Causes of reduction in shield TBM performance – A case study in Seoul

► TBM field measurement data in Han River riverbed were summarized. ► Thrust and penetration rate in the given section were specified. ► A number of disc cutter consumption and types of abrasion were analyzed. ► An exhaust ratio of screw conveyor and that of design problem were analyzed. ► The lack of penetration depth was mainly caused by lower thrust. This study investigates the fundamental reasons of reduction for excavation performance on shield TBM in the Han River riverbed tunnel by means of analysis of field measurement data. For the study: (1) measurement data were analyzed by both the thrust and penetration rate data in a given section with rock types and direction types, (2) a number of disk cutter consumption and types of abrasion were analyzed, (3) an exhaust ratio of screw conveyor and design problem of screw conveyor were analyzed by earth mud which becomes the rock powder. As a result of this study, it was found that the lack of penetration depth caused by lower thrust, disk changes according to rapidly changing rock types, and installed angle of screw conveyor, play an important role in the excavation performance.