DefinePK

Abstract

The geotechnical properties of sedimentary rocks are fundamentally controlled by their petrographic characteristics, yet this relationship remains critically understudied for the Hisartang Formation in the tectonically complex Nizampur Basin, Pakistan. This study presents an integrated petrographic and geotechnical evaluation to bridge this knowledge gap. A comprehensive methodology involving field sampling, petrographic analysis, and a suite of standardized geotechnical tests (Unconfined Compressive Strength (UCS), Unconfined Tensile Strength (UTS), Point Load Test (PLT), Ultrasonic Pulse Velocity (UPV), Schmidt Hammer Test (SHT), specific gravity, porosity, and water absorption) was employed. Petrographic results reveal the sandstone as a mineralogically and texturally mature subarkose, dominated by quartz (84%) with minor feldspar (15%) and chert (1%). The fabric exhibits tightly packed, sub-rounded to rounded grains with sutured, concave-convex contacts and quartz overgrowths, indicating significant compaction and cementation during diagenesis. Geotechnically, the formation exhibits exceptional properties: low porosity (0.24%) and water absorption (0.12%), high Unconfined compressive strength (123 MPa), tensile strength (16 MPa), and high ultrasonic pulse velocity (5154 m/s). The analysis demonstrates a direct causal link between the quartz-dominated mineralogy, the compact, well-cemented fabric, and the superior mechanical strength. This study conclusively establishes that the Hisartang Formation is a highly competent engineering material, suitable for demanding applications like foundation rock and high-quality aggregate. The findings provide a crucial predictive model for infrastructure development in the region and underscore the necessity of petrographic analysis in geotechnical forecasting.
Keywords
Petrographic-Geotechnical Correlation, Hisartang Formation, Engineering Properties, Quartz, Nizampur Basin