Experiences and Challenges of Tunnelling

Tunneling through weak and jointed rock masses such as in the Himalayas is a challenging task for the planners, designers, engineers and the geologists because of high overburden, thickly vegetated surface, poor rocks and highly varying geology with the presence of numerous small and big shear zones, thrusts, faults, etc. Due to these reasons, tunneling problems such as squeezing ground condition, chimney formation, face collapse, water in rush, etc. have been faced in the past and are still being encountered.Failures and the problems may be regarded as challenges and opportunities for generating new knowledge base and thereby increasing self-reliance in tunneling. Accordingly, recent experience of (i) tunneling through the poor rocks experiencing the squeezing conditions, (ii) SRF rating in case of competent moderately jointed rock experiencing spalling and rock burst condition, (iii) tunnels under dynamic condition, (iv) the effect of rock type on bolt length and (v) the improvement in rock mass quality Q because of the grouting of full-column rock bolt grout are presented in the paper. The challenges of cost-effective grouting in water charged rocks and swelling ground and TBM tunneling in Himalayas are also briefly highlighted

Keywords:

Tunneling , Squeezing , Rock Burst , Dynamic Condition , Rock Bolt , Grouting , Water-in-rush