigned to each rock, with higher values corresponding to greater ease of drilling and penetration into rock. Based on the RPi classification, rocks are classified into five modes from the view point of penetrability: very poor, poor, medium, good and very good.