A Simplified Method for Predicting Tunneling-Induced Ground Movement considering Nonuniform Deformation Boundary

Stochastic medium (SM) theory is a practical method in ground settlement prediction, while its nonintegrable double integral form makes the solution process complicated. A simplified analytical solution based on the SM theory is developed to predict the ground movement in tunneling excavation. With the simplified solution, the ground movement for single tunnel and twin tunnels could be predicted based on the gap parameter G and influence angle β. A feasible approach is developed to estimate these two parameters using the maximum ground settlement Smax and tunnel design parameters, including tunnel depth H and diameter R. The proposed approach can be used to predict the ground movement curve for both circular and noncircular cross section tunnels. To validate its accuracy, the results predicted by the simplified procedure are compared with those obtained by the SM theory and measured in situ. The comparisons show that the current results agree well with those obtained by the SM theory and measured in situ. The comparison of five tunnels in literature illustrates that the simplified method can provide a more reasonable prediction for the ground movement induced by tunneling.

The Ontology-Based Approach Supporting Holistic Energy-Tunnel Design considering Cost, Heat Flux, and System Feasibility

As an emerging geothermal structure, the energy tunnel has been an important part of geothermal engineering. However, the conventional methods for designing energy tunnels mostly rely on complex numerical models. Furthermore, a macrolevel multidomain collaborative design method to consider multiple areas and design indicators is unavailable. This study combined ontology and semantic Web rule language to establish the domain knowledge of energy tunnels which is an enrichment of the conventional ground source heat pump domain knowledge and develop a comprehensive decision-making tool named OntoETS for the design of energy-tunnel systems. The tool can promote the optimal design scheme with an optimal combination of multiple indexes through an analysis of the economy, heat flux, and system feasibility of the energy-tunnel system from a macroperspective by combining multiple domains. Furthermore, a case study was conducted to demonstrate the effectiveness and practicability of the developed holistic decision-making system.

Research@ZaB: Study of FDS Capabilities to Assess the High-Speed Train Impact on Pressure Pattern Within a Railway Tunnel

The “wind tunnel” approach is applied to study high-speed train aerodynamics in a railway tunnel using FDS software. The main focus of the research is on the pressure distribution along the tunnel. Proven analytical dependencies based on the experimental observations for air jet centerline velocity and flow entrainment are used to evaluate the model setup. A model verification is carried out based on the pressure drop calculations due to viscous effects where the impact of the surface roughness and the tunnel length are also considered. A sensitivity analysis is performed to evaluate changes in input FDS parameters and to explore interactions between them. It is proposed to use the standard deviation, obtained from the calculated time-averaged pressure values, to specify the appropriate numeric parameter combinations, e.g. DT and PRESSURE_TOLERANCE, considering the desired results consistency and the computational time consumed. The simulated cases with and without a train inside a tunnel provide data on the aerodynamic characteristics of the models. The obtained volumetric and cross-sectional profiles for pressure and airflow velocity distribution form the basis for an informed decision regarding the tunnel design or safety solutions, for example, defining areas under maximal and minimal pressure loads. The analysis displays the necessity to carefully manage each investigated case considering the FDS features and limitations that largely affect a model setup and calculations.

Water Inrush Risk Assessment Based on AHP and Advance Forecast Approach: A Case Study in the Micangshan Tunnel

Water inrush is a serious geological disaster in tunnel. For the effective prevention and control of the occurrence of water inrush, a static-dynamic water inrush risk assessment method is proposed by considering the Micangshan tunnel as an example. First, four possible types of water inrush phenomenon are identified based on the geological and hydrogeological conditions of the tunnel: water inrush in water-bearing cracks, fault fracture zones, karst pipelines, and karst caves. Next, evaluation indexes that affect water inrush are determined. By combining the index weight value calculated by analytic hierarchy process (AHP) with the index quantitative value, the static water inrush disaster evaluation model is established, which provides a basis for tunnel design. Finally, with the combination of the static evaluation model and advanced forecast method, a dynamic risk prediction method of water inrush is established, which provides guidance for safe construction. The results confirm that the proposed method is a reliable theoretical basis for early assessment and prediction of tunnel water inrush disasters.

Parametric Evaluation of Simultaneous Effects of Damaged Zone Parameters and Rock Strength Properties on GRC

The convergence-confinement method via the ground reaction curve (GRC) is used as the common practice of tunnel design which demands accurate determination of the stress state and material strength behavior in different zones around the tunnel section. Besides, formation of the excavation/blast-induced damaged zone (EDZ/BDZ) adds more complexity to the problem due to variation of elasticity modulus of the rock mass in this zone. As a result, advanced numerical methods via finite element/difference commercial packages or user-coded, semi-numerical techniques are required to develop the GRC, which demands a high degree of proficiency and knowledge of computational plasticity and geomechanics. In this study, a new, simple, and accurate method is proposed for prediction of GRC of circular tunnels constructed in the damaged, elastoplastic rock masses obeying softening in the plastic zone. The effects of deterioration caused by the drilling/blast in the EDZ were taken into account by assuming a reduced and varying Young’s modulus using the disturbance factor, in the form of Hoek–Brown failure criterion and the Geological Strength Index (GSI). Besides, effects of intermediate principal stress and the exponential decaying dilation parameter are taken into account thanks to adoption of the unified strength criterion (USC) as the material strength criteria. To do so, genetic algorithm (GA) via the method of evolutionary polynomial regression (EPR) is used to find a relationship between a number of 19 affecting parameters on the GRC as the input, and the internal support pressure as the target of prediction. Verification analysis was performed to verify the validity of the results using field measurements data as well as other advanced numerical studies found in the literature. Lastly, variation of the support pressure with simultaneous changes in the affecting input parameters was investigated using multivariable parametric study.

To Analyze Different Excavation Pattern in NATM Construction

Underground construction is preferable due to lack of space availability on surface in urban areas, so the underground construction is increasing throughout the world for various reasons. Tunneling in urban area is a unique challenge, these challenge can be addressed with suitable tunnel design. New Austrian Tunneling Method (NATM) has become the method of choice for tunneling in urban areas to construct underground structure such as metro station, rail crossovers, multi-track metro lines. The aim of this report is to analyze different excavation pattern such as heading, benching and invert in NATM construction in varying geological conditions by using RS2 software for determining stresses across the tunnel surrounding and to give a best suitable excavation pattern for construction of tunnel.

Influence of Lining Design Parameters on the Greenhouse Gas Emissions of Chinese Highway Tunnel Construction

To realize low-carbon design for tunnel construction, the authors explored the relationship between tunnel design and greenhouse gas (GHG) emissions. This study proposed typical design models of Chinese highway tunnels based on the lining design specifications and engineering design cases. The research modified the GHG emission calculation method based on the standard quota system. The marginal GHG emissions caused by a change of design parameters of tunnel lining were determined. The results show that the emissions from shotcrete, concrete arch wall, system bolts, and steel frames are sensitive to the change of design parameters, while steel mesh is not. As the design thickness increases, the emissions of the concrete arch wall, inverted arch, and shotcrete increase approximately linearly. The emission distributions of system bolts and steel frames under different spacing are given. Under the same longitudinal spacing condition, the emission ratio of I18 and I16 steel frames is 1.197, and that of I16 and I14 steel frames is 1.316. By defining the marginal emissions caused by the change of design parameters, this study carried out basic work for highway tunnel low-carbon designs. The research is of strategic significance for achieving energy conservation and emission reduction in the tunnel industry.