Shimla Tunnel Blocked by Landslide: A Reminder of Geotechnical Risks

On August 12, a landslide in the Chalaunthi area of Shimla, Himachal Pradesh, caused debris to crash down, sealing the entrance of an under-construction tunnel. The incident occurred during the construction of a four-lane road from Parwanoo to Shimla, specifically in the Kaithlighat to Dhalli section. Fortunately, there were no casualties, as workers and machinery had been evacuated just before the landslide intensified.

The 400-meter tunnel excavation likely altered in-situ stress, reducing the hill's shear strength and destabilizing the slope. This disruption triggered progressive failure along existing or newly formed fractures, ultimately leading to the collapse.

The situation at the site remains unstable, with the national highway near the Dhalli junction still at risk as falling stones continue to pose a threat. 

To prevent similar occurrences in the future, it is imperative that thorough geological studies be conducted before and during construction projects in such challenging terrains. Understanding the stability of hillsides, the impact of excavation, and potential triggers for landslides can significantly reduce the risk of these dangerous events. In this case, the ongoing stabilization efforts by the National Highway Authority must be closely monitored and enhanced to ensure the safety of the workers and the surrounding infrastructure.

You can watch the collapse video here.