Himalaya is a young mountain with complex geology, and the tunneling activity in various projects in Himalayas are suffered by diverse geological problems such as difficult terrain condition, thrust zones, shear zones, folded rock sequences etc. Squeezing rock conditions in tunnels are defined to occur due to shearing of the ground with an associated inward movement of the tunnel perimeter. The factors influencing squeezing conditions are complex. The initial state of stress is important, which is usually difficult to determine in poor quality rock, orientation of the rock structure and groundwater conditions are also important factors. Rock squeezing problems such as inward movement, invert healing, swelling of side walls, mild convergence, running ground condition and buckling of walls/crown has been experienced during tunneling through low strength rock (sandstone, mudstone, siltstone etc.) shear zones and faults containing considerable amount of non swelling clay. All these challenges may result in increased cost and extended completion period. Though it is not a welcoming situation, but there is a lot to learn from such condition. The experiences of Himalayan tunneling are briefly presented in the paper.
