Tunnelling and Underground Space Technology最新文献

Closure joints constructed to fill the spaces between immersed tunnel elements or between the tunnel elements and adjacent cut-and-cover tunnels are crucial for the longitudinal stability of immersed tunnels and affect the overall cost and duration of tunnel construction. To avoid the obstruction of navigation and reduce the difficulty of constructing closure joints, dry-land construction methods have been widely applied to construct closure joints for inland-river immersed tunnels, in particular using procedures involving axial dry docks. However, the traditional dry-land construction method has many inherent drawbacks. For example, the construction of underwater large-scale reinforced concrete antiretreat structures involves many underwater works, complicated construction processes, long operation time spans and high costs. Based on the Yuliangzhou immersed tunnel in China, a new dry-land construction method for closure joints of inland-river immersed tunnels based on tunnel–soil interface friction was developed to address the abovementioned problems. Considering the adverse influences of back-silting sediment on tunnel–soil interface friction, large-scale laboratory and onsite shear tests were carried out to derive the interface friction coefficients between the tunnel element base slabs and prelaid pebble foundation beds. A composite concrete steel sandwich (CCSS) water-retaining system was designed and assembled to separate the water in the dry dock from the river course. A simplified analysis method based on numerical simulations for the determination of the equivalent horizontal thrust P applied to element ES caused by the dewatering of the axial dry dock was proposed. Based on horizontal antisliding stability analyses of the tunnel elements during the axial dry dock dewatering stage, equations for the key design parameters of the new dry-land construction method were established. Through examination of the static equilibrium of the tunnel elements in the tunnel longitudinal direction, temporary longitudinal displacement constraint (LDC) structures at the immersion joints were designed. Furthermore, the following key construction techniques for the new dry-land construction method were systematically designed: installation of a CCSS water-retaining system at the entrance of the axial dry dock, water sealing at contact gaps, installation of finish-rolled screw-thread (FRST) steel bars as the LDC structures at the immersion joints, and construction of rigid connections between tunnel element ES and the cut-and-cover tunnel. Finally, onsite observation of the deformation states of Gina gaskets and monitoring of the tensile forces of FRST steel bars at the immersion joints verified the successful implementation of the new dry-land construction method, supporting the use of these techniques in closure joint design and construction for inland-river immersed tunnels.

To achieve the European Uniońs climate goals, the Norwegian transport sector has committed to decrease the Greenhouse gas (GHG) emissions by 2030. For infrastructure projects, the GHG emissions from construction must be reduced by 40 %, while the emissions from maintenance must be cut by 50%. This paper investigates how realistic the GHG emission reduction goals are, if available low carbon materials and technologies are fully adopted. To examine this, we have chosen a typical Norwegian road tunnel from which two carbon emission scenarios are presented. While tunnels represent a specific subset of road infrastructure, this study showcases that implementing sustainable practices in drill and blast tunnel construction can align with the European Union’s ambitious 2030 targets. Besides this, the findings can assist stakeholders to get advice on the environmental impacts of tunnel designs.

As urbanization progresses, the exploration and development of urban underground space resources have become imperative. Assessments of urban underground space are conducive to understanding the quantity and potential of urban underground resources that can be developed and utilized. The practice of combining urban three-dimensional geological models for suitability assessments of urban underground space is commonly used and has been proven to be effective. However, existing assessment methods struggle to automatically consider the impact of existing facilities, necessitating extensive preliminary investigation. In addition, despite the abundance of evaluation methods, there is a noticeable gap in research applying both subjective and objective evaluation techniques in tandem. To address these problems, this study introduces an innovative framework to automate the identification of existing constraints via a semantic segmentation deep learning method. In addition, a hybrid evaluation method integrating the entropy weight method, the CRITIC method, and the Analytic Hierarchy Process is proposed. This methodology not only fills a gap in existing studies by providing a comprehensive framework for urban underground space evaluations but also offers a novel approach to integrating technological advances into urban planning research. The application of this study in the Sanlong Bay area of Foshan City further demonstrates its practicality and effectiveness, showcasing a significant advancement in the field of urban underground space evaluation.

This study provides an alternative theoretical approach to analyse the mechanical behaviour of tunnels excavated in time-dependent geomaterials, considering the sequential excavation of tunnels and installation of rockbolts and elastic liner. In the theoretical analyses, the Bolted Rock Mass (BRM) is modelled as a homogeneous material but with higher stiffness. An innovative Machine-Learning-Based solver (MLB-solver) has been developed to evaluate the reinforcement ability of rockbolts for geotechnical applications. After that, the complex variable method, the Laplace transformation technique, and the extension of the correspondence principle, combined with the compatibility and boundary conditions, have been employed to obtain the analytical solutions for stresses and displacements at the rock-support and support-support interfaces. Furthermore, the analytical predictions have been validated by monitoring data from the Lyon-Turin Base Tunnel. Parametric analyses are conducted to investigate the influence of rockbolt length and installation time on tunnel behaviour. Meanwhile, the proposed theoretical solutions have been also applied to analyse tunnel stability. This study offers a new and efficient method for the preliminary design of supported tunnels.

The Peck formula is widely used to predict subsurface settlement in tunnel excavation without freezing techniques. However, predicting surface uplift during tunnel construction with artificial ground freezing is still a challenge. This investigation introduces a groundbreaking methodology by creatively inverting the Peck formula. By integrating the inverted Peck formula with the principles of plane freezing theory and considering stratum constraint conditions, we’ve developed a time-varying model to quantify the volume of stratum frost heave and the subsequent surface uplift. Through a meticulous back-analysis coupled with maximum likelihood estimation, this approach enhances the precision in gauging the extent of the frost heave mound, thereby improving the accuracy and simplicity of predicting surface uplift deformation in the tunnel construction process employing ground freezing. The robustness and credibility of this innovative approach are substantiated through an exhaustive comparative analysis juxtaposed with empirical engineering monitoring data and calculations based on the stochastic medium theory. The outcomes demonstrate that the proposed inverted Peck formula excels in its explicit clarity and practical relevance, more closely aligning with the empirical data on surface uplift than predictions derived from the stochastic medium theory, thus offering enhanced predictive performance. This study provides a novel theoretical model for anticipating surface uplift deformations in tunnel construction endeavors using ground freezing techniques, delivering valuable insights and a promising predictive tool for both engineering professionals and academic researchers.

Transport infrastructure projects frequently encounter challenges such as schedule delays and cost overruns, leading to substantial misallocation of public or private resources. These issues are often exacerbated by uncertainties in time and cost estimation outcomes. To address this, various models have been developed in recent years to enable probabilistic estimation for tunneling projects, considering uncertainties. However, the impact of uncertainties on the critical path and its implications on time and cost estimations have not been discussed explicitly and in detail for network underground structures encompassing multiple construction paths. In this study, we update the KTH time and cost estimation model using the Markov Chain Monte Carlo (MCMC) method. This updated model enables simultaneous round-by-round construction simulation across all paths in network underground structures. Consequently, it accommodates uncertainty in the critical path and its influence on time estimation outcomes. Additionally, the updated model introduces an innovative technique to model geological uncertainties along tunnel routes, thereby contributing to the field’s diversity. Practical application of the updated model is showcased using the Uri Hearace tunnel as an illustrative example. The paper also delves into the practical implications of the findings from a decision-maker’s standpoint, as well as discussing the model’s limitations.

Traffic vibration of roads, trains and metro system is increasingly influencing normal life and facility operation in large cities, as population grows and infrastructures get more congested. Aiming to assess the impact of ground-borne vibrations nearby elevated traffic system on a tunnel housing sensitive scientific in struments, this paper employed centrifugal model tests and numerical simulations to analyze the attenuation trending of vertical vibration propagating from the pile foundation supporting the traffic system and vibratory response of the tunnel model, as well as the passive damping effects of a rubber isolation layer in tunnel structure. Model tests were carried out both in saturated sandy soil layer and dry one, under individual pile vibrations. Results from centrifugal tests indicated that vertical vibration energy decreases with increasing propagation distance, with more rapid attenuation in saturated sands compared to dry sands. Comparison within frequency domain of the vibration shows that high-frequency components attenuated faster than low-frequency ones in the ground, and in the 10–50 Hz range, vibrational energy at the tunnel invert was significantly lower than at the crown, with saturated sands exhibiting lower vibrations than dry sands. However, in the 50–100 Hz range, vibrations at the tunnel invert amplified, with saturated sands exhibiting higher vibrations than dry sands. A 5 mm thick rubber isolation layer was shown to reduce vibrations at the center of the tunnel base between 10–60 Hz in saturated sandy soils. Numerical simulations supported the experimental results and further investigated the impact of soil damping ratio and dynamic shear modulus on vibration propagation. An increased damping ratio significantly reduced high-frequency vibrations and vertical acceleration FRF values. A higher dynamic shear modulus led to decreased soil acceleration response under vibration, though the effect diminished with higher excitation frequencies. This integrated experimental and numerical study provides valuable insights for optimizing vibration reduction strategies in tunnel construction, with potential applications to similar engineering projects.

The paper focuses on the prediction of tunnelling-induced settlements in greenfield conditions. The main components of ground deformation are investigated with approaches based on both empirical and numerical solutions. In particular, the study analyses five well documented case histories of shield-driven tunnels bored in coarse-grained soil deposits and compares the predicted and measured settlements.

A specific approach for FEM-2D modelling of soil-shield interaction (called “Strain Applied Method”) has been implemented and its potential for the prediction of the settlement trough has been discussed. The analyses were performed for the green field conditions with the Finite Element software Plaxis. The mechanical behaviour of the soil has been modelled by both the usual linear elasto-plastic model (Mohr-Coulomb, MC) and the advanced Hardening Soil model with small strain stiffness (HSs). The comparison of results shows that the settlements calculated by the HSs model are generally in better agreement with the field measurements. Then, the analysis has been focused on the volume loss obtained for the five case histories, finding some significant correlations between volume loss and the specific parameters required by the proposed FEM-2D model. The predictive capabilities of the 2D model, with parameters estimated by specific correlations, were demonstrated by applying the proposed method for two new case histories, not included in the initial set utilized to find the correlations.

Fire-induced spalling in concrete is a serious issue in tunnel lining design because it can reduce the load-bearing capacity of the tunnel and the cross-section area of the tunnel lining. The adverse consequences of concrete spalling can cause serious damage to the tunnel lining or even failure occasionally. Hence, concrete spalling at elevated temperatures particularly explosive spalling must be properly assessed by considering it as a crucial factor for fire resistance in concrete tunnel lining designs. In the last several years, there has been a surge of scientific studies aimed at explaining why concrete spalls when exposed to fire. Despite these attempts, a current evaluation method that can reliably forecast the average depth of spalling of concrete tunnel lining has not yet been developed, and a comprehensive analysis of this phenomenon has not been completed. Many areas of structural engineering have benefited from the use of machine learning, but no one has yet attempted to use it to predict the spalling depth of concrete tunnel lining. Most sophisticated techniques in machine learning such as ensemble learning approaches have not been adopted. This study also addressed this issue by developing a database of 415 spalling test results under 16 input variables to provide predictions about the spalling depth of concrete tunnel lining using ensemble learning approaches such as Random Forest (RF), Categorical gradient boosting algorithm (Catboost), Light gradient boosting algorithm (LightGBM) and Extreme gradient boosting algorithm (XGBoost). This research developed a novel machine learning-based framework to predict the spalling behaviour in tunnel lining exposed to fire. Based on the conclusions, XGBoost demonstrated the highest performance in predicting spalling depth in concrete tunnel linings.

The Beishan Underground Research Laboratory serves as a crucial experimental platform for the geological disposal of high-level radioactive waste in China. To investigate the impact of blasting vibrations generated by the drill and blast method on the ramp entrance section of the laboratory, the blasting vibration signals of the ramp entrance section were analysed, and the distribution characteristics of the vibration velocity and dominant frequency were obtained. By using the wavelet packet transform, the velocity and energy features within the frequency band of the blasting vibration signals were successfully extracted. The calculation formulas for explosive vibration velocity and dominant frequency were derived and verified utilizing dimensional analysis, in accordance with the Equivalent Elastic Boundary theory. The results show that the vibration velocity is highest at the floor of the ramp, lowest at the roof, and intermediate at the sidewall. Variations in the direction of the vibration velocity were also observed at these locations. The blast vibration frequencies at each location are concentrated in the range of 0∼300 Hz, within which the blast vibration velocity and energy tend to decrease from the floor to the roof. However, an increasing trend is observed in some frequency bands within 100 Hz, which requires attention. The derived formulas for the blasting vibration velocity and dominant frequency, except for the calculation deviation of the dominant frequency at the sidewall, have high accuracy, with a R²>0.8. The calculation error of the dominant frequency at the sidewall may be due to the differences in rock mass vibration stiffness, which requires further verification. These research findings provide important guidance for the field construction of the Beishan Underground Research Laboratory and offer valuable references for similar projects in the future.