Abstract: Three kinds of excavation blind area pretreatment methods are proposed to improve the applicability of the various cutterheads driven using central shaft, eccentric shaft swing, and planetary wheel of the existing noncircular tunnel boring machine(TBM) in composite strata. These methods include smalldiameter rock drilling combined with soil backfilling, hard rock pipe jacking combined with pipe joint soil backfilling, and blind hole host back combined with soil backfilling. These methods are developed based on the geological conditions of rock strength, range, and length in the noncircular tunnel and are successfully applied in the exit and entrance sections of a metro project. Moreover, a synchronous excavation system for multirotating cutterheadintegrated excavation blind area treatment devices is analyzed to achieve successful onetime excavation of noncircular TBM in composite strata. To further improve the excavation process, two kinds of excavation blind area treatment devices are designed and validated using the finite element method. These devices include the swing milling head and milling drum and are applied to a rectangular pipe jacking project in composite strata. Finally, excavation data is analyzed, and the driving parameters of the swing milling head and milling drum equipment are obtained. This new solution for the construction of noncircular tunnels in composite strata has the potential to greatly improve the efficiency and safety of tunnel excavation projects.

Key words: noncircular tunnel boring machine, composite strata, excavation blind area, swing milling head, milling drum