Silt, seeping water: Here’s what is hampering the SLBC rescue op | Hyderabad News
Hyderabad: Despite deploying over 1,000 personnel from 11 elite agencies in the past seven days, the Telangana govt is struggling to complete the rescue of the eight workers buried under the collapsed roof of the Srisailam Left Bank Canal (SLBC) tunnel at Domalapenta village in Nagarkurnool district.
The roof collapsed at 13.90 km from the mouth of the tunnel at about 8.30 am Feb 22. At the time, 55 workers were on the first shift, including 40 from Jaiprakash Associates (Jaypee Group) and another 15 from Robbins company, engaged by the Jaiprakash to dig the tunnel.
Those involved in the rescue for the past seven days include the Indian Army, Indian Navy commandos, National Disaster Response Force (NDRF), State Disaster Response Force (SDRF), rat miners, Border Road Organisation (BOR), South Central Railway, and private firms such as L&T, Navayuga.
But they have struggled to complete the operation. Here’s why.
Silt a major challenge
A huge quantity of slush estimated to be about 10,000 cubic metres spread over 500 metres is posing a major problem. Its depth ranges from 7 feet to 10 feet near the collapsed site. The silt includes debris of the massive Tunnel Boring Machine (TBM) which is now badly damaged. The teams could not even reach the last point, the collapsed site, for two days due to the silt. Using machines and conveyor belts to remove the silt too is difficult as the passageway is narrow, and the belts have been damaged with overuse in the past couple of days. The rescuers started using nearly 300 workers to remove the silt manually and shift it out of the tunnel in the locomotive. The present focus is about 200 metres from the incident site, where the missing persons are believed to be trapped.
Huge seepage of water
Seepage of large quantities of water from the collapsed roof of the tunnel has hampered rescue operations. Rescue teams including rat miners and National Disaster Response Force (NDRF) noticed water oozing out at the rate of 3,600 litres to 5,000 litres per minute. This was mixing with the silt making it increasingly difficult to locate the missing workers. Since dewatering is a must to carry out rescue operations, the irrigation department brought two 100 hp pumps and a 500 KVA generator to continuously remove the water from the tunnel.
Conveyor belt damaged
There is a conveyor belt in the tunnel covering about 13 km of the 14-km tunnel. Since the tunnel locomotive cannot reach the crash site with water and silt, the rescue teams and officials reached the TBM location by using a conveyor belt for about 1.5 km from 12th km to 13.5th km. But with continuous movement, the belt got loosened and damaged in some places. The belt has not been functioning for the past three days.
Tunnel locomotive could not go up to TBM
The incident happened at 13.90 km but the rescuers could not go beyond 11.5 km in the tunnel locomotive due to silt and water and the damaged tracks. The teams repaired the track and brought it to about 12 km later. The locomotive is used to bring men and material from the mouth of the tunnel to the project site. Now it is being used to shift the slush that is lifted by the rescue teams.
Damaged TBM removal a big task
The 200-metre-long Tunnel Boring Machine (TBM), weighing about 1,500 tonnes, is the main machinery to drill the tunnel. Considering the size and weight of the TBM, the company Robbins, assembled the machine onsite and has been using it. At the time of the roof collapse, the eight workers were working in front of the TBM and could not escape the falling debris, while others working on other side of the TBM came out safely. Since the TBM is also damaged in the collapse, it is being cut up and dismantled using Ultra Thermo plasma cutters and other welding machines. This will make it easier to remove the silt with earthmovers.
The roof collapsed at 13.90 km from the mouth of the tunnel at about 8.30 am Feb 22. At the time, 55 workers were on the first shift, including 40 from Jaiprakash Associates (Jaypee Group) and another 15 from Robbins company, engaged by the Jaiprakash to dig the tunnel.
Those involved in the rescue for the past seven days include the Indian Army, Indian Navy commandos, National Disaster Response Force (NDRF), State Disaster Response Force (SDRF), rat miners, Border Road Organisation (BOR), South Central Railway, and private firms such as L&T, Navayuga.
But they have struggled to complete the operation. Here’s why.
Silt a major challenge
A huge quantity of slush estimated to be about 10,000 cubic metres spread over 500 metres is posing a major problem. Its depth ranges from 7 feet to 10 feet near the collapsed site. The silt includes debris of the massive Tunnel Boring Machine (TBM) which is now badly damaged. The teams could not even reach the last point, the collapsed site, for two days due to the silt. Using machines and conveyor belts to remove the silt too is difficult as the passageway is narrow, and the belts have been damaged with overuse in the past couple of days. The rescuers started using nearly 300 workers to remove the silt manually and shift it out of the tunnel in the locomotive. The present focus is about 200 metres from the incident site, where the missing persons are believed to be trapped.
Huge seepage of water
Seepage of large quantities of water from the collapsed roof of the tunnel has hampered rescue operations. Rescue teams including rat miners and National Disaster Response Force (NDRF) noticed water oozing out at the rate of 3,600 litres to 5,000 litres per minute. This was mixing with the silt making it increasingly difficult to locate the missing workers. Since dewatering is a must to carry out rescue operations, the irrigation department brought two 100 hp pumps and a 500 KVA generator to continuously remove the water from the tunnel.
Conveyor belt damaged
There is a conveyor belt in the tunnel covering about 13 km of the 14-km tunnel. Since the tunnel locomotive cannot reach the crash site with water and silt, the rescue teams and officials reached the TBM location by using a conveyor belt for about 1.5 km from 12th km to 13.5th km. But with continuous movement, the belt got loosened and damaged in some places. The belt has not been functioning for the past three days.
Tunnel locomotive could not go up to TBM
The incident happened at 13.90 km but the rescuers could not go beyond 11.5 km in the tunnel locomotive due to silt and water and the damaged tracks. The teams repaired the track and brought it to about 12 km later. The locomotive is used to bring men and material from the mouth of the tunnel to the project site. Now it is being used to shift the slush that is lifted by the rescue teams.
Damaged TBM removal a big task
The 200-metre-long Tunnel Boring Machine (TBM), weighing about 1,500 tonnes, is the main machinery to drill the tunnel. Considering the size and weight of the TBM, the company Robbins, assembled the machine onsite and has been using it. At the time of the roof collapse, the eight workers were working in front of the TBM and could not escape the falling debris, while others working on other side of the TBM came out safely. Since the TBM is also damaged in the collapse, it is being cut up and dismantled using Ultra Thermo plasma cutters and other welding machines. This will make it easier to remove the silt with earthmovers.
