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.
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.
Reasonable and effective ventilation plays an important role in the safety of tunnel construction. Fans are usually designed to be are capable of satisfying the maximum demand of a tunnel. During the ...tunnel construction, the actual usage of the tunnel could be considerably less than the designed fan capacity. This leads to high energy consumption and low efficiency. Therefore, a system that can analyze in real-time the tunnel environment and calculate the actual demand is required for tunnel construction. In this study, a tunnel ventilation intelligent frequency control (TVIC) system is designed based on the radial basis function neural network (RBF NN). As a type of feedforward neural network, RBF NN is used to obtain the relationship between the fan operating frequency and various pollutant concentrations, the tunnel length, and the temperature. TVIC is composed of a safety-monitoring system, control system, communication system, and variable-frequency drive (VFD) fan. It can self-adjust the frequency of the fan according to the construction environment inside the tunnel, and has been used in the Huayingshan tunnel in southwest China for a year and a half. In addition, it displays good reliability and a satisfactory capacity for tunnel environmental improvement and energy conservation. Compared with the current manual control method, ventilation system was observed to reduce electricity consumption by 42% after using TVIC.
•Tunnel ventilation intelligent frequency control system (TVIC) was developed.•Fan operating frequency was studied by the radial basis function (RBF) neural network as the algorithmic method of TVIC.•This smart ventilation system has been successful used in the Huayingshan Tunnel in southwest China for one and a half years.•Compared with the current manual control method, the TVIC reduced electricity consumption by 42%.
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