Abstract: The settlement control is of great significance in largediameter shield launching underneath highpressure gas pipeline group in sandycobble strata. Hence, researches are conducted on reinforcement scheme, construction technology and parameters control of a largediameter shield launching underneath pipeline group at Wenquan Avnue stationMingguang station section on Chengdu metro line 17 using program demonstration and onsite measurement methods. The results show the following. (1) The surface settlement induced by the shield launching in sandycobble strata can be effectively controlled using combination scheme of doublelayer large pipe roof, Soletanche grouting and well point dewatering. (2) The settlement of pipeline in sandycobble strata can be effectively controlled by adopting the protection measures of strip foundation reinforcement and steel wire suspension fixation. (3) The recommended twostage control parameters for shield launching underneath pipeline in sandycobble strata are proposed based on the excavation test of shield tunnel in the same geological conditions and buried depth. (4) The pipeline settlement monitoring data show that the cumulative settlement of the pipeline during shield tunneling is within the control standard.

Key words: sandycobble stratum, shield tunnel, launching underneath pipeline group, tunneling parameters