Rock mass characteristics of the Fagfog Quartzite along the Kalu Pandey Highway, Central Nepal Lesser Himalaya

Abstract

The Fagfog Quartzite, a prominent lithostratigraphic unit of the Upper Nawakot Group, Lesser Himalaya, is extensively exposed along the Kalu Pandey Highway, Central Nepal. Rock mass characterization was carried out at fifteen road-cut slope sites (F1–F15) using the Rock Mass Rating (RMR). Five parameters were systematically assessed: uniaxial compressive strength (UCS), Rock Quality Designation (RQD), discontinuity spacing, condition of discontinuities, and groundwater condition. RMR values ranged from 72 to 85, classifying the rock mass as Class II Good Rock at nine sites and Class I Very Good Rock at six sites. UCS ranged from 50 MPa to >200 MPa; RQD was uniformly excellent (89–100%). Three discontinuity sets trend NW–SE; discontinuity spacing (R3) and condition (R4) were the dominant controls on RMR variability. Groundwater was completely dry during dry-season fieldwork; monsoon-season conditions may reduce RMR by up to 8–10 points. The dataset provides a geotechnical baseline for the Fagfog Quartzite and supports future kinematic failure analysis and Slope Mass Rating (SMR) assessment for highway slope stability management.