Abstract: According to the notice issued by the General Office of the State Council on enhancing drinking water safety guarantees, large mountainous cities in southwestern China need to construct numerous water conveyance tunnels to achieve interconnection between backup reservoirs-water supply clusters and water supply clusters. Due to its superior technological and environmental advantages, pipe jacking has been widely used in the construction of these tunnels. In response to the lack of a calculation method for frictional resistance when pipe jacking traverses fault zones with fractured rock, this research relies on the Guanjingkou water control project in Chongqing, one of the 172 major water conservancy projects for water-saving and water supply determined by the State Council. Through on-site monitoring of jacking forces and investigation of sediment accumulation around the pipe sections in deep and extensive fault zones with fractured rock, the extent of sediment filling in the over-excavated gap before and after reinforcement of the fault zones is revealed. Two mechanical models for the contact between the pipe and the surrounding rock are proposed, and based on Janssen’s theory, the elastic-plastic theory of rock, and the multi-layer cylinder model, corresponding calculation methods for the frictional resistance of pipe jacking are derived for the two mechanical models. The applicability of these friction calculation methods for pipe jacking traversing fault zones with fractured rock is verified by comparing on-site friction monitoring data with theoretical calculation values.

Key words: pipe jacking, fault fracture zone, Janssen’s theory, frictional resistance, calculating method