Mechanical properties of selected granitoids along the Karora hydropower project, Besham, Northern Pakistan: Insights from petrography and joint analysis

The stability of tunnel site depends upon the deformation behaviors surrounding rocks, including joint density, mineral composition, micro cracks, and grain boundaries. aim this study was to analyze mechanical properties Besham Complex in Northern Pakistan terms petrography analysis. complex is prone as it bounded by Main Mantle Thrust (MMT) north, Thakot fault (Tf) east, Swat block west. In area, observed at mesoscopic scale, while alteration grains fractures were determined a microscopic scale. Detailed petrographic representative samples from each station revealed that area dominantly composed granite, quartz syenite, monzonite, granodiorite, quartz-rich granitoid, monzogranite, alkali feldspar monzodiorite. Extensive field work performed determine volume (JV), which number joints per cubic meter recorded for set. rock quality designation (RQD) calculated through JV An RQD value <25% suggested most rocks are very poor quality, with values between 25% 50% quality. analysis dominant contents (55.6%), (27%), mica (17.4%). Petrographic control over surface established, suggesting abundant feldspar, coarse grain, anhedral subhedral shape, microcracks, minerals provide planes weakness thus reduce value. Therefore, some serious precautions supporting measurements, such shotcrete, bolts, metal mesh, steel arch supports, essential avoid severe geo-hazards during further excavation.