a heavy drilling machine was airlifted from delhi on wednesday to replace the “failed” equipment which was being used earlier to create a passage for 40 workers trapped in an under-construction tunnel that collapsed three days back, officials said. the new machine, that landed at the chinyalisaur helipad, over 30 kilometres from the tunnel on the chardham route, is being put into service, amid apprehension by workers at the site on the progress of the multi-agency rescue operations. workers chanted slogans