Estimation of Strength and Deformation Characteristics of Khondalite Rock Mass using Rock Quality Designation

Abstract

Rock Quality Designation (RQD) is a measure used in Geotechnical engineering to assess the strength and integrity of rock core samples obtained during drilling operations, typically in the context of mining, construction, or civil engineering projects. RQD provides valuable information about the extent of weathering, fracturing, and discontinuities in a rock mass. The RQD is calculated by measuring the total length of sound or intact rock core within a specific drill run and dividing it by the total length of the run. Since the estimation of strength and deformation properties of rock masses requires sophisticated equipment, it is proposed to find these parameters through RQD values using the available analytical solutions. The drill log details of an irrigation project of Andhra Pradesh state in India were collected from the water resources department to analyze the RQD values of rock samples at different locations. The variations in RQD values of Khondalite rock with respect to depth and lateral distance are compared among 15 borehole locations of average spacing 40 m each. The values of bearing capacity, unconfined compressive strength and deformation modulus of rock masses corresponding to different borehole locations and different depths were estimated through RQD values using the analytical equations. The results were compared with respect to lateral distance and depth. Based on the analyses conducted, it was concluded that the estimation of strength and deformation characteristics of rock masses can easily be predicted from the RQD values.