Abstract: Fracturing grouting could effectively improve elastic deformation properties of soils, and thus the soil deformation induced by excavation will be greatly reduced, so it is important to study the equivalent elastic properties of the composite soils. By investigating the fracturing-grouting mechanism and some case histories comprehensively, a three-dimensional geometric model is firstly proposed for composite soils with fracturing grouting based on homogenization theory. A volume ratio and stress distribution diagram of grout-soil is developed following equivalent principle. Then the analytical solutions of the equivalent elastic modulus and equivalent Poisson’s ratio of the proposed model are derived based on transversely isotropic constitutive law. The same elastic parameters of this model for specific conditions are calculated by finite element method (FEM). At the same time, the FEM results are compared with the analytical solutions. The Flac3D is employed to predict the ground settlements of a heat-supplying tunnel using the proposed model and its analytical solutions. The predicted results are then compared with monitoring data. The study shows that: the analytical solutions of the proposed model highly agree with FEM results; the proposed model and its analytical solutions are reliable and valid for engineering practice.

Key words: fracturing grouting, composite soils, elastic modulus, Poisson’s ratio, settlement