This book addresses geotechnical challenges in seismic zones, tunnels, slopes, rock mechanics, while integrating fundamental studies, case analyses, and digital innovations. Papers examine fault reactivation from CO2 injection, seismic effects on tunnels, and surface rupture modeling, providing tools for hazard prediction and mitigation. Case studies from India and Nepal highlight adaptive construction with monitoring, reinforced supports, and geotechnical zonation in weak Himalayan strata. Rock mechanics studies explore creep, fracture growth, freeze-thaw effects, and thermo-mechanical behavior for stability and geothermal applications. Tunnel design and sequencing optimize support with steel fibers, bolts, and real-time monitoring. Contributions cover slope stability, foundation settlement, blast-induced fragmentation, and excavation safety. Ultrasonic monitoring, infrared thermography, and AI-driven modeling enhance predictive accuracy, advancing resilient, sustainable underground infrastructure.