Poster (Scientific congresses and symposiums)
Hydrogeological assessment of diaphragm walls used to excavate deep shafts associated to tunnels construction
Pujades, Estanislao; Jurado, Anna; Carrera, Jesus et al.
201542nd IAH International Congress, AQUA2015
 

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Keywords :
Shaft; tunnel; retaining wall; excavation; groundwater
Abstract :
[en] Deep shafts are usually required during tunnels construction (for maintenance tasks when tunnel boring machines –TBM- are used) and/or the operation stage of tunnels (emergency exits). Generally, these shafts are constructed below the water table and by the cut and cover method. Therefore, impervious diaphragm walls are desired for two main reasons: (1) to reduce risks (stability, inflows, flooding, etc.) and outside impacts (loose of groundwater resource, holes and sinkholes, etc.) during the excavation stage of a shaft and, (2) to avoid leaks and inflows of groundwater during the operation stage once the shaft is finished. Given that defects in diaphragm walls are frequent and can relatively easy be repaired before starting the excavation stage, a useful and new methodology to assess the state of enclosures before excavation is proposed. Its use would allow to reduce impacts on groundwater (construction and operation stages) and costs in case of defects as well as to increase the safety during the construction. The groundwater response regarding different scenarios of diaphragm walls is studied numerically in order to propose a successful procedure to evaluate underground enclosures imperviousness by internal pumping tests. The scenarios consist in circular and square enclosures where the diaphragm walls are assumed as homogeneous (with numerous defects) or heterogeneous (one discrete defect). The homogeneous cases are modeled by considering different effective hydraulic conductivities, while the size and position of the single defect is varied in the simulations of heterogeneous walls. An analysis of diagnostic plots and the comparison between the expected and measured groundwater evolutions inside the enclosure, is proposed to ascertain: (1) if the diaphragm walls can be considered as homogeneous or heterogeneous, (2) the effective hydraulic conductivity of the walls (if they are homogeneous) and, (3) the position of a defect (if they are heterogeneous).
Disciplines :
Geological, petroleum & mining engineering
Author, co-author :
Pujades, Estanislao ;  Université de Liège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement
Jurado, Anna;  GHS, Institute of Environmental Assessment and Water Research (IDAEA), CSIC, Barcelona, Spain
Carrera, Jesus;  GHS, Institute of Environmental Assessment and Water Research (IDAEA), CSIC, Barcelona, Spain
Vázquez-Suñé, Enric;  GHS, Institute of Environmental Assessment and Water Research (IDAEA), CSIC, Barcelona, Spain
Dassargues, Alain  ;  Université de Liège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement
Language :
English
Title :
Hydrogeological assessment of diaphragm walls used to excavate deep shafts associated to tunnels construction
Publication date :
17 September 2015
Event name :
42nd IAH International Congress, AQUA2015
Event organizer :
IAH Italian Chapter
Event place :
Rome, Italy
Event date :
From 13-09-2015 to 18-09-2015
Audience :
International
Funders :
ULg - University of Liège [BE]
EU - European Union [BE]
Funding text :
University of Liège and the EU through the Marie Curie BeIPD-COFUND postdoctoral fellowship programme (2014-2016)
Available on ORBi :
since 21 September 2015

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