The cutter head, a pivotal component of the tunnel boring machine (TBM), endures high-risk working conditions involving high temperature, pressure, and hardness. The intricacy and variability of working conditions give rise to high torque, substantial thrust, and stochastic impact loads, ultimately leading to the damage and failure of the cutter head. In this paper, the mechanical and fatigue properties of the 8 -meter-class spoke-web composite cutter head have been investigated through the finite element method (FEM) more academically. Specifically, this article explores the typical working conditions (full load, eccentric load, and extreme condition) and different geologies (soft soil, composite formation, and hard rock) that the cutter head encounters. The findings demonstrate that under extreme working conditions, the cutter head experiences a maximum equivalent stress of 250.76 MPa. Additionally, the maximum displacement of 4.83 mm occurs on the outer ring when subjected to a one-half eccentric load. Concisely, the FEA validates the cutter head's structural rationality in stiffness and strength. Furthermore, a fatigue durability analysis of the cutter head structure was conducted using nCode DesignLife based on the stress method, determining its fatigue life range to be between 6.857E+4 and 1.253E+7 cycles, with an error not exceeding 20% compared to the theoretical fatigue life. This research provides valuable insights for the structural design and fatigue life studies of cutter heads for TBMs.

This paper presents a method to predict the impact of underground tunnel construction on nearby piles using non-linear soil-pile-tunnel interaction. Two stage analysis method have been used considering Kerr foundation model. Greenfield ground settlements have been compared with site-specific instrumentation data of East-West Metro Project, Kolkata, India and results obtained were found to be in good agreement. It has also been observed that the Kerr foundation model considers soil spring over Pasternak's model and hence yields reduced pile deflection compared to Pasternak's model. Non-linear analysis considers non-linear stress-strain relationship and so yields more pile deflection than linear analysis under large deformation. Validation has been performed with case studies in published literature. Irrespective of end conditions, critical bending moment in pile develops at the tunnel centreline depth and at the fixed ends. Soil is a non-elastic material and due to its own shearing strength, the soil also absorbs some portion of the ground deformation before transferring that to the pile. So, consideration of non-linear Kerr model captures a realistic response of the pile. An accurate and cost-effective solution method of non-linear tunnel-soil-pile interaction model has been developed for easy application by practicing engineers using MATLAB software which is commonly available in most of the design.

The deep geological repository for radioactive waste in Switzerland will be embedded in an approximately 100 m thick layer of Opalinus Clay. The emplacement drifts for high-level waste (approximately 3.5 m diameter) are planned to be excavated with a shielded tunnel boring machine (TBM) and supported by a segmental lining. At the repository depth of 900 m in the designated siting region Nordlich Lagern, squeezing conditions may be encountered due to the rock strength and the high hydrostatic pressure (90 bar). This paper presents a detailed assessment of the shield jamming and lining overstressing hazards, considering a stiff lining (resistance principle) and a deformable lining (yielding principle), and proposes conceptual design solutions. The assessment is based on three-dimensional transient hydromechanical simulations, which additionally consider the effects of ground anisotropy and the desaturation that may occur under negative pore pressures generated during the drift excavation. By addressing these design issues, the paper takes the opportunity to analyse some more fundamental aspects related to the influences of anisotropy and desaturation on the development of rock convergences and pressures over time, and their markedly different effects on the two lining systems. The results demonstrate that, regardless of these effects, shield jamming can be avoided with a moderate TBM overcut, however overstressing of a stiff lining may be critical depending on whether the ground desaturates. This uncertainty is eliminated using a deformable system with reasonable dimensions of yielding elements, which can also accommodate thermal strains generated due to the high temperature of the disposal canisters. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

A major full-scale experiment called the Tunnelling and Limitation of Impacts on Piles (TULIP) project was conducted in 2020 on Line 16 of the Grand Paris Express project to analyze the tunnel boring machine-soil-pile interactions during tunnel excavation near deep structures. This paper presents the greenfield ground response observed when the tunnel boring machine (TBM) crossed the TULIP site: surface displacements, subsurface displacements, and pore water pressures are presented. The originality of the paper lies in the fact that details are provided not only on the site geological and geotechnical characteristics, but also on the TBM operation: a detailed analysis of the variations in pressure inside the cutting chamber of the earth-pressure balanced machine (EPBM) is proposed. This paper reports factual data without bias induced by a preconceived numerical model, but highlights open questions that challenge the advanced numerical models, that will be required to analyze completely the tunnel-soil-pile interactions.

Artificial fractures on the tunnel face can promote tunnel boring machine (TBM) performance in the intact rock mass with high rock strength. High-pressure water jet (HPWJ) is a feasible choice to pre-cut the kerfs on the tunnel face to assist in TBM tunnelling. To study the effects of different layouts of the TBM cutter and HPWJ on the cutting performance and the corresponding rock breakage mechanism, a series of full-scale linear rock cutting tests were conducted. The analysis included the TBM cutter force, cutter vibration, rock muck and rock-breaking specific energy. According to the results, two HPWJ-assisted cutting layouts are recommended. One is arranging the HPWJ nozzle ahead of the cutter, making the cutter cut along the kerf. The rock damage zone after the cutter penetration was rather limited since the kerf beneath the cutter prevented the formation of the pressurized crushed zone and the generation of the lateral cracks that occurred in the intact rock. The lowest cutter force and vibration were obtained with the shallow kerf depth compared with the other layouts. Creating kerfs with a depth slightly lower than the cutter penetration is suggested to vastly save energy. Another recommended layout is arranging the nozzles between all the cutter trajectories, making the cutter cut along the middle line of two kerfs. The breakage mechanism turned to the interaction between the cutter and adjacent kerfs, macro-cracks generated from the cutter tip could propagate to the bottom of kerfs on both sides. The cutter force and the magnitude of oscillations decreased with the increasing kerf depth. The largest rock-breaking volume and lowest specific energy were obtained among all the tests. The suggested kerf depth is about twice the cutter penetration, above which the specific energy would not significantly decrease. The study is helpful to the cutterhead design of the TBM assisted with HPWJ and the promotion of TBM performance. Linear cutting tests using the HPWJ and full scale TBM cutter were successively performed with various layouts.The analysis of cutter performance comprises force, induced vibration, specific energy and mucks characteristics, validating the feasibility of the assistance of HPWJ.Arranging HPWJ nozzles on and between the cutter trajectories were recommended to drastically reduce the cutter force and specific energy, respectively