Granular soil densification using expansive resins

Area of Science:

• Geotechnical Engineering
• Material Science

Background:

• Expansive resins are used for ground improvement and soil stabilization by injecting them into soil to induce compaction.
• Current installation relies on an observational approach to grouting, involving iterative injections and in-situ testing for performance verification.
• This iterative process can be inefficient, requiring multiple injections to meet project specifications.

Purpose of the Study:

• To propose an innovative design approach for densifying coarse granular soils using expansive resins.
• To enable more accurate calculation of material quantities for ground improvement and soil stabilization projects.
• To optimize the mass of expansive resin for practical applications, promoting a sustainable and accurate design methodology.

Main Methods:

• The new design approach combines cavity expansion theory with a cubic compaction model.
• The model equates resin volumetric expansion to increased granular soil friction angle.
• Laboratory testing quantified cavity expansion, and finite element methods confirmed strain proportionality to resin expansion.

Main Results:

• Two ground improvement case studies in loose granular soils demonstrated increased soil densification between 49.5% and 51.6%.
• The new design approach showed a mean prediction difference of -0.3%, significantly better than the state-of-the-art's -19.2%.
• PLAXIS modeling indicated the new model slightly underestimates compaction with constrained surface movement and overestimates in very loose soils without heave.

Conclusions:

• The innovative design approach, verified by field case studies, offers a more accurate method for expansive resin ground improvement.
• It provides a means to optimize expansive resin mass, leading to more sustainable and precise design outcomes.
• Key factors for design include surface boundary conditions, injection depth, and in-situ density.