Experimental study of an innovative driven and grouted soil nail (x-Nail)

This paper describes an experimental investigation of a newly developed driven and grouted soil nail (x-Nail), which combines the capabilities of a purely frictional driven nail and a compaction-grouted nail. The innovative design allows the x-Nail to be driven into the ground with a latex balloon attached that is subsequently used for compaction grouting. A grout bulb is thus formed at the driven end of the nail to improve its pull- out resistance. For compaction grouting, a special type of additive-mixed cement grout was used in this investigation because of its zero bleeding and high bond strength. A series of pullout model tests was conducted to examine the performance of the x-Nail compared to a purely frictional soil nail. It was found that more than 90% of the pullout force of the x-Nail was resisted by the expanded grout bulb and the end bearing resistance of the grout bulb increased with the increment of the injected grout volumes. The experimental results revealed that the pullout force of the x-Nail increased approximately 1800%, 1550%, 1200%, and 900% compared to the purely frictional soil nail for the injected grout volumes of about 350, 270, 220, and 170 mL, respectively. Key words: soil nail, compaction grouting, pullout force, pullout test, zero bleeding grout. Cet article decrit une etude experimentale d'un nouveau clou de sol enfonce et injecte de coulis (x-Nail), qui combine les capacites d'un clou enfonce purement par friction et d'un clou a coulis de compactage. La conception innovante permet d'enfoncer le x-Nail dans le sol a l'aide d'un ballon en latex qui est ensuite utilise pour le coulis de compactage. Un bulbe de coulis est ainsi forme a l'extremite enfoncee du clou pour ameliorer sa resistance a l'arrachement. Pour les coulis de compactage, un type special de coulis de ciment melange a des additifs a ete utilise dans cette etude en raison de son absence de ressuage et de sa grande force d'adherence. Une serie de tests d'arrachement sur modele a ete menee pour examiner les performances du x-Nail par rapport a un clou de sol purement frictionnel. Il a ete constate que plus de 90 % de la force d'arrachement du x-Nail etait resistee par le bulbe de coulis expanse et que la resistance du bulbe de coulis a l'extremite augmentait avec l'augmentation des volumes de coulis injectes. Les resultats experimentaux ont revele que la force d'arrachement du x-Nail a augmente d'environ 1800,1550,1200 et 900 % par rapport au clou de sol purement frictionnel pour les volumes de coulis injectes d'environ 350, 270, 220 et 170 mL, respectivement. [Traduit par la Redaction] Mots-cles: clou de sol, coulis de compactage, force d'arrachement, test d'arrachement, coulis sans ressuage.
Introduction Soil nailing is an effective and economical reinforcement technique in which the reinforcing slender elements (typically steel bars), called soil nails, are inserted into a soil mass by different [...]