MECHANISM ANALYSIS OF STRUCTURED LOESS FRACTURING GROUTING

Based on the theory of plastic mechanics and large-deformation, this paper analyzes the mechanical mechanism of fracturing grouting in loess area. It treats the early phase of grouting as the problem of cavity expansion in infinite soil and divides the stress distribution due to the cavity expansion in soil into three zones: elastic zone, plastic zone and damage zone. Combined with the modified Cam-clay model of structural loess, the deformation following small deformation assumption in elastic zone and large deformation assumption in plastic and damage zones is taken into consideration. According to the stress equilibrium equation and stress-strain continuous boundary conditions, the radius of the plastic and damage zones, the vertical and horizontal fracturing grouting pressures are deduced considering the drainage conditions and large deformation. Finally, the paper demonstrates these by engineering cases. The results show that the solution takes into account the structural parameters, compressive modulus, Poisson's ratio, internal friction angle, damage coefficient, dilatancy coefficient, form of expanding, k, yield criterion and so on. At the same time, the stress-strain distribution solution for the soil around the slurry and the grading regularity of them under the influence of the parameters are analyzed. The comparative analysis shows that the calculated value of the fracturing grouting pressure is very close to the measured value in projects, which preliminarily verifies the reliability of the theory. Therefore, the paper has considerable practical value in fracturing grouting in loess area.