Abstract

Underground construction involves all sort of challenges in analysis, design, project and execution phases. The dimension of tunnels and their structural requirements are growing, and so safety and security demands do. New engineering tools are needed to perform a safer planning and design. This work presents the advances in the particle finite element method (PFEM) for the modelling and the analysis of tunneling processes including the wear of the cutting tools. The PFEM has its foundation on the Lagrangian description of the motion of a continuum built from a set of particles with known physical properties. The method uses a remeshing process combined with the alpha-shape technique to detect the contacting surfaces and a finite element method for the mechanical computations. A contact procedure has been developed for the PFEM which is combined with a constitutive model for predicting the excavation front and the wear of cutting tools. The material parameters govern the coupling of frictional contact and wear between the interacting domains at the excavation front. The PFEM allows predicting several parameters which are relevant for estimating the performance of a tunnelling boring machine such as wear in the cutting tools, the pressure distribution on the face of the boring machine and the vibrations produced in the machinery and the adjacent soil/rock. The final aim is to help in the design of the excavating tools and in the planning of the tunnelling operations. The applications presented show that the PFEM is a promising technique for the analysis of tunnelling problems.

Abstract

Abstract

Abstract

Tunnel collapse is a critical issue in geotechnical engineering, affecting the safety, functionality, and economic viability of underground structures. This study examines the primary failure mechanisms of tunnels, including roof instability, shear failure of sidewalls, base heave, wedge failure, and progressive collapse, with a particular focus on hydropower tunnels. The role of principal stress directions and stress redistribution in failure processes is analyzed, highlighting the effects of excavation-induced unloading, in situ stress concentration, and external influences such as groundwater infiltration and seismic activity. Special attention is given to hydropower tunnels, where transient hydrostatic pressure variations, mineralogical degradation, and high in situ stresses increase the likelihood of collapse. The study integrates limit analysis and fracture mechanics to model tunnel failure mechanisms, emphasizing how plastic deformation and crack propagation contribute to instability. Numerical simulations and real-world case studies illustrate the interaction between stress conditions and structural response. The findings suggest that tunnel stability is rarely governed by a single factor but rather by a combination of geological, structural, and environmental influences that evolve over time. Future research should focus on the development of real-time monitoring systems using artificial