To make the initial cutting of the concrete plug, a manhole was created by drilling 24 overlapping boreholes through the 2.5 m thick concrete plug.
Some small diameter boreholes were drilled to allow a wire-saw to be used. This allowed large blocks of the concrete plug (2.5 x 0.45 x 0.88m) to be removed. These blocks could then be removed to allow entrance to GMT cavern.
![]() The initial cutting of concrete plug |
![]() Cutting of concrete plug |
![]() The first excavation of backfill |
![]() Removal of the plug sections after sawing |
![]() The cores of the concrete plug |
![]() Removal of the sawn concrete plug |