Special projects such as mining, tunneling, undersea tunnels, or those undertaking projects around hostile borders deserve special attention. These large and complex projects that are executed under extraordinary environmental conditions at times also require the customisation of equipment.
Prabhukumar LT, Assistant General Manager of L&T ECC, who has been associated with L&T for the past 14 years and the project head for Rs 2,000 crore Rishikesh Karanprayag railway tunnel package 2, spoke on the challenging situations and how innovation is helping in bringing about optimal solutions during the CONSTRUCTION TECHNOLOGY SUMMIT, held virtually on July 22-23, 2021.
Major tunnelling method used by L&T is the drill and blast method. “The goal of modern tunnelling technologies is to convert the unpredictable to predictable,” said Prabhukumar LT.
On the challenges faced in tunnelling, he said “Many projects are coming up near the Himalayan mountains. The Himalayan range are young mountains with highly varying geology, coupled with diversified problems such as difficult terrain conditions, thrust zones, shear zones, folded rock sequence, in-situ stresses, rock cover, ingress of water, geothermal gradient, etc., which makes them highly unpredictable. Major challenges faced by us are the geology and predicting things ahead. Due to unpredictable geology, safety is compromised during project work, which leads to extended project completion and cost over run.”
Said Prabhukumar LT, “During survey, the major challenge we face is during the pictorial output of profile geometry in real time at tunnel face. It was difficult to spot undercut/over break, and spot analysis of over break quantity. We also face problems like real time shotcrete layer thickness measurement and analyse the data to control overspray or underspray of shotcrete.
He added, “We implemented robotic survey profilers with Amberg and Trimble tunnel software. Using this, the real time analysis—excavation profile (undercut, overbreak) and shotcrete profile (underspray/overspray)—were easily available at site. Even 3D project can be prepared for the entire tunnel line, and it provides high accuracy and reduces cycle time.”
With automated drill jumbos, the data can be transferred from the office itself as it is WiFi-enabled. It gives efficiency of the drill, machine parameters, pull out analysis, round report analysis and drill tool life analysis.
“We are planning to implement thermal scanners, where it scans the surface and tells you immediately where the shotcrete is oversrpead or underspread. It gives real time data to the operator, and proper thickness and finishing,” he added.
The probe hole drilling and TSP system helps in prediction of face ahead and preplanning the works, detection of hazardous fault zones and cavities, exploration of water bearing formations and detecting changes in rock mechanical properties. The probe hole drilling machine can indicate rock fracture indicator, rock strength, drill parameters, round reports, and additional reports like water ingress and rock quality.
He added, “We also have rear view cameras on dumpers, telehandlers, and CCTV at all locations for better safety during continuous reverse operation inside the tunnel, and continuous monitoring.” The tunnel communication system and IOT provides remote data transfer between drill jumbos and the main office, and provides Internet connectivity inside the tunnel for communication. The IOT installed in vehicles is used to monitor real time fuel consumption. Even drones surveys are used for open works. It saves a lot of time and is effective.
He adds, “With this, we are going to give a safe working environment. We can take precautions before taking on something challenging since it gives a better idea of geological challenges ahead. There are a lot of savings on the cycle time. It gives 5 to 25% savings. The life of the project increases and it reduces 5-8% cost.”
Prabhukumar LT concludes, “Predicting the unpredictable is the essence of extreme project management in underground works.”