Experimental Investigations on the Application of Compensation Grouting in Coarse-Grained Soils-PPT Presentation

PPT Presentation

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The study investigates how to make compensation grouting more effective in coarse-grained soils, where high permeability can cause grout to penetrate the soil or lose water through filtration rather than produce ground heave.<br /><br />Researchers developed a laboratory “soil filter press” to assess grout suitability under specific soil conditions. Tests showed that effective grout retention decreases as soil permeability increases. A lower water-to-solids ratio generally improves retention, supporting the use of grout mixtures rich in solids.<br /><br />A large-scale trial-pit experiment examined grout injection and the resulting fracture structures. About 1,440 litres of grout produced approximately 96 litres of surface heave, with a maximum of 17 mm—an efficiency of around 7%. Excavation revealed that grout formed layered, plate-like fractures, typically 0.5–1 cm thick. Later injections often followed existing fractures.<br /><br />Injection strategy strongly influenced the fracture pattern and heave. Repeated injections of small grout volumes gradually enlarged plate-like fractures near the sleeve pipes and were more effective at creating heave. Fewer injections using larger volumes tended to produce longer, narrower fractures extending farther from the pipes, which was less favorable.<br /><br />The findings suggest that compensation grouting in coarse-grained soils should use solids-rich grout with a low water-to-solids ratio, selected through soil-specific laboratory testing. In practice, numerous injection runs with small grout volumes are generally preferable to fewer injections with larger volumes.

Keywords

compensation grouting

coarse-grained soils

grout retention

soil permeability

water-to-solids ratio

soil filter press

ground heave

fracture structure

injection strategy

solids-rich grout