This study integrates detailed geological mapping, rock testing, and established squeeze-prediction methods to assess tunnel squeezing risk at the 69 MW Lawi hydropower project in Chitral, Pakistan. Fieldwork identified three dominant rock types (serpentinite, talc-schist, slate/phyllite) in a tectonic mélange zone; discontinuities were measured at 12 stations along the headrace alignment. Intact rock samples were tested for uniaxial compressive strength (UCS) and unit weight. Rock mass quality was quantified via RMR, Q, and GSI systems using the field measurements. Squeezing was then evaluated by empirical criteria of Singh et al. (1992) and Goel et al. (1995), and the Hoek–Marinos (2000) semi-analytical approach, with in-situ stress estimated from overburden and rock density. Serpentinite was strongest (mean UCS ≈ 59 MPa) and talc-carbonate schist weakest (≈ 15 MPa). Most sections had poor rock quality (RMR < 40, Q < 1, GSI < 35). Singh’s criterion predicted that 8 of 12 sections would squeeze (FS < 1), and Goel’s N–BH^0.1 chart flagged nine sections as moderate-to-severe squeezing. The Hoek–Marinos solution indicated extreme closures (> 10% strain) in the central high-overburden mélange zone and moderate closures elsewhere. These converging results highlight a high-risk segment (~ chainage 7 + 998 − 9 + 298 m, within sheared ultramafic/phyllitic rocks under ~ 800 to 1000 m cover). We conclude that vigorous deformation (squeezing) should be expected in these zones, necessitating ductile and deformable support systems. Recommendations include yielding steel sets with fiber-reinforced shotcrete, forepoling/spiling and tight excavation advance controls, and continuous convergence monitoring. These findings provide a geotechnical framework for tunneling in similar Himalayan mélange zone (Hindu Raj region).
