Abstract
During the construction of the above-crossing tunnel, the surrounding rock of the existing tunnel will be disturbed in different degrees due to the different spacing between the upper tunnel ...and the existing tunnel. In order to study the regular pattern between the surface deformation of the existing tunnel surrounding rock and the tunnel spacing, the surrounding rock deformation of 10 groups of existing tunnels with different spacing is studied by numerical simulation based on the project of the upper loop section of Chongqing rail transit line 9. The results show that the uplift deformation of the vault of the existing tunnel will be caused by the construction of the upper double-track tunnel, and the final deformation of the existing tunnel is in the shape of “M“. The maximum displacement of the existing tunnel decreases first and then increases with the increase of the transverse distance of the upper crossing tunnel, but the maximum displacement of the existing tunnel does not change much; As the vertical distance between the new tunnel and the existing tunnel increases, the maximum displacement of the existing tunnel decreases linearly within the 3L vertical distance. It gradually stabilized after 3L, indicating that the existing tunnels beyond 3L are almost unaffected by new tunnels.
The construction of undersea tunnels is an extremely risky endeavor that is vulnerable to water seepage and gushing due to the high water pressure, complex geological conditions, and pore water ...trapped in unstable rocks. This risk can lead to the collapse of tunnels under construction and disastrous consequences of fatalities and injuries as well as project delays and financial losses. The current risk management practices for tunnel construction projects in China are static and rely on the subjective judgement of experts and practitioners and do not incorporate real-time monitoring data during the construction process at this time. This paper presents a new method and system to assess and manage the risks during the construction process by coupling the risk management system and the quality management system and integrating jobsite monitoring data, design data, and environmental data. In this new method and system, the risk factors are categorized into (hu)man, material, machine, method, and environment, or 4M1E, and are quantitatively measured. The Dempster-Shaffer (D-S) theory was adopted in this method to both fuse the 4M1E data and to compute the aggregate risk index. This new method and system was tested during the Xiamen Metro Line No. 3 project when a shield machine cutter accident occurred. The results show that, before the accident, the individual risk measures in all five dimensions (4M1E) and the aggregate risk index were extremely high, which clearly illustrated the feasibility and capability of the newly developed method and system.
•Risk management system and quality management system are coupled for quantitative risk ranking.•Jobsite monitoring data, design data, and contextual data are integrated for risk assessment.•Risk factors are categorized into (hu)man, material, machine, method, and environment, or 4M1E.•The combination of D-S evidence theory and fuzzy method for fusing heterogeneous data.•Validation through a real shield machine accident in a cross-sea tunnel project.
Massive and ambitious underground space development projects are being undertaken by many countries around the world to decongest megacities, improve the urban landscapes, upgrade outdated ...transportation networks, and expand modern railway and road systems. A number of these projects, however, reported that substantial portions of the excavated debris are oftentimes naturally contaminated with hazardous elements, which are readily released in substantial amounts once exposed to the environment. These contaminated excavation debris/spoils/mucks, loosely referred to as “naturally contaminated rocks”, contain various hazardous and toxic inorganic elements like arsenic (As), selenium (Se), boron (B), and heavy metals like lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn). If left untreated, these naturally contaminated rocks could pose very serious problems not only to the surrounding ecosystem but also to people living around the construction and disposal sites. Several incidents of soil and ground/surface water contamination, for example, have been documented due to the false assumption that excavated materials are non-hazardous because they only contain background levels of environmentally regulated elements. Naturally contaminated rocks are hazardous wastes, but they still remain largely unregulated. In fact, standard leaching tests for their evaluation and classification are not yet established. In this review, we summarized all available studies in the literature about the factors and processes crucial in the enrichment, release, and migration of the most commonly encountered hazardous and toxic elements in naturally contaminated geological materials. Although our focus is on naturally contaminated rocks, analogue systems like contaminated soils, sediments, and other hazardous wastes that have been more widely studied will also be discussed. Classification schemes and leaching tests to properly identify and regulate excavated rocks that may potentially pose environmental problems will be examined. Finally, management and mitigation strategies to limit the negative effects of these hazardous wastes are introduced.
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•Excavated rocks from underground/tunnel projects contain hazardous elements.•Arsenic, selenium, boron, & heavy metals are leached out from excavated debris.•Sulfides/oxides & soluble salts are important sources of inorganic contaminants.•Oxidation, dissolution, precipitation, & sorption control contaminant mobilities.•Existing management strategies for naturally contaminated rocks are unsustainable.
The critical current of a superconductor can be different for opposite directions of current flow when both time-reversal and inversion symmetry are broken. Such non-reciprocal behaviour creates a ...superconducting diode and has recently been experimentally demonstrated by breaking these symmetries with an applied magnetic field or by the construction of a magnetic tunnel junction. Here we report an intrinsic superconducting diode effect that is present at zero external magnetic field in mirror-symmetric twisted trilayer graphene. Such non-reciprocal behaviour, with sign that can be reversed through training with an out-of-plane magnetic field, provides direct evidence of the microscopic coexistence between superconductivity and time-reversal symmetry breaking. In addition to the magnetic-field trainability, we show that the zero-field diode effect can be controlled by varying the carrier density or twist angle. A natural interpretation for the origin of the intrinsic diode effect is an imbalance in the valley occupation of the underlying Fermi surface, which probably leads to finite-momentum Cooper pairing and nematicity in the superconducting phase.A superconducting diode effect is observed at zero magnetic field in twisted trilayer graphene. This suggests that time-reversal symmetry is intrinsically broken and leads to pairing between electrons with non-zero centre-of-mass momentum.
While Artificial intelligence (AI) has been successfully applied in assessing geotechnical risk, such methods heavily rely on data quality to achieve satisfactory performance, and their results ...hardly can be interpreted due to their opaque design. With this in mind, this paper aims to address the following research gap: How can we accurately model geotechnical risks using limited data and domain knowledge, and efficiently explain the results of AI model? We develop a physics-guided transfer learning (PGTL) model to enhance the explainability and accuracy of geotechnical risk modeling. With the help of a physical model that simulates the tunnel excavation, a physics-guided dataset with 1000 samples is established and used to train a deep neural network. On these bases, transfer learning is adopted to fuse the features of physics mechanisms and monitoring data, constructing an explainable prediction model of geotechnical risk. To further support risk decision-making, feature relevance techniques are employed to assess the contribution of input parameters to risk. A shield tunnel construction in Wuhan is selected as a case to validate the effectiveness of the proposed method. The PGTL exhibits a more promising accuracy with R2 of 0.777 in contrast to three popular machine learning approaches, and provides insights into parameters that significantly induce risk, enhancing site managers’ understanding of tunnel construction and being conducive to tunnel safety.
•A novel explainable artificial intelligence approach for geotechnical risk modeling is proposed.•Incorporate predefined physical guidance to machine learning to enhance data’s feature and provide in-model explainability.•Utilize Model-agnostic feature relevance to provide post-hoc explainability without sacrificing predictive ability.•A real tunnel construction in Wuhan, China is taken as a case study for illustration.
In the above article <xref ref-type="bibr" rid="ref1">1 , an esteemed author was inadvertently excluded. Qingxue Huang has been appropriately added to the end of the author list.
A large nonlinear optical (NLO) coefficient and a wide band gap are two crucial but contradictory parameters that are difficult to achieve simultaneously in a single infrared (IR) NLO compound. A ...salt‐inclusion chalcogenide (SIC), LiLiCs2ClGa3S6 (1), was prepared that presents a nanosized tunnel framework constructed from monotype chalcogenide tetrahedra. Highly oriented covalent GaS4 tetrahedra in the host lead to a moderate second harmonic generation response (0.7 AgGaS2), and ionic guests effectively broaden the band gap to the widest value (4.18 eV) among all IR NLO chalcogenides, thereby achieving a remarkable balance between NLO efficiency and band gap.
The salt‐inclusion chalcogenide LiLiCs2ClGa3S6 is presented, which features a 3D framework composed of Ga3S6 nanosized tunnels. Introduction of an ionic guest to the covalent chalcogenide host produces a material with a moderate nonlinear optical (NLO) coefficient and an ultrawide band gap (Eg). These characteristics are promising for the development of infrared (IR) NLO materials.
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