Minimising Delays: Key issues and challenges faced by tunnelling contractors

Key issues and challenges faced by tunnelling contractors

While significant progress has been made in the Indian tunnelling sector in recent times, several issues continue to impede growth. Three key issues – geological complexities, poor contracting practices and safety issues – plague project implementation. While the industry can mitigate the latter two risks by adopting available best practices, geological complexities are harder to address, and this can be done only to an extent.

Geological complexities

Geologies impact almost every aspect of a tunnelling project, from conception to commissioning. Most tunnelling projects in India face significant issues arising from geological surprises and inadequate investigations. Issues such as thrust and shear tectonic zones, hot water springs or thermal zones, saturated strata consisting of lake and terrace deposits, and trapped methane gas pose significant challenges to tunnel contractors.

Therefore, detailed geological investigations are needed to determine the construction methodology and equipment requirement for projects. However, in their haste to issue tenders, developers do not undertake such geological investigations properly. Instead, they usually rely on surface geological mapping to interpret the region’s geology. In this case, unexpected geological complexities can impose huge financial risks and time delays on projects, resulting in disputes, improper tunnel alignment with a very low cover zone, non-availability of quarry for aggregates, and improper assessment of bridges/roads to transport heavy equipment to project sites. In India, such problems have usually been seen in hydropower, water supply and sewerage tunnel projects.

Deficiencies in contract documents and contracting practices

Another key issue in executing tunnel projects is the weak integrity of contract documents and practices. Ambiguous contracts are often the reason for disputes in tunnelling projects. For instance, roles and responsibilities and risk sharing among contract parties are often not clearly defined in the documents. Further, there is a lack of clarity on the methodology to be used for working out rates for extra items and for deviations in design or construction requirements. Even though dispute resolution procedures are laid down in contracts, the institutional arrangements in place to handle such disputes are usually weak. In India, such contractual issues have been typically observed in hydropower projects. Several projects in the sector have been delayed by five-seven years on average owing to such contractual issues.

Safety concerns

India does not have any guidelines or specifications for ensuring safety in construction and maintenance works of tunnel projects. There have been several cases where safety concerns have become a key reason for delays in project execution, often also causing loss of life. For instance, the accumulation of methane gas during the construction of the Loktak hydel project in Manipur led to explosions, impacting worker safety.

Such issues lead to loss of project momentum and make it difficult to ensure adequate manpower for projects. Further, compensation for accidents is not commensurate with the risks associated with these projects, adding to the difficulties in hiring workers.

Tunnel contractors thus need to undertake several measures to mitigate safety risks in tunnelling projects. They need to plan their excavation methodology – full face, heading-benching, multi-drift – depending on rock conditions, decide whether to pull back or advance, based on the stand-up time of the rock; provide design support at the earliest; monitor the tunnel profile post supports using instruments like extenso meters, bolts for convergence measurement and roof settlement measuring apparatus, etc; and redesign the excavation methodology and tunnel support or provide additional support if the need arises. At the same time, they also need to focus on ensuring adequate ventilation and air quality inside tunnels. Underground illumination during tunnelling works and the provision of safety gear such as helmets, protective clothing and glasses, etc., should be ensured. Monitoring safety levels, recording accidents, and undertaking periodic safety reviews/audits and preventive actions are a must.


Tunnelling projects in India are riddled with sector-specific challenges of heightened safety risks and geological uncertainties. Several projects have faced the brunt of these risks, resulting in project delays, cost escalations, loss of lives, and enhanced financial burdens. At the same time, the poor quality of enforcement contracts in the country, coupled with weak institutional mechanisms to deal with contract disputes, add to the contractor’s woes. Thus, appropriate measures need to be undertaken by project developers, tunnel contractors and appropriate government departments to mitigate such risks. Addressing these risks is expected to spur growth in the tunnelling sector.