Tropical residual clays with a highly porous structure react to the stress changes induced by tunneling in such a way that surface settlements can be larger than crown-level settlements along a tunnel axis. This behavior, which is not readily simulated by most numerical analyses, was also observed in the Paraiso tunnel, built for the Sao Paulo Metro, Brazil. This is a shallow tunnel driven through porous clayey soils by the sequential method. Detailed results of field monitoring are presented and discussed. 3D finite-element analyses that allowed a detailed simulation of the construction sequence have been carried out, considering two distinct constitutive models for the soil: a simple elastic-perfectly-plastic Mohr-Coulomb model, and the elastoplastic model developed by Lade. The results of these analyses are compared with the observed behavior as well as with the results from a plane strain finite-element analysis. It is shown that only the 3D finite-element analysis coupled with the more sophisticated soil constitutive model provides a full reproduction of field performance, with particular relevance for the deformations in the soil mass over the tunnel.
[1]
Robert J. Mair,et al.
SUBSURFACE SETTLEMENT PROFILES ABOVE TUNNELS IN CLAYS
,
1993
.
[2]
D. Potts,et al.
SUBSIDENCE ABOVE SHALLOW TUNNELS IN SOFT GROUND
,
1977
.
[3]
Poul V. Lade.
Stress-strain theory for normally consolidated clay
,
1980
.
[4]
A. Guenot,et al.
Analysis of convergence behind the face of a tunnel : Tunnelling 82, proceedings of the 3rd international symposium, Brighton, 7–11 June 1982, P197–204. Publ London: IMM, 1982
,
1983
.
[5]
Alfreds R. Jumikis.
Introduction to soil mechanics
,
1962
.
[6]
Jorge G. Zornberg,et al.
Numerical Analysis of a Tunnel in Residual Soils
,
2002
.