Remedial Method for Collapsible Soil Foundation of Mosul Dam-Paper

Paper

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The study investigates grouting as a potentially more economical alternative to cement-mortar injection for reducing the risk of foundation collapse at Mosul Dam. The dam is founded on gypsum-rich soil, where water can dissolve gypsum that binds soil particles, creating voids and causing settlement or collapse.<br /><br />Laboratory tests were conducted on Iraqi gypsiferous soil containing about 20.6% gypsum. Samples were permeation-grouted with sodium silicate, silicone oil, or bentonite slurry, then assessed using oedometer, double-oedometer collapse, and direct shear tests.<br /><br />All three treatments reduced soil compressibility and collapse potential. The grouts filled voids and formed coatings or gels around soil particles, limiting water contact and gypsum dissolution. Sodium silicate and silicone oil reduced collapse more effectively than bentonite; sodium silicate was also identified as a comparatively lower-cost option. Grouting increased shear strength and cohesion, although the internal friction angle decreased slightly. Bentonite took longer to inject, consistent with its greater viscosity.<br /><br />The authors conclude that grouting may improve the performance of gypsiferous foundation soils and could be used to create a protective, relatively impermeable layer beneath the dam. However, the findings are based on laboratory-scale testing; field implementation and performance would require further investigation.

Keywords

Mosul Dam

grouting

gypsiferous soil

foundation collapse

sodium silicate

silicone oil

bentonite slurry

collapse potential

soil stabilization

gypsum dissolution