Cross-passages are reinforced concrete structures built in between either two tunnels (as in case of twin tunnel systems) or a tunnel and the ground surface. They are provided to serve two primary purposes namely, emergency escape and maintenance work.
|Spay shotcrete lining||Excavation|
|Installation of Lintel beam||Completed Structure of cross passages|
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|Installation in-progress||Installation of Ring beam|
Ring Beams are temporary propping of the main tunnel lining to support the hoop load in the lining and maintain the shape of the main tunnel lining. Ring beams are installed before break through for Cross Passage Construction
|Caisson/Shaft Sinking #1||Caission/Shaft Sinking #2|
Caisson/ Shaft sinking are watertight retaining structure. It is a cost effective alternative to construct shafts and are designed as the final reinforced concrete lining of the shaft to carry all earth and hydrostatic loads. A shaft is an underground vertical or inclined passageway.
Soil nailing is typically used to stabilize existing slopes or excavations. Soil nails are typically solid bars or fiberglass bolts that are installed into a pre-drilled hole that penetrates through the initial loose soil layers into the stable ground beneath and cement grouted into place.
Rock bolt is a long anchor bolt for stabilizing rock excavations, which may be used in tunnels or rock cuts. It transfers load from the unstable exterior to the confined (and much stronger) interior of the rock mass.