Analysis of hydraulic breakdown and seepage of tail sealing system in shield tunnel machines

Abstract

The use of shield method in tunnel construction is limited by the engineering conditions of highwater pressure. This is mainly due to the uncertainty of the pressure-bearing capacity of the sealing chambers of the shield tail under different grades and conditions when subjected to different external water pressures. Therefore, it is crucial to determine the pressure-bearing capacity of the sealing chambers. However, there is a lack of studies on the calculating method of the pressure-bearing capacity, which requires more theoretical investigation. To explore the common patterns of multi-grade sealing-related parameters and quantify the pressure-bearing capacity of the sealing chambers, a breakdown and leakage model of the shield tail is proposed, targeting the basic sealing unit of the system. Based on non-Newtonian fluid dynamics and fractal theory of porous media, the model is used to calculate the breakdown pressure and grease seepage rate corresponding to tunneling and shutdown states. In addition, a hydraulic breakdown device of the sealing unit of the static shield tail is built to investigate the relationship between the shield tail clearance and the shield tail brush porous media area, which helps to verify the theoretical model. Finally, the analysis of sealing chamber geometry parameters, grease rheological parameters, and an environmental parameter using the proposed theoretical model shows that the pressure-bearing capacity of the shield tail can be improved by increasing the shield tail clearance and grease yield stress. It also shows that the length of the sealing chamber and the plastic viscosity of the grease do not have a significant effect on the breakdown pressure of the shield tail. The model proposed in this paper will provide ideas for the calculation of the pressure-bearing capacity of multi-grade sealing chambers in the future.

Keywords

Shield tunnel / High water pressure / Shield tail seal / Seal failure / Breakdown pressure / Seepage rate

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

CRediT authorship contribution statement

Dalong Jin: Writing - review & editing, Validation, Methodology, Investigation, Conceptualization. Zhuoyu Li: Writing - review & editing, Writing - original draft, Validation, Methodology, Investigation. Dajun Yuan: Writing - review & editing, Validation. Yangyang Gan: Validation. Jian Chen: Validation. Haipeng Guo: Validation.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The research work described herein was supported by the National Natural Science Foundation of China (Grant No. 52378387); the Beijing Nova Program (Grant No. 20220484037); China Railway 14th Bureau Group Corporation Limited Science and Technology R&D Program Subjects (No. 913700001630559891202201). These financial supports are gratefully acknowledged.

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