Abstract:

A mined tunnel of Line 14 of Beijing Metro runs underneath the group piles of a large scale bridge. The group piles of the bridge are located in sandy cobble ground and there is strict requirement on the settlement of the bridge. Therefore, there are great risks in the construction of the mined tunnel. Most of the group piles are consolidated by composite bolt piles, while 2 group piles are not consolidated by composite bolt piles. Analysis is made on these two cases and conclusion is drawn that in sandy cobble ground, although the composite bolt piles can protect the bridge piles, the installation of the composite bolt piles can induce settlement to the bridge. It is proposed that whether composite bolt piles should be installed or not shall be determined according to the conditions of the sandy cobble ground so as to avoid unnecessary waste.

Key words: mined tunnel, sandy cobble ground, composite bolt pile, existing bridge pile, settlement