A Bored Tunnel on Kaohsiung Rapid Transit System, Contract CR2

Shield-machine bored tunnels are used for a variety of purposes in urban areas. Construction of these bored tunnels in soft ground can induce ground movement and cause damage to adjacent structures. Observation of soft ground tunnels in clay have been popularly discussed but there is limited literature on soft ground tunnels constructed in sand. A complete case record is given in this paper based on tunnels on Contract CR2 of the Kaohsiung Metro. It shows the accumulated maximum surface settlement induced by tunnelling can be up to 40 mm and that the ground becomes stable 20 to 40 days after the shield has passed. This paper explores the effects from two factors on the transverse surface settlement trough, ground loss rate (V) and settlement trough factor (K). Back-analyses indicate that approximately 0.31 to 1.85% of V and 0.4 to 0.9 of K were induced by the tunnelling works. In addition, three construction parameters, chamber pressure coefficient (Pr), backfill rate and backfill pressure were calculated and discussed. It is observed that Pr is mainly in the range of 0.7 to 0.9, backfill rate varies from 100 to 150% and the applied backfill pressure varies from 200 to 500 kPa during the construction. Due to limited data, no firm relationship could be established between construction parameters and V therefore further investigation is required.

並列關鍵字

Tunnelling in sand ； settlement ； ground loss ； settlement trough factor

國際替代計量

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