3D Analysis of Ground Displacements Due To The Construction Of Lisbon Underground

Maranha, J.R. (LNEC) | das Neves, E. Maranha (LNEC)

OnePetro 

ABSTRACT: A 3D mathematical modelling of a tunnel construction using an EPBS shield type machine is presented. The excavated soils are soft and hard clays under phreatic level and the different construction phases, including the grout injection, are simulated. The calculation results, namely the surface settlements, agree quite well with those measured in situ, thus encouraging further research related with this kind of approach. INTRODUCTION It is well recognised that the construction of large diameter tunnels at relatively low depths may generate significant movements at ground surface. If those tunnels have to be build in urban areas founded on soil formations, important problems related with safety and serviceability of the buildings under consideration will certainly arise, mainly when those soils have poor geotechnical characteristics and the urban area in question is, for instance, a historical centre of a large city. It is thus natural that ever since a greater attention have been focused on the development of procedures allowing the prediction of ground movements associated with the opening of tunnels, with emphasis on surface settlements. Those procedures encompass semi-empirical methods as well as calculations based on numerical methods of solution of boundary value problems making use of different constitutive laws. The first gave invaluable contributions to the design approach to this type of problems (Peck, 1969; Sagaseta and Oteo,1974; OÕReilly and New, 1982), still with large use even at present. But, as could be expected, there is a growing tendency for the application of numerical methods. In the latter case it must be pointed out that the analyses are in the main bidimensional (Benmebarek et al., 1998; Hara et al., 1996; Chiorboli and Marcheselli, 1996) and as such, can hardly take care of the important influence of both the tridimensional effects and the specific construction techniques.

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