Janosch Stascheit

Computational Simulation of Mechanized Tunneling as Part of an Integrated Decision Support Platform

Mechanized tunneling is characterized by a staged procedure of excavation and lining erection and continuous support of the soil by means of supporting fluids (or compressed air) at the tunnel face and pressurized grouting of the tail gap. The interactions between the tunnel boring machine (TBM), the support measures, and the soil, including the groundwater, determine the efficiency, safety, and effects on the existing infrastructure. In this paper, a process-oriented numerical simulation model for mechanized tunneling and its integration in the context of an integrated optimization platform for tunneling (IOPT) is addressed. The simulation model is based upon the finite-element method and considers the transient excavation process and all relevant components, support measures, and processes, along with their interactions during tunnel advance. In particular, the model allows the investigation of the effects of drilling and stand-still periods upon the generation of a filter cake at the tunnel face. This ...

Advanced finite element modeling of excavation and advancement processes in mechanized tunneling

A computational framework for modeling curved tunnel advancement is proposed.A steering-correction algorithm for the advancement of the TBM is developed.The continuous excavation process is modeled using adaptive remeshing.All relevant interactions between tunnel construction and the soil are considered. Mechanized tunneling is characterized by complex interactions between the shield machine and the surrounding ground during the TBM advancement process. In this paper, a new computational framework is developed to enable an efficient and realistic three-dimensional modeling of the tunneling process for arbitrary alignments using the finite element method. A new steering algorithm for the advancement of the Tunnel Boring Machine (TBM) for arbitrary alignments during shield tunneling is incorporated in the proposed model. This algorithm simulates the shield behavior and accordingly provides the numerical model with the required information to keep the TBM on track during the simulation. However, the utilization of this algorithm is only possible using a finite element discretization which adapts to the actual motion path of the shield machine. For this purpose, a re-meshing technique is proposed in order to automate the process of mesh generation in the vicinity of the tunnel face, denoted as the region of interest, within the advancing process. The combination of a computational steering algorithm and a 3D automatic adaptive mesh generation procedure form a novel framework for process oriented finite element simulations of the mechanized tunnel construction process. The applicability of the proposed modeling technique for predicting the shield behavior and the soil-tunnel interactions during tunneling along curved alignments is demonstrated by means of selected examples.

An integrated platform for design and numerical analysis of shield tunnelling processes on different levels of detail

Building and construction information modelling for decision making during the life cycle of infrastructure projects are vital tools for the analysis of complex, integrated, multi-disciplinary systems. The traditional design process is cumbersome and involves significant manual, time-consuming preparation and analysis as well as significant computational resources. To ensure a seamless workflow during the design and analysis and to minimise the computation time, we propose a novel concept of multi-level numerical simulations, enabling the modelling on different Levels of Detail (LoDs) for each physical component, process information, and analysis type. In this paper, we present SATBIM, an integrated platform for information modelling, structural analysis and visualisation of the mechanised tunnelling process for design support. Based on a multi-level integrated parametric Tunnel Information Model, numerical models for each component on different LoDs are developed, considering proper geometric as well as material representation, interfaces and the representation of the construction process. Our fully automatic modeller for arbitrary tunnel alignments provides a high degree of automation for the generation, the setup and the execution of the simulation model, connecting the multi-level information model with the open-source simulation software KRATOS. The software of SATBIM is organized in a modular way in order to offer high flexibility not only for further extensions, but also for adaptation to future improvements of the simulation software. The SATBIM platform enables practical, yet flexible and user-friendly generation of the tunnel structure for arbitrary alignments on different LoDs, supporting the design process and providing an insight into soil-structure interactions during construction.

Numerical Simulation of Interactions between the Shield-Supported Tunnel Construction Process and the Response of Soft Water-Saturated Soils

During the design and construction of shield-driven tunnels, a reliable analysis of the construction process is required for the prognosis of the process-induced surface settlements, changes in soil stresses, and changes in groundwater conditions, as well as for the determination of the loads acting on the tunnel tube and on the tunnel-boring machine. In this context, numerical simulation methods like the finite-element method allow for a realistic description of the construction process and its impact on the surrounding underground. The investigated problem is governed by the interactions between the tunneling process and the surrounding underground and its constituents—soil grains, groundwater, and pore air. The tunnel-construction process interacts with the surrounding underground via the heading face support, by frictional contact between shield skin and soil, and because of grouting of the annular gap. Considering these interactions, a holistic simulation model is presented for the process-oriented simulation of shield-supported tunnel advance and its interactions with fully saturated, partially saturated, or nonsaturated soft soil. Its applicability is demonstrated by selected simulations of real-scale examples. Parametric studies are performed to investigate the influence of soil conditions and of process parameters on the time-variant settlements and groundwater conditions, showing its capabilities with respect to the simulation of the soil-process interactions in front, above, and behind the tunnel-boring machine.

Adaptive Computational Simulation of TBM-Soil Interactions during Machine-Driven Tunnel Construction in Saturated Soft Soils

In soft, partially or fully saturated ground conditions, machine-driven tunnel construction causes short- and long-term ground deformations resulting from the disturbance of the virgin stress state of the soil and changes in the pore water conditions. These variations are, in turn, influenced by the heading face support, shield skin friction and by the gap grouting. Realistic large-scale 3D simulations are, therefore, increasingly required to investigate the interaction between machine-driven tunnel construction and the surrounding soil in order to provide reliable estimates of the expected settlements and associated risks of damage for existing structures, respectively, in particular in urban tunneling projects. If performed properly, these simulations involve complex interactions between individual components of the numerical model. The presented paper is concerned with recent advances in the process-oriented adaptive computational simulation of the excavation and steering processes in mechanized tunneling in soft soils using the finite element method. A novel automated adaptive mesh-refinement procedure is proposed to allow a refined resolution of the region of interest in the vicinity of the tunnel face during the TBM (tunnel boring machine) advancement. This procedure allows for an accurate assessment of the tunnel face stability and for the investigation of the immediate soil deformation and pore pressure changes around the tunnel. Furthermore, selected aspects of the numerical treatment - such as the stabilization of low order, two-phase, finite elements and the sub-stepping schemes inherent in the numerical integration of elasto-plastic models - are also addressed in the presentation.