Ejecución de túneles en terreno deltaico mediante tuneladora EPB. El caso de la línea 9
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Estadístiques de LA Referencia / Recolecta
Inclou dades d'ús des de 2022
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hdl:2117/363541
Tipus de documentLlibre
Data publicació2021-10-06
EditorInternational Centre for Numerical Methods in Engineering (CIMNE)
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Abstract
The progressive increment in urban tunneling may generate significant problems. One of the main
concerns is the unavoidable ground movements generated; before, during and after the tunneling
operations. In this context, the objective of this monograph is the study of the ground movements, both
on the surface and at depth, caused by tunnel excavations using Tunnel Boring Machines (TBMs).
Within the scope of TBMs, we can distinguish between tunneling machines for hard ground and shield
machines for excavation in low-strength soils. The shield machines and, specifically, the Earth Pressure
Balance shields, are based on the principle of equilibrium between the tunnel face and the excavated soil
in the front chamber. The presence of the excavated ground in the chamber avoids from instabilities,
especially when excavating soils with low cohesion under water.
An example of EPB tunneling is the case of the Line 9 (under construction) of the Barcelona Metro.
Once the Line will be finished, it would be one of the longest lines in Europe with a total length of 47.8
Km constructed for the most part in an urban setting.
This Line 9 tunnel crosses different types of soils. This monograph specifically refers to the excavation
of Line 9 between Terminal 1 at the Prat airport and the industrial area called “Parc Logistic”. This 14
km- long section of the route is called Section 1 in the construction project of the Line 9 and corresponds
to the stretch between the stations of Terminal T1 and Parc Logístic.
The studied area is located in the Llobregat river delta and it is made up of quaternary deltaic deposits
completely excavated in soft deltaic deposits of mixed soft clays that constitute a quite uniform layer.
Tunneling is performed by two EPB machines of 9.4 m diameter.
An important monitoring system was installed not only in Section 1 but throughout the whole line as
well. The system was devoted to the measurement of the magnitude and distribution of ground
movements before, during and after the passing of the EPB.
The information on the horizontal and vertical movements, at the surface and at depth, is analyzed and
compared with empirical and semi-empirical methods available in the literature. Both the cross-section
and the longitudinal distributions are considered.
For the case of surface settlement troughs, the comparisons are made at two times related to the
excavation process. The first one, called short-term, considers the movements until the tunnel lining has
been installed. The second one, called long-term, considers the movements until the consolidation of the
ground has finished. The settlement distributions have been represented by an inverted Gaussian
distribution curve that has been adjusted using different methods. In addition, the observed settlement
troughs have been approximated by alternative empirical expressions and by equations based on
analytical solutions.
For the case of the vertical and horizontal movement distributions at depth, the same short-term and the
long-term points mentioned above have been considered. Movements at depth have been examined in
ten cross-sections (also called transverse sections) along the line, called Control Sections.
In the same way, the data recorded by vibrating wire piezometers and Casagrande open piezometers have
been analyzed and the variation of the piezometric has been plotted.
The analysis of all the data collected has allowed the comparison between the results of Line 9 Section
1 with forty-five cases of tunnels excavated not only in similar soft soils, but also in sandy soils and in
stiff clays.
Finally, two-dimensional simulation of the excavation has been carried out using the Plaxis finite
element program, using a constitutive model that includes small deformation behavior, the Small Strain
Hardening Soil. The analysis has been able to reproduce satisfactorily the observed movements both in
the short and long term, establishing a useful record for other EPB tunneling projects in similar soft
soils.
CitacióYubero, M.T.; Gens, A.; Di Mariano, A. Ejecución de túneles en terreno deltaico mediante tuneladora EPB. El caso de la línea 9. Barcelona: International Centre for Numerical Methods in Engineering (CIMNE), 2021.
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