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A numerical case study on the long-term seismic assessment of reinforced concrete tunnels in corrosive environments

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第3期15卷 551-572页

作者： Maria Antoniou Antonios Mantakas Nikolaos Nikitas Raul Fuentes ETH Zurich ZurichSwitzerland National Technical University of Athens AthensGreece University of Leeds LeedsUK RWTH Aachen University AachenGermany

The paper investigates the long-term seismic behaviour of an underground reinforced concrete(RC)metro tunnel in Santiago,Chile,considering the combined effects of chloride-induced corrosion and cumulative,low-amplitude seismic shaking on the structure’s performance.The soil-tunnel response is evaluated with the aid of transient,nonlinear finite element analysis using a two-dimensional(2D)plane strain numerical model that adopts advanced nonlinear models for the simulation of soil and concrete plasticity and the dynamic stiffness behaviour.The effects of corrosion deterioration are demonstrated in terms of time-dependent loss of rebar area and cover concrete stiffness and strength.The study illustrates the influence of ageing and repeated seismic shaking on lining deformation,crack development,and the modal characteristics of the intact and degrading systems.The results indicate that multiple lowamplitude events drive the non-degrading RC tunnel beyond its elastic regime without significant structural response consequences.A noticeable impact of corrosion deterioration on the structure’s seismic performance is revealed,increasing with the number and intensity of earthquake events.Two different tunnel embedment depths are comparatively assessed.The analyses demonstrate larger coseismic section convergence in the case of the deeper tunnel,yet a less pronounced effect of ageing and successive seismic loading compared to the shallow section,which is evident in the RC lining cracks at the end of shaking.

关键词： tunnels Reinforcement corrosion Ageing Earthquakes Numerical modelling Long-term performance Concrete cracking behaviour

Challenges and Development Prospects of Ultra-Long and Ultra-Deep Mountain tunnels

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Engineering 2019年第3期5卷 384-392页

作者： Hehua Zhu Jinxiu Yan Wenhao Liang College of Civil Engineering Tongji University Shanghai 200092 China China Railway Academy Co. Ltd. Chengdu 611731 China China Railway Construction Co. Ltd. Beijing 100855 China

1. Introduction Social development has led to the placement of high standards on ultra-long and ultra-deep mountain tunnels. Disasters may be encountered during the construction and maintenance of such mountain tunnels due to high geostress, high geotemperature, high hydraulic pressure, and special adverse strata, in addition to various other problems caused by engineering activities. To deal with uncertain geological conditions during mountain tunnel construction, comprehensive geological prediction, refined monitoring, and dynamic design and construction methods based on information technology should be adopted. For the operation and maintenance of ultra-long tunnels, the concepts of dynamic evacuation rescue, active protection, energy conservation, and environmental protection should be fully embodied in order to address significant problems related to ventilation, rescue situations, and energy consumption. Moreover, integrated construction and maintenance should be carried out to achieve digital sensing and intelligent maintenance.

关键词： Mountain tunnels Challenges Development

Impact of seismic design on tunnels in rock-Case histories

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Underground Space 2017年第2期2卷 106-114页

作者： Carlos A.Jaramillo COWI North America 1300 Clay Street7th FloorOaklandCA 94612USA

The tunnel industry has considered that tunnels,especially tunnels in rock,are naturally resistant to earthquake action,including faulting,shaking,deflection and ground failure.As the number of case histories of tunnels subject to earthquake action has increased,the industry has started to recognize that,although tunnels in rock have good resistance against earthquakes generating peak ground accelerations(PGA)lower than 0.5 g,it is important to include the dynamic forces and displacements generated by seismic ground motions in the design process to obtain a more reliable design.These additional earthquake forces impact the final design,potentially requiring changes to the ground support and additional reinforcement of the concrete lining,as illustrated by case histories presented in this paper.

关键词： Tunnel tunnels Seismic design Earthquake impact Tunnel lining Ground support

Support pressure for circular tunnels in two layered undrained clay

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第1期12卷 135-148页

作者： Bibhash Kumar Jagdish Prasad Sahoo Department of Civil Engineering National Institute of TechnologyUttarakhand246174India Department of Civil Engineering Indian Institute of TechnologyRoorkee247667India

To estimate the required support pressure for stability of circular tunnels in two layered clay under undrained condition,numerical solutions are developed by performing finite element lower bound limit analysis in conjunction with second-order cone programming.The support system is assumed to offer uniform internal compressive pressure on its periphery.From the literature,it is known that the stability of tunnels depends on the overburden pressure acting over it,which is a function of undrained cohesion and unit weight of soil,and cover of soil.When a tunnel is constructed in layered undrained clay,the stability depends on the undrained shear strength,unit weight,and thickness of one layer relative to the other layer.In the present study,the solutions are presented in a form of dimensionless charts which can be used for design of tunnel support systems for different combinations of ratios of unit weight and undrained shear strength of upper layer to those of lower layer,thickness of both layers,and total soil cover depth.

关键词： Finite elements Layered clay Limit analysis Stability of tunnels

Laboratory tests to study the influence of rock stress confinement on the performances of TBM discs in tunnels

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International Journal of Minerals,Metallurgy and Materials 2011年第3期18卷 253-259页

作者： N. Innaurato C. Oggeri P. Oreste R. Vinai DITAG Politecnico di Torino Corso Duca degli Abruzzi 24 Turin Italy

To clarify some aspects of rock destruction with a disc acting on a high confined tunnel face, a series of tests were carried out to examine fracture mechanisms under an indenter that simulates the tunnel boring machine （TBM） tool action, in the presence of an adjacent groove, when a state of stress （lateral confinement） is imposed on a rock sample. These tests proved the importance of carefully establishing the optimal distance of grooves produced by discs acting on a confined surface, and the value （as a mere order of magnitude） of the increase of the thrust to produce the initiation of chip formation, as long as the confinement pressure becomes greater.

关键词： tunnels boring machines rock mechanics stress analysis

Simulation of Stress Distribution around tunnels and Interaction between tunnels Using an Elasto–plastic Model

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Journal of China University of Geosciences 2007年第1期18卷 90-94页

作者： Muya M S 何波王靖涛李国成 School of Civil Engineering and Mechanics Huazhong University of Science and Technology

This article presents a computer simulation of stress distribution around tunnels and interaction between tunnels using an elasto-plastic model. A finite element method using ANSYS software has been used for the analyses of one and two tunnels at different overburden depths with different separating distances between the tunnels. The results of numerical analyses indicate that stress distribution and stress concentration around the tunnels vary with the overburden depths. It is found that the coefficients of stress concentration for elasto-plastic medium are smaller than those for elastic one by 1.9%. Furthermore, the interaction between the two tunnels rapidly decreases with the increase of separation distance between them. In addition, for quantitatively describing the interaction between the two tunnels, a critical separation distance is introduced. The critical separation distances between the two tunnels at different overburden depths are 8 m, 12 m, and 14 m respectively. This fact is very important and essential for the design of mining tunnels and to ensure safety in tunnel engineering.

关键词： computer simulation tunnels stress distribution interaction

Interaction of Twin Circular Shallow tunnels in Soils—Parametric Study

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Open Journal of Civil Engineering 2017年第1期7卷 100-115页

作者： Faisal I. Shalabi Department of Civil & Environmental Engineering King Faisal University Al-Ahssa Kingdom of Saudi Arabia

In big and crowded cities with limited urban areas, it is sometimes necessary to build twin tunnels to overcome transportation problems. In a city like Riyadh in Saudi Arabia, tunneling becomes very essential to solve effectively traffic conjunctions and associated problems. The city started to construct big tunneling projects and it is expected in the near future to start building twin tunnels. If the design and construction process of twin tunnels are not understood and considered, damage to the tunnel lining or excessive ground surface settlement may take place. In this study, the interaction between adjacent tunnels excavated through soils in Saudi Arabia has been investigated using FE analysis and the range of the encountered soil properties. The investigation considered the effect of spacing between the twin tunnels and ground conditions on tunnel behavior. The analysis focused on the effect of constructing twin tunnels on ground surface settlement, contact pressure between lining and ground, and change in tunnel diameter. Based on the results obtained, it was observed that as the compressibility ratio, c, and spacing between tunnels decreased, the interaction effect between tunnels increased. For compressibility ratio of 0.01, the excavation of the new tunnel caused an increase in the lining deformation of the old one in the range of 0.1% to 0.3%. Furthermore, the excavation of the new tunnel leads to an increase in the contact pressure at the crown of the old one by 7% - 9%. At the spring line level, the excavation of the new tunnel had almost no effect on the far side of the old one. On the other hand, and for low compressibility ratio, the new tunnel excavation significantly affected contact pressure at the near side of the old one. For an expected tunnel life of 100 years, the results show an increase in the normalized contact pressure at the crown of the old tunnel due to the excavation of the new one in the range of 2% - 7% for compressibility ratio ranging between 0.01 - 0.1, respectively.

关键词： Twin tunnels FE Analysis Settlement Deformation Contact Pressure

Investigation and assessment on mountain tunnels and geotechnical damage after the Wenchuan earthquake

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Science China(Technological Sciences) 2009年第2期52卷 546-558页

作者： WANG ZhengZheng GAO Bo JIANG YuanJun YUAN Song School of Civil Engineering Southwest Jiaotong UniversityChengdu 610031China Department of Civil Engineering University of TokyoTokyo 1138656Japan

On May 12, 2008, a strong earthquake with a magnitude of 8.0 (Ms) struck Wenchuan town, in the eastern Sichuan area of west China. Following the earthquake on May 18, the Southwest Jiaotong University organized a damage survey team and dispatched it to the affected area for the investigation into the damage and collection of information and data. This paper outlines the findings of this investigation on the earthquake disaster to mountain tunnels and geotechnical engineering. The systematic investigation, involving geological conditions, design documents, construction and maintenance records of the tunnels, has been conducted and the degree of damage to investigated tunnels has been assessed according to the width and length of cracks, the stability of the slope above the tunnel, and the condition of the groundwater inrush. The results show that the major damage of the mountain tunnels was mainly concentrated in the tunnel portals due to widespread landslides and rockfalls, and the inner part of investigated tunnels suffered moderate damages mainly due to fault displacements. It is hoped that the information shared herein could enhance the outstanding of seismic behavior of mountain tunnels and improve seismic design and construction procedures.

关键词： damage investigation wenchuan earthquake mountain tunnels ground failures

Multiphase Flow Simulations through Tarbela Dam Spillways and tunnels

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Journal of Water Resource and Protection 2010年第6期2卷 532-539页

作者： Muhammad Abid Muftooh Ur Rehman Siddiqi 不详

Tarbela dam is one of the largest earth filled dam in the world used for power generation and irrigation purposes. Like all reservoirs the sediments inflow in the Tarbela reservoir has resulted in reduction in water storage capacity and is also causing damage to the tunnels, power generating units and ultimately to the plant equipment. This numerical study was performed to predict the flow patterns and characteristics in Tarbela dam. Tunnel 3 and 4 inlets;originally on the bed level were raised in the 3-D model and meshed. Analysis was performed using multiphase flow (water and air) for maximum inflow in the reservoir, i.e., considering summer season and discharging water through different locations, i.e., tunnels and spillways. Pressure, velocities, flow rate and free surface height results obtained were found in good agreement with the analytical and existing results where available. Results show uneven discharge through each gate due to maximum velocity near exits and overall stagnant phenomena of water within the reservoir. Maximum velocity was observed along the spillways outlet. Strong vortex motion was observed near the spillways outlet and tunnel inlets. New design of Tunnel 3 and 4 were suggested to WAPDA in order to decrease the sediment inflow and improvements in design of the spillways were suggested.

关键词： Tarbela Dam Reservoir Flow Simulation Multiphase Flow Spillways tunnels