Rock bolt failures in Tala Hydropower plant have decreased over the years. The last such failure the plant saw was in August. Rock bolt is an anchor bolt drilled inside the rock strata of the tunnel to stabilise it.
Records show that only about 3 percent of the total rock bolts installed have reportedly failed so far, a significant improvement from 2005. In 2005, Tala Hydropower plant, which was yet to be commissioned then, reported around 73 rock bolt failures.
Over 7,200 rock bolts were installed during the construction of the plant in 2003. Of it, about 229 rock-bolt failures have been reported till date.
“We have noticed the failure of rock bolts since construction period. Usually, some rock bolts just come out. During such incidents, it is very risky for the people working in the powerhouse. It is also very risky for the electro-mechanical equipment installed in the powerhouse,” said the Officiating Chief Engineer of Tala Hydropower plant, Kencho Gyeltshen.
He added that active seismic movement in the area could have been a reason for the huge number of rock bolt failures in 2005.
However, according to the report generated using online micro seismic system, the rock strata in the area is said to have stabilised over the years.
Through the system, sensors are drilled inside the rock as deep as 15-20 metres and any slight seismic activities are recorded in the acquisition system. “No abnormal activities are detected by the monitoring system. So far, whatever report we got out of the data analysis from the online micro seismic system has shown us that it’s stabilising.”
To reduce risks to workers and equipment from rock bolt failure, wire mesh protection has been fixed across some part of the powerhouse. Similarly, wire mesh has also been put in place to prevent damages of cables by the falling rock pieces.
