Evaluation of the local factor of safety from m situ inclinometer and vane test data

Abstract

Recent cases of total and partial foundation failures of soft soils during construction of tall embankments such as the case of the railroad overpass at Azambuja and waste fills constructed on the grounds of the EXP098 in Lisbon, outstand the need to develop new methods based on in situ data to estimate stress-strain parameters and local factors of safety. Toe expansion of the city of Lisbon to zones where the foundation soils are mainly composed of soft sensitive soils, with significant thickness (over 10 m), made it important to develop such methods. Salgado (1995) proposed a new procedure to estimate the distribution of the horizontal shear strain, YJt, from inclinometer field data and Carvalho (1997) proposed news procedures to estimate: i) stress-strain soil parameters, including the shear modulus, G, from in situ vane tests; ii) values of the local factor of safety based on 1'h and G. ln this paper these new methods are checked against both measured field data and the rei.'111.ts of two dimensional (2D) finite element analysis of the total and partial failures developed at the Azambuja site.