Abstract:

The bored secant pile constructed by backcycling drilling machine under low clearance is discussed by taking the opencut foundation pits on double lines of Honggu Immersed Tunnel in Nanchang for example. The underground cable crossing the foundation pits is protected by concrete support; and the Ishaped steel and shotcrete support is constructed by topdown method. The ground around 110 kV cable is consolidated by highpressure jet grouting pile out of foundation pit; and the water curtain is constructed by vertical highpressure jet grouting pile under cable in foundation pit to stop the water and the emergency dewatering well at connecting point between retaining walls is constructed. Finally, the foundation pits have been successfully and safely constructed under complex conditions.

Key words: bored secant pile, highpressure jet grouting pile, cable suspension protection, Ishaped steel and shotcrete support, dewatering of foundation pit