Abstract: Ultradeep shaft construction in centrallylocated urban areas with large building density and small available space often faces a series of technical problems. Hence, a new shaftconstruction technology and automatic mechanical machine are introduced to address these problems. Based on the construction of a fullyprefabricated assembled shaft, the design and assembly of prefabricated shaft segments, undrained mechanical excavating technology, sinking control technology, shaft attitude control, and deviation correction technology are studied. The engineering practices show the following: (1) Prefabricated construction and undrained excavation can effectively control the instability risk of sidewalls and excavation faces, as well as the surface settlement. (2) Multiple attitude monitoring system with deviation judgment standards and correction measurements can ensure the shaft axis. (3) Adoption of overexcavation combined with the controlled sinking method can completely avoid sudden sinking and stagnation.

Key words: assembled shaft, shaft excavating machine, waterrich composite strata, undrained excavation, automatic mechanical method