Rock Fragmentation and Cutting Mechanisms in Tunneling Systems

Tunnelling operations in civil engineering and mining rely extensively on the controlled fragmentation of rock to advance underground openings safely and efficiently. Central to most full‐face excavation systems is the tunnel boring machine (TBM), whose disc cutters impose concentrated contact stresses that induce tensile and shear fractures ahead of the cutter face. As the cutter penetrates, progressive microcracking coalesces into macroscopic chips or spalls, with the pattern and size of fragments governed by rock heterogeneity, confining pressure, cutter geometry and spacing, penetration depth and advance rate. Emerging hybrid cutting schemes, notably the integration of high‐pressure water jets, pre‐create kerfs to reduce cutter normal forces and specific energy, thereby prolonging tool life and raising advance rates. Numerical and experimental studies reveal that optimised cutter spacing mitigates interference between successive indentations and that coupled fluid–mechanical methods can decrease required energy by up to 40 per cent. Acoustic emission monitoring further elucidates crack initiation and propagation under varying water content, while discrete/finite element and smoothed particle hydrodynamics models offer predictive power over contact stresses, fragment size distribution and tool–rock interaction forces. Together, these advances underpin safer, faster and more predictable tunnel construction in diverse geological settings worldwide.

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Rock Fragmentation and Cutting Mechanisms in Tunneling Systems publication trend

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Technical terms

Tunnel boring machine (TBM): A mechanised excavation system that advances by rotating a cutterhead equipped with multiple disc cutters to fracture and remove rock.

Disc cutter: A circular, hardened steel tool mounted on the TBM cutterhead that applies concentrated loads to induce tensile and shear failure in rock.

Specific energy: The energy consumed per unit volume of excavated rock, used to evaluate cutting efficiency.

Acoustic emission (AE): Elastic waves generated by rapid release of strain energy during microcracking events, monitored to assess fracture progression.

Finite element method (FEM): A numerical technique that discretises a continuum into elements to solve stress, strain and deformation under applied loads.

Smoothed particle hydrodynamics (SPH): A mesh‐free computational method modelling fluids and solids by tracking particles, useful for simulating water‐jet‐assisted cutting.

References

1. Discrete/Finite Element Modelling of Rock Cutting with a TBM Disc Cutter. Rock Mechanics and Rock Engineering (2016).
2. A Closer Look at the Design of Cutterheads for Hard Rock Tunnel-Boring Machines. Engineering (2017).
3. Rock Breaking Performance of TBM Disc Cutter Assisted by High-Pressure Water Jet. Applied Sciences (2020).
4. Acoustic Emission Characteristics During Rock Fragmentation Processes Induced by Disc Cutter under Different Water Content Conditions. Applied Sciences (2019).