Pullout Testing of Soil Nails in Gneissic Residual Soil
A.C.N.B. Arêdes, E.A.G. Marques, A.H.C. Oliveira
Soils and Rocks, São Paulo, 43(1): 85-96, January-March, 2020 | PDF
Soil nailing has proved to be an efficient and cost-effective stabilization technique, consisting in installing passive reinforcement in the soil that provides the material with tensile and shear strengths. The fundamental parameter in analyzing the mechanical behavior of this type of structure is the frictional resistance of the soil-nail interface, denominated qs. This paper presents the results of pullout tests performed on a slope located on the campus of the Federal University of Viçosa, in Viçosa-MG, Brazil. Drilling boreholes enabled the identification of four different types of soil with predominant composition of fine sand and silt, all characterized as a gneissic residual soil. Different lengths and methodologies were studied in the pullout tests with the aim of assessing the impact these factors have on shear strength. The values of qs obtained in the tests were similar to the ones reported by other authors. Even when running tests with low pressures, the results showed that the first grouting reinjection stage was able to provide a significant gain in the pullout resistance of the nails. Another point of observation was that, even though there are reasonable estimated values of qs in the literature, the conduction of pullout tests is essential for the confirmation of the values to be used in each situation.
Submitted on April 10, 2019; Final Acceptance on October 1, 2019; Discussion open until August 31, 2020.