ABSTRACT
Tunneling is a complex civil engineering construction process and requires not only a thorough conception of the variations that may be expected on the soil and rock mass but also a clear perception of construction procedures. This paper presents the results of a study where the stability of the excavation and the deformations induced thereby were assessed by a finite element code and compared to the results of the monitoring programme. The excavation in question, illustrated in Figure 1, took place during the construction of Fortaleza’s underground in Brazil (Metrofor Project). It consisted of a cut-and-cover method, where 17 metres depth precast reinforced concrete panels were placed in a slurry trench. The soil profile is composed basically of a layer of fine loose silty sand with an underlying clayey sand stratum. The water level ranges from 2.0 to 4.5 m depth. The monitoring programme consisted of surveying methods and extensometers used to monitor the magnitude and rate of horizontal and vertical deformations of the structures and ground surface. Triaxial and direct shear tests were carried out in order to define soil parameters required to the numerical simulations.
