Behavior of the ground in rectangularly crossed area due to tunnel excavation under the existing tunnel

摘要

In this paper, the study was focused on the ground behavior around tunnel-crossing zone and the existing tunnel behavior located above the newly excavated tunnel. Several large-scale model tests were carried out in the 1/12 scale for a field tunnel in practice where the upper tunnel had 7.2 m diameter and 8.4 m overburden and the lower tunnel of 10.8 m diameter was located below the upper tunnel with 8.4 m clearance. The 1/12 scale model was constructed in a large-scale test pit in the dimension of 4.0 m width, 3.8 m height and 4.1 m length. The ground density was controlled by sand raining to get uniform middle density. The existing upper tunnel had 60 cm diameter and the steel lining of 4 mm thickness. The upper tunnel lining was buried during the in situ ground build-up. The lower tunnel was excavated in 90 cm diameter and supported by steel liner of 4.5 mm thickness at each construction phase of 30 cm advance length.