Modelling of compaction grouting based on the unified strength theory considering the grout permeation effects

Conventional compaction-grouting models often neglect the intermediate principal stress and grout-induced seepage forces, limiting their ability to represent the actual soil response. This study develops a theoretical model based on steady-state seepage theory, cavity expansion theory, and the unified strength criterion. The model is validated against existing theoretical solutions and engineering measurements, and an expression for the ultimate grouting pressure is derived. Parametric analyses are conducted to examine grout-bulb expansion, plastic-zone development, and soil stress distribution. Results show that radial and circumferential stresses in the plastic zone increase with soil cohesion and internal friction angle. The ultimate grouting pressure increases with cohesion, internal friction angle, and Poisson’s ratio, but decreases with elastic modulus. The predicted grouting pressure agrees well with field measurements, confirming the reliability of the proposed method and its applicability to compaction-grouting design in geotechnical engineering.