Urban tunnels in soil: Review of current design practice in Brazil (original) (raw)
Construction strategies for a NATM tunnel in São Paulo, Brazil, in residual soil
Underground Space, 2021
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Geotechnical Aspects of Underground Construction in Soft Ground, 2012
Current design practice for urban tunnel construction in soft ground as perceived worldwide is reviewed and discussed. The review is based on answers to a questionnaire prepared and sent out by a TC204 working group in 20 I O to practitioners involved in the design or in the design supervision of tunnelling projects. The results of this investigation are carefully considered to identify trends and needs for development.
Establishing sustainable strategies in urban underground engineering
Science and Engineering Ethics, 2004
Growth of urban areas, the corresponding increased demand for utility services and the possibility of new types of utility systems are overcrowding near surface underground space with urban utilities. Available subsurface space will continue to diminish to the point where utilidors (utility tunnels) may become inevitable. Establishing future sustainable strategies in urban underground engineering consists of the ability to lessen the use of traditional trenching. There is an increasing interest in utility tunnels for urban areas as a sustainable technique to avoid congestion of the subsurface. One of the principal advantages of utility tunnels is the substantially lower environmental impact compared with common trenches. Implementing these underground facilities is retarded most by the initial cost and management procedures. The habitual procedure is to meet problems as they arise in current practice. The moral imperative of sustainable strategies fails to confront the economic and political conflicts of interest. Municipal engineers should act as a key enabler in urban underground sustainable development.
Geomechanics and Engineering, 2018
Terrace deposits are often encountered in portal areas and tunnels with low overburden. Those deposits exhibit a great mechanical and spatial heterogeneity and a very high stiffness contrast within the ground. Terrace deposits are challenging to excavate, and difficult to characterize. Lessons learned and experiences and challenges encountered during tunnelling in terrace deposits on the Bogota-Villavicencio road (central-east Colombia) are presented. Considering that samples for laboratory testing are almost unfeasible to obtain from such deposits, and laboratory tests may not be representative because of scale effects, this document presents the approach taken for their characterization during the design stage and its posterior validation performed during the construction stage. Lessons learned suggest that based on numerical simulations, laboratory testing and tunnel system behaviour documented, in several tunnels on the Bogota-Villavicencio road, where terrace soil deposits were found, an observational approach allows the engineer to optimize the excavation and support methods for the encountered ground conditions, resulting in a more economic and safe construction.
1-G Model Tests of Tunnels with a Surrounding Cement-Treated Soil Ring
Japanese Geotechnical Society Special Publication, 2016
The construction of large diameter tunnels can be challenging, especially in soft soil conditions. Stability intervention by means of ground improvement has been identified as a possible method to allow for the safe construction of such tunnels. A 1-g physical model study of the stability of a tunnel with a cement-treated soil layer surrounding it, along with related failure loads and mechanisms, is reported here. The failure mechanism of such tunnels is found to be very different from conventional tunnels with no ground improvement as cement-treated soil is very brittle. Failure occurs locally, with cracks developing in the tensile region in the cement treated layer. These cracks consistently occur at the crown, springline and invert, over a range of improved soil layer thickness-to-tunnel diameter (t/D) ratio. These cracks are also distinctly flexural tensile in nature. Prior to the onset of cracking, the deformation of the tunnel is minimal. This in turn results in a negligible settlement trough. This implies that caution is needed on the use of ground movement as a measure of the strength mobilization, owing to the lack of warning signs. The stability of such tunnels is found to be related to the t/D ratio and strength of the improved soil layer, while the significance of the unimproved surrounding soil is found to be minimal. This leads to the formulation of a new stability equation.
This second report by the ITA Working Group on General Approaches to the Design of Tunnels presents international design procedures [or tunnels. In most tunnelling projects, the ground actively participates in providing stability to the opening. Therefore, the general approach to the design o[ tunnels includes site investigations, ground probings and in-situ monitoring, as well as the analysis of stresses and de[ormations. For the latter, the different structural design models applied at present-including the observational method-are presented. Guidelines [or the structural detailing of the tunnel lining and national recommendations on tunnel design are also given. It is hoped that the information herein, based on experiences [rom a wide range o[ tunneUing projects, will be disseminated to tunnel designers throughout the world. R~sum~-Le groupe de travail AITES sur le dimensionnement des tunnels prbsente ici son deuxibme rapport. En rassemblant toutes les in[ormations, qui btaient accessibles entre les pays sur le dimensionnement des tunnels, nous espbrons, que les expbriences gagnbes sur beaucoup de projets des travaux souterrains seront propagbes dans tout le monde. Parce que le sol participe d'une grande partie fi [ournir des moyens de stabilitb pour des ouvertures souterraines, des mbthodes de dimensionnement comprennent aussi bien les investigations sur le chantier, les essais laboratoires et la surveillance pendant le progrbs du travail que l'analyse des contraintes et des db[ormations. Concernant ce dernier point, des modbles de dimensionnement di[]brents et actuellement appliqubs sont prbsentbs, y compris aussi la mbthode d'observation. Recommendations pour les dbtails de rev~tement et quelques recommandations nationales sur le dimensionnement des tunnels achbvent ce rapport.
Geotechnical behaviour of an instrumented urban tunnel built under difficult soft soil conditions
A shallow urban tunnel for public transportation, built in difficult subsoil conditions with EPB tunnel boring machine, was instrumented to monitor its geotechnical behavior during construction. The parameters that define soil response were measured before, during and after the construction process. Herein the instrumentation used for the tunnel is described, as well as the implementation of new measurement systems. Relevant charts are shown. Immediate tunnel deformations were monitored and used to verify the shield tunneling process. Using the gathered data, correlations were developed to assess the confining influence on the surrounding soil and to describe the stress state during TBM advance. Subsidence on nearby buildings was appraised and related to the grouting support effect. Relevant conclusions regarding instrumentation, grouting and soil subsidence are provided.
Applied Sciences
The project proposal for the Desierto de los Leones tunnels in the Poetas Highway in Mexico aims to improve the excavation and support systems and evaluate the safety levels during construction. The design is based on geological and geotechnical information from the original project and can be approached using various methods, including numerical simulations. The article includes a summary of the lithological characteristics, a reinterpretation of geotechnical properties, a description of new construction procedures, and the results of calculations using the finite data differences method. The proposed project aims to improve the safety and stability of the tunnels through advanced construction technologies and adapted procedures, generated by a redesign and the scientific application of new techniques developed for this project.
Soil Conditions and Shield Tunneling Viability for Bogotá Metro Line 1
Ingeniería e Investigación
Bogotá, the capital city of Colombia, has experienced a critical situation regarding its public transport and road network condition. Unfortunately, the city has lacked an analytical long-term evaluation with regard to transport planning and infrastructure that is able to meet the growing demand. The metro system has been planned for more than half a century, and the existing soil investigations have not been fully used to evaluate the feasibility of building a metro in Bogotá’s subsoil. In order to estimate the construction viability of an underground system in the city, the authors studied the ground conditions along the alignment of Metro Line 1, as proposed in 2014. This research brought forward the stratigraphic profile of the first 6,6 km of the alignment. The ground displacements induced by tunneling were estimated by means of a finite element analysis, and the results are presented in this paper along with their significance. The results forecast surface settlements lower th...
Tunnels design and geological studies
Tunnelling and Underground Space Technology, 2019
Geologic conditions are among the greatest sources of unknowns prior to actual construction of underground excavations, especially for deep tunnels in rock. These unknowns usually exist in inverse proportional to the amount, nature and quality of the geotechnical investigations. Nevertheless, the adequacy of a site investigation program cannot be measured by cost alone. Over the past two decades the authors have analysed the investigation strategies followed along several projects weighing the cases of success or failure that finally means the ratio between foreseen, unforeseen and unforeseeable conditions as experienced after construction. In most of the cases, also after expensive investigation campaigns, the absence of a rigorous preliminary field survey left many off-ramps along the diagnostic pathway, leading to a wrong "diagnosis, misdiagnosis or delayed diagnosis". All the collected data must be interpreted inside a robust conceptual framework that in Geology primarily comes from field surveys, today enhanced by new tools and methodologies for investigating and modelling.
Urban Underground Space Development
2020
The worldwide trend of increased urbanization demands for more space for setting up buildings and transport systems so as to meet the needs of the population. Population rise leads to an increased demand for reliable infrastructure, nowadays combined with a need for increased energy efficiency and a higher environmental awareness of the public. The use of underground space can help cities meet these increased demands for infrastructure and transport systems with the same facilities that are provided on the surface. This study deals with the various construction techniques of tunnels, a study on the development of major underground transport systems, a comparative study on urban underground space planning system between China and Japan, the major underground developments undertaken in India and, challenges faced during construction.
Metro Santiago – Building an urban tunneling industry from the ground up
2007
Santiago's Metro construction started in the early 70s with the use of extensive cut-&-cover tunnel methods. This type of construction was further used in the 80s, causing major disruptions in the urban surface and strong public opposition. This situation and Metro S.A. key decision to seek for fastest, more efficient and less disruptive construction alternatives, lead to the first mined tunnel experiment under a public Park in 1994. That successful trial tunnel demonstrated the feasibility and benefits of mined tunneling and bestowed Metro S.A. the required confidence to give priority to mined construction in its future projects. Following this decision, and boosted by the continuous and massive array of new subway projects developed in the following decade, a brand-new urban tunneling culture and industry surged in Santiago de Chile. This paper presents this historical evolution, addressing the most relevant landmarks along this way so far.
Erkennen geotechnischer Vorgänge an der Ortsbrust als Schlüssel zum erfolgreichen Tunnelvortrieb
Geomechanics and Tunnelling, 2021
When tunnelling with a TBM (Tunnel Boring Machine) in rock and soil, mostly the machine is described and often reduced to a slogan. Such descriptions say little about geotechnical processes at the tunnel face that are key to the success of tunnel driving and must be considered when selecting a tunnelling system. In soil tunnels the tunnel face must be safely supported and extracting material must be possible. For a slurry shield the slurry must not escape and pressure must act on the face. In the literature mostly bentonite content is considered. With an Earth‐Pressure balance machine the soil has to have characteristics that it can be remoulded and transformed in a mass of adequate consistency with mechanical means, adding water and additives such that this mass can support the face and be extracted. Long‐term experience shows that the fine content and polymers are also important factors. Flow channels (pores) in open gravel may be clogged, and the face supported by seepage forces....
Innovative tunnelling construction methods in urban areas (Discussion Leader)
Recent innovations in yield-control support systems are allowing contractors to increase the rate of advance when tunnelling in difficult conditions associated with severely squeezing ground. Such systems are being implemented and proven in tunnelling projects using conventional excavation methods. The Saint Martin access tunnel along the Base tunnel of the Lyon-Turin rail line is presented as a case study to illustrate some of these developments which have been implemented successfully to deal with severely squeezing conditions encountered during excavation in a Carboniferous Formation.
EVOLUTION OF CONSTRUCTION PROCEDURES FOR METRO STATIONS IN BUENOS AIRES, ARGENTINA
Buenos Aires, Argentina, is expanding it's metro network. Some 22 km of new tunnels and a number of metro stations have been constructed between 1998 and 2011, and three new lines including 20 km of tunnels are scheduled for construction in the near future. During these years, construction procedures for underground stations have achieved significant improvements that had a heavy impact on design, costs and speed of construction. Some of these improvements are described in this paper, along with a brief update of the characterization of Buenos Aires soils for NATM tunneling. RESUMEN La ciudad de Buenos Aires, Argentina, expande su red de subterráneos. Se han construido 22 km de túneles y varias estaciones entre 1998 y 2011, y se planean tres líneas nuevas incluyendo 20 km de túneles adicionales para el futuro próximo. Durante estos años, los procedimientos constructivos para estaciones subterráneas han tenido mejoras significativas, con fuerte impacto en el diseño, en los costos y en la velocidad de construcción. Algunas de estas mejoras son descriptas en este artículo, junto con una breve actualización referida a la caracterización de suelos de Buenos Aires para tunelería NATM.
Tunnelling and Underground Space Technology, 2006
Understanding, and hence predicting, the ground displacements associated with multiple tunnel constructions in soft ground (soil rather than rock) is particularly important in urban areas. It has been shown by a number of previous authors that the effect of previously strained soil above the first tunnel has an effect on the ground displacements observed above subsequent tunnels constructed in close proximity to the first. This paper describes the design, development and preliminary test results for a purpose built test tank for modelling, at approximately 1/50 scale, multiple tunnels constructed in soft clay. The tank is 1.80m long, 0.60m wide and 0.45m high (this height is doubled when the consolidation section of the tank is added). The soil is consolidated from slurry to a prescribed strength by specifying the moisture content. A water bag arrangement is used to maintain a surcharge at the soil surface after consolidation in order to produce a realistic over-consolidation ratio. The tunnels (0.08m diameter) are constructed using an augering technique, with a shield and lining arrangement that allows a consistent 'volume loss' to be produced during construction. The tank has side faces made of clear Perspex, which enables the movement of the soil close to these faces to be observed. The soil displacements are recorded using digital cameras and analysed by computer. The paper describes some of the promising initial test data and the trends observed.
Metro Santiago: Building a Tunneling industry from the ground up.pdf
Santiago’s Metro construction started in the early 70s with the use of extensive cut-&-cover tunnel methods. This type of construction was further used in the 80s, causing major disruptions in the urban surface and strong public opposition. This situation and Metro S.A. key decision to seek for fastest, more efficient and less disruptive construction alternatives, lead to the first mined tunnel experiment under a public Park in 1994. That successful trial tunnel demonstrated the feasibility and benefits of mined tunneling and bestowed Metro S.A. the required confidence to give priority to mined construction in its future projects. Following this decision, and boosted by the continuous and massive array of new subway projects developed in the following decade, a brand-new urban tunneling culture and industry surged in Santiago de Chile. This paper presents this historical evolution, addressing the most relevant landmarks along this way so far.
São Paulo Metro - developments in shield tunnelling
Geomechanics and Tunnelling, 2014
The Metro Network in São Paulo has five lines in service with a total length of 107 km in one of the most booming cities in South America with a population of over 11 million inhabitants. The network can still be considered to be in its early stages; the first line was only constructed in 1968 and is now being extended. Whilst the settlement-prone Tertiary soils under São Paulo and also the crystalline basement, with its different grades of weathering and fracturing and high abrasiveness, pose challenges for shield tunnelling, they actually represent optimum conditions for high performance shield tunnelling. The paper deals with the experience gained by operator Companhia do Metropolitano de São Paulo-Metrô, contractor Construtora Norberto Odebrecht and consultant Maidl Tunnelconsultants in the construction of the metro lines with mechanised shield tunnelling technology.