An experimental study of the effect of cement and chemical grouting on the improvement of the mechanical and hydraulic properties of alluvial formations

One of the most common methods of ground improvement is grouting. This study mainly focus on the influence of the injected urea-formaldehyde resin as an additive to cement grout forming mixed cement-chemical slurry on the improvement of mechanical and hydraulic properties of alluvial formations. For this reason, using the laboratory grout injector, the slurry from a mesh pipe located in the middle part of the specimen was injected into the specimen. The curing time, water/cement ratio (w/c) and the percentage of urea-formaldehyde resin were among of parameters have been studied. At the end, after 28 days of curing, unconfined compressive strength was performed on the specimens. Based on the results obtained, it was observed that in specimens injected by the mixed slurry with the w/c of 2, the highest amount of compressive strength was obtained when the slurry contained 10% urea formaldehyde resin. The strength of the injected specimen with the mixed slurry after 28 days of curing was increased by 150%, as compared to the case in which the cement based slurry was injected. Also, an increase in urea-formaldehyde resin in the mixed slurry led to an increase in the failure strain, the modulus of elasticity and the secant modulus. Permeability test results on the cured specimens within 28 days also indicated that injecting the cement based slurry with w/c = 1.5 and 2 resulted in 98% reduced permeability.

Alluvial formations in Iran are often encountered on many civil engineering project sites (especially subway projects), which lack sufficient strength to support the loading either during construction or throughout the service life. To improve the strength and stiffness of those less competent formations, soil stabilization with cementitious and chemical materials has been practiced. In this study, the effectiveness of grouting on improving the strength characteristics and hydraulic properties of alluvial formation at different curing ages was established with the help of experimental results.221