Soutenance de thèse : Nour EL SOUWAISSI

Rheological and geomechanical studies on excavated soils by Earth Pressure Balance Machine : metro 16-1, Grand Paris Express

Doctorante : Nour EL SOUWAISSI

Laboratoire INSA : GEOMAS

Ecole doctorale : ED162 : Mécanique, Energétique, Génie Civil, Acoustique de Lyon

Earth pressure balance machine (EPBM) is the excavation technique responding to the technical construction complexity of the future line 16-1 of the Grand Paris Express project. Its principle is based on the capacity of the excavated ground to transmit the forces needed to counterbalance the earth and water pressures of the working face. To overcome uncertainties in soil related to the clogging potential or the high permeability, additives are injected into the soil; on the cutting wheel, in the excavation chamber and/or in the screw conveyor. Their role is to modify the hydromechanical and rheological parameters of the soil.
The literature developed experimental tests to deduce the optimal foam parameters. These tests mainly include the study of the bubble size of foams and their stability with time, and the analysis of the flow behavior of the conditioned soil with foam.
This research investigates the physical characteristics of several foams used in this project, by summing up the tests mostly used in foam characterization, and links them to their chemical properties. In addition, this work studies the impact of foams on several types of real soil and deduces the optimal quantities by the mean of experimental tests and in-situ data analysis.
This research deals with real soils that limit the quantity of sampling. Therefore, the experimental tests consist on studying the flow behavior of the conditioned soils with foams by the mean of tests requiring small quantity of samples; a mini cone developed in this project, rheological tests and microstructure observations. The results are compared to the real excavation data. This data analysis consist on statistically studying the impact of foams on the mechanical parameters of EPBMs in function of the type of soil.
Consequently, a correlation between soil, foam and conditioned soil with foam is deduced at different levels: micro, meso and macro (real) scales.