盾构千斤顶推力变化对地面变形的影响

采用三维有限元模拟盾构推进的过程 ,是研究盾构施工中土层移动的最有效的手段。本文采用三维弹塑性有限元 ,在真实模拟施工情况的基础上 ,研究了盾构推进力的变化对地面变形的影响情况。     

垂直交叉隧道的计算分析

采用三维有限元模拟盾构推进的过程 ,是研究盾构施工中土层移动的最有效的手段。本文采用三维弹塑性有限元 ,在真实模拟施工情况的基础上 ,研究了新隧道从老隧道下面垂直穿过时 ,对老隧道的变形影响情况。研究表明 ,推进力和稳定比N是影响老隧道变形的主要因素     

Wirklichkeitsnahe Brandeinwirkungen für die Planung und Nachrechnung von Tunnelschalen

Realistic fire loads for design and re‐analysis of tunnel linings Meanwhile, the development of numerical systems for the simulation of flow phenomena has reached a level, which even allows the analysis of complex scenarios such as tunnel fires, within acceptable time‐periods. On the one hand, this provides the possibility to critically question fire‐curves from standards (derived and calibrated for the general case) against the background of tunnel‐specific temperature fields. On the other hand, both temperature and smoke development as well as expected structural impairment may be assessed on a relatively realistic basis without large‐scale conflagration tests being necessary. In addition to general options of non‐linear structural analyses (i.e. utilisation of load re‐distribution and activation of additional bedding reactions) [1] the simulation‐based evaluation of fire loads particularly provides a valuable potential for the re‐analysis of existing tunnel linings. This especially applies in such cases where the calculation with conventional fire‐curves requires extensive strengthening and retrofit, whereas more favourable loading conditions may be expected by taking into account the tunnel‐specific boundary conditions. In the present paper, firstly tunnel fire accidents and the derivation of fire‐curves are generally discussed. Then, the possibilities, the theoretical background and limits of CFD modelling of fire scenarios are presented and finally, major influence factors on the thermal loading (in particular the cross‐sectional size of the tunnel) are investigated by sensitivity studies.     

盾构隧道施工多媒体监控与仿真系统

介绍了盾构隧道施工中,以光纤通信为基础,形成的多媒体监控系统的硬件组成与实现方法,在此基础上,利用PECK理论、随机介质理论等建立预测盾构施工的地表变形的数学模型,形成了三维仿真软件系统.     

CFD analysis of a realistic reduced-scale modeling equipped with axial jet fan

Typically, in the experimental scale road tunnel model, the air flow induced by ventilation system is provided by an external fan. In this paper, the authors have numerically simulated full and reduced-scale tunnel in order to evaluate the possibility to realize a reduced scale of a road tunnel model with a realistic ventilation system consisting of impulsive jet fans.In particular, two different types of longitudinal ventilation systems were considered, traditional and alternative. The last one was equipped with jet fans that have the inlet/outlet sections inclined at a fixed pitch angle (α=6°) toward the tunnel floor. The jet fan was simulated as a simple momentum source that provides a pressure rise (pressure drop) across them as a function of the outflow air velocity.The analyzed tunnel consists in a 800 m one directional bore with circular cross section 5.05 m radius; the jet fans were installed at 5.67 m from the floor. Furthermore a burning Heavy Good Vehicle (HGV), placed at 450 m far away the tunnel entrance, was considered. To simulate numerically the burning vehicle, the species transport equation combustion model with Eddy-Dissipation-Concept (EDC) model was adopted.In order to create a reduced-scale model from a full scale, Froude method was applied to preserve geometrical, kinematical and dynamical similitude. Temperature and axial velocity profiles, in different tunnel sections for both considered models (full and scaled) and ventilation systems, were provided. The numerical results showed a good agreement for the both ventilation systems.     

On the maximum smoke temperature under the ceiling in tunnel fires

Maximum smoke temperature under the ceiling in a tunnel fire was studied experimentally and numerically. Full-scale burning tests in two vehicular tunnels of length 3.27 and 1.032 km with and without operating the longitudinal ventilation system were carried out. Smoke temperatures at selected positions under the ceiling were measured under different longitudinal ventilation velocities. Two different pool fires of 1.6 and 3 MW were set up. Computational Fluid Dynamics (CFD) simulations with Fire Dynamics Simulator (FDS) version 3.10 were carried out on those scenarios. CFD predicted smoke temperatures were firstly verified by comparing with the measured values at those selected positions, and then compared with the calculated values using the empirical equation due to Kurioka et al. Fairly good agreement was achieved, though the slope of the tunnel was not considered in this empirical equation.     

A practical use of CFD for ventilation of underground works

Any underground work of a minimum length has associated a study of a ventilation system. The traditional way to calculate these systems requires the calculation of the air losses all over the installation in order to select an adequate group of fans. This paper calculates the losses in 138 situations of circular tunnels (varying tunnel diameter, air velocity and surface characteristics), by both traditional and CFD (computational fluid dynamics) means. The results of both methods are compared and adequate correlation has been observed, with CFD values constantly a 17% below the values calculated by traditional means. The paper deals with the main problems commonly encountered in the CFD use, meshing and turbulence, and shows guidance on the practical use of this numerical method. There are also shown the capabilities of the method in simulation domains including machinery of underground works: road headers, dumpers and excavators.     

Results from three models compared to full-scale tunnel fires tests

Information from full-scale fire tests are gathered and systemised. The knowledge from these tests is used as input to three different models, ranging from a simple spreadsheet model to advanced computational fluid dynamics (CFD) modelling, for calculating the temperature in the smoke layer. The deviation between the fire tests and the computed results is described and an evaluation of how this may influence the use of the models is discussed from the point of view of risk analysis.     

Numerical 3D simulation of a longitudinal ventilation system: Memorial Tunnel case

In this work, a numerical 3D simulation of a longitudinal ventilation system (LVS) is developed to analyze the fire behaviour inside a road tunnel. The numerical modelling reproduces the Memorial Tunnel, a two-lane, 853 m long road tunnel, used for experimental purposes. On this tunnel, 98 full-scale fire ventilation tests with different ventilation systems were conducted, constituting the first significant experimental approach to analyze fire incidents inside road tunnels. A total number of 24 reversible jet fans were installed in groups of three, nearly equally spaced over the length of the tunnel, and cantilevered from the ceiling of the tunnel.

The validation of a numerical model is developed in the present paper. For that purpose, the behaviour of the smoke generated during a fire incident inside a road tunnel is predicted and compared with previous experimental data collected in the Memorial Tunnel Project. The smoke evolution and the performance of the LVS is simulated with a commercial code, FLUENT, which allows 3D unsteady simulations of the Navier–Stokes equations for multispecies mixtures of gases. A sufficient mesh density was introduced for the spatial discretization in order to obtain accurate results in a reasonable CPU time. Hence, typical ratios between total number of cells and the overall tunnel length were employed in the modelling. As a result, good agreement was achieved in all the tested cases, defining an accurate methodology to predict the performance of a LVS in case of fire inside a tunnel.     

Development of energy textile to use geothermal energy in tunnels

A novel textile-type ground heat exchanger, a so-called “energy textile”, is introduced in this paper. The energy textile to be assembled in a tunnel lining is devised to function as a ground-coupled heat exchanger (GHE) to operate a ground source heat pump (GSHP) system in tunnels. A test bed of six pilot energy textile modules with various configurations was constructed in an abandoned railroad tunnel in South Korea. Long-term field monitoring was performed to measure the heat exchange capacity of each energy textile module by applying artificial heating and cooling loads on it. In the course of monitoring, the inlet and outlet fluid temperatures of the energy textile, the pumping rate, the ground temperature, and the air temperature inside the tunnel were measured continuously. Each type of energy textile modules was compared in terms of its heat exchange efficiency, which appears to be sensitive to fluctuation of air temperature in the tunnel. In addition, three-dimensional computational fluid dynamic (CFD) analyses were carried out, employing FLUENT, to simulate the field test for each energy textile module. After verification of the numerical model with the field measurement, the influence of a drainage layer on the performance of the energy textile was parametrically examined. A conventional design procedure for horizontal GHEs was used in a preliminary design of an energy textile module, taking into consideration the air temperature variation inside the tunnel over the course of one year.     

A computational study on effects of fire location on smoke movement in a road tunnel

In this work, a numerical model of tunnel fire is developed and aimed to investigate the influence of cross-sectional fire locations on critical velocity and smoke flow characteristic. It is shown that the critical velocity for a fire next to the wall is obviously higher than that for a fire in the middle or on the left/right lane. The ratio is estimated to be 1.12. The predictions of critical velocity from ‘small-fire’ models show a good agreement with that for a fire in the middle or on the left/right lane from CFD. The tunnel height at the fire location is proposed to be instead of the hydraulic tunnel height in the ‘big-fire’ model of Wu and Bakar for a fire next to the wall. The smoke moves backward in a tongue like form as the ventilation velocity is lower than the critical velocity. The back-layering length of a fire in the middle is shown to be approximate twice than that on the left/right lane under the same ventilation velocity, although they share the same critical velocity. Whereas a relatively short back-layering length for a fire next to the wall under the velocity of 2.6 and 2.7 m/s. In addition, a snaky high-temperature profile on the top wall at the initial downstream is observed for a fire on the left lane and next to the wall, and finally a steady and layered smoke flow. The likely cause of this phenomenon is subsequently explained in this study.     

An equation-based simulation environment to investigate fast building simulation

The design of innovative heating, ventilating and air-conditioning systems for energy saver buildings relies on fast and robust computer softwares able to predict the details in space and time of the indoor environment. In this paper we show the interest of having in one hand, an open and flexible environment to develop and test new models, and on the other hand, a fast simulation tool that integrates satisfactory models to quickly assess the indoor environment quality.     

数值模拟在外延阶梯型中庭空调设计中的应用

本文采用CFD软件对外延阶梯型中庭室内热环境进行数值模拟,不仅预测和验证了热环境的舒适性,而且根据模拟结果得出该建筑的空调负荷。为该类中庭的建筑形式设计、室内舒适性和节能设计提供了参考依据。