Influence of the Soil Initial Shear Modulus on the Behaviour of Retaining Walls for Deep Excavations in Bucharest – Case Studies

Initial shear modulus (G0) is an important soil parameter used in geotechnical and earthquake engineering, when modelling geotechnical structures using advanced models for the soil behaviour or when modelling the soil-structure interaction in seismic analysis. Starting from the theory of wave propagation, it is known that this parameter is obtained through in situ or laboratory tests, by measurements of the shear wave velocity of the soil. This paper presents an analysis of the initial shear modulus values obtained by seismic tests in depth, carried out during the geotechnical investigations of several projects developed by the authors in Bucharest area. The results obtained from these tests were related to the stratigraphy on site, to relate the values obtained with the geological stratums typical for the city. The further performed analysis was approaching the influence of adopting different values for the initial shear modulus, within the interval obtained from the abovementioned investigations on the behaviour of retaining walls for deep excavations in the urban area of Bucharest. The analysis of the behaviour was performed through Finite Element Method, using the hyperbolic constitutive law with account of the initial shear modulus for the soil. The results obtained in terms of efforts and deformations for different values of initial shear modulus, keeping the rest of the parameters constant, are then presented and discussed. Also, the results are compared to measurements of the deformations carried out in inclinometer casings installed in diaphragm walls and in ground extensometers installed in the ground, considering real cases.