Modeling excavation chamber of EPB tunnel boring machine by discrete element method

Document Type : Research Article

Authors

University of Zanjan, University Blvd., Zanjan, I. R. Iran Email: international [at] znu.ac.ir, Tel: +98 (24) 33051, Postal Code: 45371-38791

Abstract

Earth Pressure Balance (EPB) tunnel boring machines are widely utilized for the excavation of subway tunnels. These machines leverage the pressure generated by the excavated materials within the excavation chamber to stabilize the tunnel face. The pressure in the excavation chamber is modulated by varying the speed of the screw conveyor, making the precise control of this rotation speed critically important. Such adjustments facilitate the management of the tunnel face and influence the overall settlement of the tunnel structure. This study models the tunnel excavation of Tabriz Metro Line 2, employing an EPB shield that operates under earth pressure conditions. The excavated material is accumulated in a chamber located behind the cutter-head, which generates the requisite pressure at the work face. This pressure is regulated through the screw conveyor mechanism. The simulation was conducted using a three-dimensional particle flow code based on the discrete element method. The findings indicate that when the pressure at the face is decreased to 50% of the maximum pressure exerted by the horizontal jacks of the shield drive, significant and hazardous ground surface settlements occur. Conversely, at elevated pressures, a consistent settlement of 1.9 cm was recorded. Additionally, a reduction in the cutter-head rotation speed from 2 rpm resulted in a decline of the work face, while an increase in speed corresponded with the same 1.9 cm settlement. The discrete element method effectively models the drilling process. The validity of the modeling outcomes was corroborated by data acquired from instrumentation.

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AUT Journal of Civil Engineering
Volume 9, Issue 1
In Progress
May 2025

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