Abstract: In order to grasp the comprehensive influence law of shield tunneling parameters and geological conditions on surface subsidence between shield intervals in sandy gravel stratum, a shield interval of Chengdu Metro is chosen as a case study, combined with the relationship between the surface subsidence and tunneling parameters of the our study team in the early stage, the total thrust，cutter head speed，screw machine speed，overlying soil thickness，groundwater level and gravel stratum thickness are determined as clustering indexes. The K-means algorithm is applied to cluster the actual monitoring data of each parameter index, and the influence of each index on the surface subsidence is analyzed comprehensively. The research results show that: 1) According to the results of K-means clustering, the monitoring points, corresponding to construction sections, are divided into three risk levels of surface subsidence, 1－3 is strong dangerous (Grade Ⅰ), 7－13, 16－19, 25－34 are weak dangerous (Grade Ⅱ), 4－6, 14－15, 20－24 are safe (Grade Ⅲ). 2) According to the clustering results, there is a positive and negative correlation between tunneling parameters, stratum structure and surface subsidence in a specific range. 3) Through an analysis of the relationship between geological structure, tunneling parameters and surface settlement, it is determined that when the overlying soil layer is thick, the groundwater level is low, and the gravel layer is thick, the control range of excavation parameters is a total thrust of 29 034.00-31 181.95 kN, cutterhead rotation speed of 1.25-1.32 r/min, and screw conveyor rotation speed of 6.13-6.98 r/min. When the overlying soil layer is thin, the groundwater level is low, and the gravel layer is thin, the control range of excavation parameters is a total thrust of 34 419.89-36 867.28 kN, cutterhead rotation speed of 1.44-1.45 r/min, and screw conveyor rotation speed of 5.74-6.99 r/min.

Key words: sandy gravel stratum, shield, surface subsidence, clustering analysis