MARKET Underpass & Tunnel
Chiang Mai Middle Ring Road
NCE undertook the detailed design of seven underpasses and one major interchange on the Middle Ring Road in Chiang Mai.
The underpasses are designed as watertight structures to be permanently located under the ground water level. The prestressed bridge deck is supported by permanent sheet piles.
Excavation for the underpass shall be carried out in the dry underneath the bridge deck. Uplift of the tunnel section is controlled by the weight of the bridge deck in combination with vertical soil anchors.
Excavation for the approach troughs are carried out between temporary sheet piling supported by inclined soil anchors. Uplift of the open approaches is prevented by vertical anchors together with backfill behind the retaining walls.
The overpass is designed as a post-tensioned box girder bridge. Typical span length is 38 m, total length 370 m.