Steady Growth: Experience, challenges and best practices in tunnel construction

Experience, challenges and best practices in tunnel construction

Tunnelling activity in India has accelerated in recent years due to several growth factors. Increasing government support, adoption of cutting-edge technologies and processes, increased investments, and initiatives to improve rural connectivity are a few of them. In a panel dis­cussion at “Infrabuild India”, government and industry stakeholders discussed the experience so far in tunnel construction, tunnelling tech­niques, implementation of key tunnel projects, impact of Covid-19, issues and challenges faced, and upcoming opportunities. Excerpts…

Sanjay Dave Vice-President and Sector Head, Engineering Management (CEMG) & IMS, HCC India

  Sanjay Dave

HCC India has developed 364 km of tunnels, including 204 km in the rugged Himalayan re­gion. In a major development, the company has successfully completed the Kishanganga hy­dro­electric project with 14 km of tunnel boring machine (TBM) tunnelling and a record 816 metres in a month, after facing all the challen­ges and moving past all the difficulties.

HCC has a mix of engineering, procurement and construction contracts as well as item-rate contracts. The type of contract de­pends on time availability and the detailed project report (DPR) of the project. Given the un­predic­tability of environmental and geotechnical cir­cum­stances in the Hima­layas, geological surprise is one the biggest challenges faced in tu­n­nel construction in the region. There are ch­a­llenges in TBM operations in the Tapovan Vi­sh­nu­gad and Vishnugad Pipa­l­koti project.

Tunnel construction for metros is a complex job because of the congested environment. A complete DPR is created by the client/owner, including a geological base line report. However, there may be differences between the report and reality, resulting in changes in rock class and support systems, and extended time, clai­ms, arbitration etc.

Covid-19 had a significant influence on the sector, since guidelines were constantly changing. After the lockdown was lifted, the government provided no facility for workers to return to the construction site the way they enabled workers to reach their homes. Further, maintaining social distance while working was a tremendous challenge. Apart from this, wearing a personal protective equipment kit on sites lowers the productivity of workers.

The outbreak of the ongoing pandemic has brought attention to the potential and benefits of digital interventions. These include hands-free sanitisation for workers, use of various te­chnologies such as facial recognition and iris technology for attendance marking in place of touch-based biometric systems and use of drones to monitor the project’s progress at various sites. In assessing a work at project sites, artificial intelligence and PTZ cameras play a critical role. Data transfer and analysis have also been simplified. Geological conditions up to 100 metres are being assessed using tunnel seismic prediction (TSP) methods. Two- and three-dimensional de­sign tools are being used. Further, three-dimensional project simulation models are being used to train project engineers and labourers without compromising the safety of workers. Digitali­sation has resulted in an indirect increase in efficiency. Diesel-powered machinery makes it more difficult for workers to brea­the, which has made ventilation es­sential. Va­rious technological advancements have been im­plemented, including the use of gas detectors for tunnel development and the use of va­cuum and forced ventilation for all significant projects.

Future outlook

Tunnels are being actively constructed in difficult terrain to ensure that a strong ecosystem is established for swift implementation of tunnelling activities in the country. The tunnelling in­dustry has witnessed a steady increase in de­ma­nd from the infrastructure sector over the past few years owing to the growing needs of diverse sectors such as railways, metro syste­ms, roads, hydro­power, water supply and se­werage. Going forward, roads and railways in the North and North­east have a huge number of tunnelling oppo­rtunities coming up. There are also opportunities in the hydropower segment.

M.M. Madan Chairman, Tunnelling Group, ASSOCHAM’s National Council on Construction Equipment

M.M. Madan

By 2030, India has announced a target to ac­hieve 75 GW of installed capacity of hydroelectric power projects, which will be accomplished by 26,000 MW of new hydroelectric projects. Currently, over 9,000 MW of hydropower projects are under construction in Jammu & Ka­sh­mir, Himachal Pra­­desh, Uttarakhand, Aruna­chal Pradesh, Sik­kim, West Bengal and Andhra Pra­desh. Many prestigious hydropower projects had been taken over by private developers, but the progress of these projects was slow. Rece­n­tly, the prime minister announced the re-allotment of hydro projects that had previously been alloted to the private sector in Arunachal Pra­desh to PSUs such as NHPC, SJVN, NEEPCO, THDC, as well as the allotment of new projects to various states like Uttarakhand and Himachal Pradesh. Due to the availability of superior construction equipment and materials, modern technology, and application of better planning and execution strategies, tunnelling activity in India has impro­ved significantly in recent years. Previously, the Indian government did not focus much on hy­dropower development. However, it has been recognised that the country will be unable to progress without hydropower.

Currently, due to a sudden increase in execution of infrastructure projects in roads and highways, railways, metro, water supply and hy­dro­power projects,  there is a shortage of tra­in­ed wor­­kers and experienced construction engi­ne­e­rs, design engineers and contractors, among other issues. New contractors from infrastructure sector are shifting to the hydro sector, but they lack expertise and training. Through agreements with JVs, they will gain hydro expertise. As the hydro projects are located in unapproachable, high mountains, 100 per cent investigation of the geological technical parameters for project construction cannot be done, therefore preparing as accurate a GBR and risk sharing matrix as possible is the most important part of any contract. The risk sharing shall be pre-decided and a part of the contract. The sad part is that developers are keeping a ceiling on risk sharing, which tr­ou­bles contractors because it defeats the whole purpose for which it has been introduced in modern contract practices. This results in suffering for both contractors and owners and delays project execution. Due to Covid-induced restrictions on conducting workshops physically, engineers are being trained at a minimal cost via web workshops and webinars to understand how to plan and analyse the complexities of design. This will help enhance the design capacity of engineers.

The safety of workers on tunnelling projects is one of the areas that require utmost attention. To this end, safety equipment has been made man­datory and penalty fees are imposed in case of any violation, whether by engineers or co­ntractors. After the construction of tun­nels, a digital monitoring system should be ins­talled to monitor safety throughout the life of the tunnel. In case of any deformation after the construction of the tunnel, an alarm will go off, which will im­mediately give an alert to the owner of the pro­ject at their office or HQ. Going forward, the hydropower, roadways, railways and metro sectors will offer maximum opportunities in the tunnelling segment because of fast-track in­fra­s­t­ructure development being carried out in India.

Colonel Parikshit Mehra Commander 42, Border Roads Task Force, Border Roads Organisation

Colonel Parikshit Mehra

At a height of 10,000 feet, the Atal Tunnel is the world’s longest roadway tunnel. It has ins­tilled trust in tunnelling in any type of geology in the country. In the Ladakh region, several tunnelling projects have been planned. For river line projects, DPRs are being created. Initially, there was aversion towards the deployment of TBMs. However now, technological advancements in TBMs have made them more adaptable to varied geology.

Construction activities on tunnels at high altitudes face challenges pertaining to excavation and ventilation. The most challenging task is to keep working on the excavation during the wi­n­ter season when there is a lot of snow. Oth­er challenges faced during project execution include assembling workers in such poor wea­ther conditions and improper risk allocation. The risk should be divided between the owners and the contractors, forming a proper risk sharing matrix to safeguard the profits and interests of all stakeholders.

The Covid situation demands special measures. Teams should work in Bio Bubbles so that spread can be localised and minimised. Health and safety measures especially proper ventilation are the need of the hour to attract better manpower and reduce time required on excavation. This will aid in reducing project times and improving their economy. The crux of the FIDIC Emerald books is likely to find its way in Indian contracts within the next couple years.