Abstract:

An urban metro tunnel crosses the pile foundation of an existing bridge abutment; and the pile foundation is close to the contour line of the metro tunnel (about 1.0 m); hence, great impact would be induced by shield construction. In order to reduce the risk of shield construction and ensure the smooth construction of the tunnel, the distance between pile foundations should be detected before construction to provide the basis for determining the construction scheme of shield tunneling. Due to the limitation of the ground traffic and construction space condition, geophysical methods can only be used for detection. The comparison results show that by using three kinds of crosshole CT methods can meet relevant requirements. Finally, the borehole verification is carried out according to the detection results; the results show that the geophysical exploration results are accurate and reliable.

Key words: metro shield tunnel section, spacing of pile foundation, geophysical detection method, crosshole CT method