Elastic Properties of Jet-Grouted Ground and Applications

With the development of urban areas and the constant need to change or improve the existing structures, a need for creative and less destructive soil reinforcement processes has occurred. Jet-grouting is one possible ground improvement technique. The behavior of the soil improved by jet-grouting is still not well understood. In this thesis, the mechanical behavior of the injected soil is modeled in order to determine the different parameters needed for the engineering design of a soil reinforcement based on jet-grouting. At first several models are presented in order to determine the extent of the injected zone within the soil mass, based on engineering parameters (cement poroelastic properties, injection rate). A model based on an energetic balance is proposed to compute the lower bound of the injection radius. The second part of the thesis focuses on the characterization of the uniaxial compressive strength of the soilcrete created in the injected area determined in the first part. Three different methods have been adapted to the problem. A hollow sphere model has been calibrated against published data. After calibration, both Eshelby's and averaging methods proved to provide results close to the reference data. The last part of this report presents numerical studies of the pile and of a group of piles. The study of the group of piles focuses on the effect of arching between soilcrete columns to reduce the vertical settlements due to urban tunneling at the surface. It appears that the values obtained for settlements in the presence of jet-grouted columns are much less important than in usual tunneling problems (with no reinforcement).