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 different soil and grout conditions. The tests showed that grout losses increase with soil permeability. A lower water-to-solids ratio increases the effective grout fraction, supporting the use of solids-rich grouts in coarse-grained ground. The type of solid material had little influence on the effective fraction in the tests.<br /><br />A large-scale trial-pit experiment examined injection behavior and exposed the resulting fracture structures. About 1,440 litres of grout produced approximately 96 litres of surface heave, an efficiency of 7%, with maximum heave of 17 mm. Grout formed layered, plate-like fractures, typically 0.5–1 cm thick, with successive injections often following existing fractures.<br /><br />The injection strategy strongly affected fracture development and heave. Repeated injections of small grout volumes created and progressively enlarged plate-like fractures close to the sleeve pipes, providing a more effective means of generating heave. Fewer injections with larger volumes tended to create longer, narrower fractures that extended farther from the pipes and were less favorable for heave.<br /><br />For practice, the authors recommend selecting grout through soil-specific laboratory testing, using grout with a low water-to-solids ratio in coarse-grained soils, and favoring numerous small-volume injection runs over fewer large-volume injections.

Keywords

compensation grouting

coarse-grained soils

grout permeability

soil filter press

water-to-solids ratio

solids-rich grout

surface heave

fracture structures

small-volume injections

laboratory testing