Discontinuity-Induced Partial Instability in Markundi Hills, Sonbhadra, Uttar Pradesh, India.

State Highway-05A in Northern India, connects the states of Chhattisgarh, Madhya Pradesh, Uttar Pradesh, and Jharkhand. In Uttar Pradesh, it passes through steep and rugged Markundi Hill, composed of highly jointed sandstone. The current study examines road-cut slopes at six locations to quantify the instability mechanism and slope health. Detailed field and laboratory investigations were combined to ascertain the structural, petrographic, and strength attributes of the rock. Afterwards, data was collated to characterise the rockmass behaviour through widely accepted classification schemes, viz., geological strength index (GSI), Q-slope, rock mass rating (RMR), slope mass rating (SMR), and modified global slope performance index (modified GSPI). The value ranges provided by various empirical classifications are 40–62 (RMR), 39.61–58.46 (SMR) and modified 44.57–52.57 (GSPI). For structural stability, kinematic analysis was conducted. According to RMR, five locations fall in fair and one in poor rockmass classes. SMR suggest all locations are partially stable. Eventually, a novel approach for finding the ratings of GSPI is also introduced in the present work, allowing more comprehensive discontinuity characteristics incorporation. The new approach brings GSPI and SMR to the same scale, making it easy to compare the two. GSPI yields that all the locations have high chances of local bench failures. Compared to other approaches, GSPI predicts a wide range of instabilities and should be used alone or in conjunction with other systems for slope stability assessment. [ABSTRACT FROM AUTHOR]