Abstract: The two-stage construction technology of pre-embedded sleeves and externally mounted channels adopted in shield tunnel sections of urban rail transit impose stricter construction constraints than traditional processes. Excessive construction deviations are prone to quality issues such as poor channel fitting and misaligned installation of electromechanical equipment. To determine the reasonable construction error control criteria of this technology, address the challenges in high-precision construction management, and ensure the installation quality of subsequent supports and equipment, this paper takes Guangzhou Metro Line 12 as the engineering background to carry out a systematic study on the construction accuracy of embedded channels in shield sections. Combined with the tunnel structural parameters, sleeve layout characteristics, and equipment installation conditions, the core design control factors of channel construction are sorted out. The limit probability method is adopted to calculate the fitting performance between T-bolts and channels, the installation adaptability of supports for various disciplines under different working conditions is analyzed, the allowable range of construction errors is defined, and targeted construction optimization measures are proposed. The main conclusions are drawn as follows: (1) The pre-embedded sleeve with externally mounted channel technology requires far higher construction precision than traditional processes, with narrower allowable construction error thresholds and stricter civil construction control standards. (2) The axis elevation error of shield tunnel alignment shall be strictly controlled within ±50 mm, which can effectively avoid channel installation defects and bolt matching failures. (3) The segment rotation deviation shall be controlled within ±1° to ensure the overall alignment smoothness of the channels and meet the standardized installation requirements of subsequent electromechanical equipment.

Key words: urban rail transit, embedded anchor channels, allowable construction tolerances, shield tunnel sections