Experimental Investigation of Pull-Out Resistance of Grouted Soil Nails

Experimental Investigation of Pull-Out Resistance of Grouted Soil Nails—A Critical Review

Salvi, Ruchita / Juneja, Ashish

For large projects that require considerable excavation, cement grouted soil nails are the most preferred due to its cost effectiveness and simple installation techniques. The contribution of pull-out resistance to resist the tensile forces was reported to be more significant rather than the shear and bending resistance. Pull-out resistance being a significant factor for designing a soil nail slope, it is noticed that pull-out mechanism of soil nails is still not properly understood. It is observed that there is lack of explanation on the behavior at the interface of cement grouted nails and the variation of pull-out resistance due to the variation in the in-situ moisture content. This article presents a critical review of the developments related to soil nails including the recent experimental advances to correctly understand the effect of pull-out resistance and its variation with the influencing parameters. A comparative study is performed on the several experimental pull-out studies conducted in the form of large-scale pull-out box tests and interface shear tests. A detailed sequential review studies the influence of factors like in-situ moisture content, soil water characteristic curve, grout pressure, overburden pressure on the performance of grouted nails in a slope. The critical findings of the review indicate that the variation in the existing moisture content and the soil water characteristic curve strongly influence the pull-out response of the soil. Roughness of the nails and grout pressure is found to increase the pull-out resistance of the nails under the effect of low overburden pressure.