It is not correct to say that the entire operation will take over 24 hours as it totally depends on the spread of the debris and obstacles in terms of iron garters and machines which got buried under the rubble at the time of the roof collapse.
Over 100 hours after 40 workers were trapped inside the under-construction Silkyara tunnel in Uttarkashi following its roof collapse, the new "high-performance" American auger drilling machine, which was airlifted by IAF aircraft a day ago, started drilling on Thursday through the pile-up of debris accumulated inside the tunnel.
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The machine has penetrated af ew metres into the debris. Penetration speed can vary depending on the condition of debris since there are iron garters and machines buried underneath.