Rock Mechanics
Dariush Mohammadi; Kourosh Shahriar; Parviz Moarefvand; Ebrahim Farrokh
Abstract
The correct design of the cutterhead of a tunnel boring machine (TBM) plays a vital role in the efficient operation of the machine, as the cutterhead structure remains unchanged during the tunneling project. This paper aims to elucidate the fundamental principles in the design of the cutterhead opening ...
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The correct design of the cutterhead of a tunnel boring machine (TBM) plays a vital role in the efficient operation of the machine, as the cutterhead structure remains unchanged during the tunneling project. This paper aims to elucidate the fundamental principles in the design of the cutterhead opening in soft ground based on data obtained from TBM manufacturers. Initially, a comprehensive database of soft ground cutterheads from different TBM manufacturers across various projects and ground conditions was compiled. The most frequently used cutterhead configurations with diameters exceeding 5 meters were categorized into 36 distinct opening configurations based on a radial opening ratio curve and opening patterns per sector. Next, the performance parameters and particle flow characteristics of three Herrenknecht cutterhead designs featuring varying opening configurations in the central and circumference areas were analyzed using the Discrete Element Method (DEM) by considering material parameters for machine and soil and contact parameters between soil particles and soil particles-machine structures. Hertz–Mindlin model was assigned as the contact model for these elements. Additionally, three different cutterheads employed in Tehran metro projects in Iran were identified by monitoring the cutterhead torque and thrust force under same geotechnical conditions and operational parameters. Generally, a higher opening percentage in the central area of the cutterhead indicates good performance during excavation in cohesive soils. However, the higher opening percentage in circumferential areas is a better choice for effective excavated material removal around the cutterhead and tunnel in non-cohesive soils, weathered rocks, mixed and heterogeneous conditions.
D. Mohammadi; K. Shahriar; D. Parsapour
Abstract
Tunneling in urban areas has always encountered many uncertainties, which if not considered in both analysis and design of the tunnels, will cause unexpected events during tunnel construction. Obstacles are among the most remarkable uncertainties in tunneling that affect the tunnel construction process. ...
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Tunneling in urban areas has always encountered many uncertainties, which if not considered in both analysis and design of the tunnels, will cause unexpected events during tunnel construction. Obstacles are among the most remarkable uncertainties in tunneling that affect the tunnel construction process. The obstacles in urban tunneling include municipal utilities, surface and sub-surface structures, channels, wells, storages, and unknown cavities. Tehran Metro Line 7 in Iran is no exception to the rule, and has been grappling with the obstacles. In this work, we investigate the effect of the existence of wells and unknown cavities in the zone of influence of excavated tunnels by EPBM. The innovation of this research work is in the EPB tunnel design encountering wells and cavities that are as risky as the adjacent underground structure. In this work, we use a numerical simulation of the 3D finite difference method (FDM) so a series of parametric studies based on the numerical model are examined using the well and unknown cavity geometry and their location relative to the tunnel in alluvium. According to the results obtained, a major disturbance occurs in the near field of the well–tunnel, and the interaction problem happens in front of the tunnel face. The numerical outcome indicates that the most critical state of the ground settlement by EPBM happens when the well and unknown cavity are located in the face of the tunnel. It is also proved that the ground behavior is different for each part of EPBM such as ahead of the face, cutter head, shield, and segmental lining parts.
