Role of Technology in Managing Geological Uncertainties in Tunnelling

Colonel Parikshit Mehra, Tunnel Expert, emphasizes the critical role of technology in managing geological uncertainties and advocates integrating dynamic monitoring systems and data analysis to optimize tunnel support systems and ensure safety.
Integrating technology into tunnelling is crucial due to the many unknowns encountered underground. Engineers can only address these uncertainties by gathering data. This data comes from thorough exploration conducted with the right tools and techniques. During the actual tunnelling process, dynamic inputs are essential. A deep tunnel is essentially a circular opening in a converging plate. To manage this convergence, we use devices like 3D monitoring targets to measure deformation.
Processing data from these targets, along with extensometers, piezometers, and other inputs about water conditions, helps in understanding how excavation will impact the project. IoT technology plays a key role here. By combining and analyzing this data, geotechnical engineers on-site can make informed decisions about blast designs, excavation sizes, and support requirements. This helps in optimizing support structures and controlling costs.
Without dynamic technology inputs, we often resort to templated support systems, leading to either over-supporting or under-supporting rock formations. This results in time delays and increased costs due to the need for later reprofiling. Effective use of technology and automation can improve the accuracy of support systems and reduce delays.

All stakeholders, including contractors, authority engineers, and clients, need to be aware of and participate in the process. Clients, in particular, must be well-informed about technical aspects to ensure that appropriate technology is integrated from the planning stage. This collaborative approach is vital for implementing a technically robust project.
Regarding the Silkyara tunnel accident, a key issue was the lack of a comprehensive DPR and an inadequate contract. The DPR lacked critical data about the rocks, and the lump-sum EPC contract did not incentivize the contractor to provide adequate supports. Contractors often cut costs due to financial constraints, leading to insufficient support in the tunnel.
To prevent such issues, we need better DPRs and contracts that ensure tunnel supports are detailed as BOQ items. This allows authority engineers to instruct contractors to provide appropriate support based on ground conditions. Improving Health and Safety (HAC) systems, updating HAC manuals, and ensuring effective communication arrangements are also essential.
Precast elements that can be later converted into ducts or other facilities should be considered. These elements can be laid during tunnelling to streamline construction. Implementing mandatory 3D deformation monitoring can help detect problems early. A tunnel typically shows signs of deformation before collapsing, so catching these issues during the elastic phase is crucial.
We must acknowledge the government's efforts in handling the Silkyara tunnel accident. The leadership's approach - emphasizing safety, taking time, and mobilizing resources effectively - was commendable. The coordinated national effort and mature leadership from the Ministry of Road Transport ensured a well-managed response to the crisis.