Subway station construction parallelly below existing double-cell tunnel without clearance

Abstract

ABSTRACT A case of the Olympic Park Station of Beijing Subway Line 15 constructed parallelly below the Datun Road Tunnel without clearance using the pile-beam-arch (PBA) method was presented. Cross section, geological condition, and construction process of the subway station are illustrated. The strip foundation PBA approach was first adopted and the settlements of the existing tunnel due to new subway station construction are systematically monitored. Whereas this method could not satisfy the settlement requirements of the existing Datun Road Tunnel. The maximum settlement of the existing tunnel reaches 32.0 mm. Meanwhile, the maximum transverse differential settlement of the existing tunnel reaches 10.1 mm. The improved pile foundation PBA approach was proposed. The numerical simulation was performed to verify the feasibility. The results indicate that the pile foundation PBA approach is more efficient in existing tunnel settlement control than the strip foundation PBA approach. About 80% of the total settlement of the existing tunnel caused by subway station construction using the pile foundation PBA method is produced during the excavation of the drifts and the arches. The settlements of the original tunnel induced by the construction of the concourse and the platform account for about 20% of the total settlement. The increments are negligible after the completion of the concourse construction.