Abstract
It is generally accepted that selecting the key segment position for trapezoidal tapered rings and controlling the shield machine advancement are challenging tasks for shield tunneling projects. In this work, we propose a method for calculating the key segment position based on the shield tail gap, jack stroke difference, and lining trend. To calculate all possible key segment positions other than that corresponding to the straight joint configuration, the shield tail gap that remains after segment assembly and the jack stroke difference corresponding to the advancement of the segmental lining and lining trend were computed; then, values and importance coefficients were assigned to these factors according to current operating conditions. To ensure that the segmental lining can be assembled successfully with the calculated key position, we established a model to calculate the change in the shield tail gap before and after shield machine advancement based on the spatial relationships of the shield machine, the currently installed segmental rings, and the segment to be installed. Further, we propose a method for calculating the range of jack stroke differences when the predetermined “permitted shield tail gap” and key position are provided. The method is based on the change in the shield tail gap calculated with the above model and the positional relationship between the shield machine’s actual axis and the designed tunnel axis after the current segmental ring has been assembled. The calculated range of jack stroke differences may then be used to control the advancement of the shield machine. We validated the viability of our methods by using the data of Phase 1 works on Line 2 of the Ningbo Rail Transit system.
Highlights
In the field of urban tunnel construction, shield tunneling has become the preferred method, as it causes minimal ground disturbance and allows for fast construction. e trapezoidal tapered ring is a tunnel lining method that is becoming increasingly popular because of its cost-effectiveness, simple construction, and adaptability for a wide range of radius curves [1]
Based on a review of previous relevant studies, we propose a method for key position selection based on the shield tail gap, jack stroke difference, and lining trend
We constructed a method for calculating the range of jack stroke differences with predetermined key positions and a userdefined permitted shield tail gap to ensure that a segmental ring can be safely installed in the calculated key position
Summary
In the field of urban tunnel construction, shield tunneling has become the preferred method, as it causes minimal ground disturbance and allows for fast construction. e trapezoidal tapered ring is a tunnel lining method that is becoming increasingly popular because of its cost-effectiveness, simple construction, and adaptability for a wide range of radius curves [1]. If the advancement of the shield machine is not controlled as per operating conditions, it may become impossible to install the segmental ring with its calculated key position, which will subsequently affect the quality of the construction. Even after the key position of the segment to be installed has been determined, a mature and reliable method for controlling shield machine advancement toward the segmental ring does not currently exist. We constructed a model for calculating the change in shield gap before and after shield machine advancement, and we propose a method for calculating the key position based on the shield tail gap, jack stroke difference, and lining trend. We established a method for calculating the range of jack stroke differences for shield machine advancement to the ring when the key positions are fully determined and a “permitted shield tail gap” has been defined. We established a method for calculating the range of jack stroke differences for shield machine advancement to the ring when the key positions are fully determined and a “permitted shield tail gap” has been defined. is method is based on the positional relationship of the shield machine’s actual axis with the designed tunnel axis after the current ring has been assembled
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