Centrifugal model test on the clay arching

This paper takes a sewage tunnel as an example, which crosses the Huangpu River in Shanghai. The pipe of the tunnel is made of prefabricated reinforced concrete and the outside diameter is phi 2500mm. The centrifugal model tests simulate the slump caused by the unbraced excavation of single clay hole and double holes. The effect of arching is analyzed through displacement field. The deformation during the braced excavation of double holes is analyzed and the superimposed soil pressure over the braced structure is measured. The experiment results show: during the excavation of single unbraced hole, the earth arch will emerge automatically. The arch is 5.1m high. While the excavation of the double unbraced holes, the thickness of superimposed soil is at least 7.0m. When the tunnel is braced, the arch will not emerge.