Urban tunnels in soil: Review of current design practice in Brazil (original) (raw)
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Construction strategies for a NATM tunnel in São Paulo, Brazil, in residual soil
Underground Space, 2021
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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...