Excavability Assessment of Carbonate Rock Masses in the Tarhuna Area, Northwest Libya

Abstract

Effective assessment of rock mass excavatability is a mandatory requirement for the strategic planning and economic control of civil and mining engineering works such as road cuts, trenches, quarries and open excavation. This study presents an assessment of rock mass excavatability in the Tarhuna area, northwestern Libya, located southeast of Tripoli. The study’s main objective was to design excavation methods for rock masses and estimate their excavability using multiple established geoengineering classification systems.          The geology of the study area consists of the Sidi as sid Formation (the Ain Tobi Limestone and Yafrin Marl members). The methodology involved extensive field work, including the drilling of exploration boreholes. Laboratory testing was performed on rock samples to determine key geotechnical properties, including the Unconfined Compressive Strength (UCS), Point Load Index (Is), and core quality parameters such as Total Core Recovery (TCR), Solid Core Recovery (SCR), and Rock Quality Designation (RQD). Rock mass characterization was achieved through established systems, specifically the      Rock Mass Rating (RMR) and the Tunnelling Quality Index (Q-System).

Excavatability was assessed using the Franklin method, the Excavatability Index (N-Index) and the Rip ability Rating (RR). The results indicated that the rock masses in the Tarhuna area generally require “very hard ripping,” which suggests that heavy-duty machinery or pre-blasting techniques may be necessary to increase production and penetrate the rock mass economically.

The study also demonstrates empirical alignments between the rock mass classifications and excavability assessment methods, adopting an integrated, multi-methodological geoengineering approach yields a significantly more accurate, well-calibrated, and balanced assessment of rock mass excavatability.