Experimental Study on Mechanical Properties of Grout-Soil Interface in Anchor System of Rammed Earthen Sites

This paper presents an experimental study on the mechanical properties of grout-soil interfaces under different grout proportions and interface forms in conservation engineering of rammed earthen sites. Calcined ginger nut (CGN) admixed with fly ash (F) and quartz sand (Q) is selected as the grouting material. Physical models of grout-soil interfaces in three groups of grouts (each group has five proportions) and different wall roughness of hole (smooth and threaded) have been made. The mechanical properties of the models including load-displacement curves and shear strength of different interfaces are obtained by an indoor push-out test system. The failure processes from interfacial shear deformation to shear dislocation are analyzed. The shear strength increases with the wall roughness of the anchor hole under the same grouting materials. Mix proportion of F (70%) exhibits the highest interfacial shear strength and mix proportion of Q (70%) gets the lowest strength. The smooth-hole wall presents the interfacial shear failure of the grout-soil, and failure in the threaded hole wall mainly shears off the soil. The three statistical models show the stress-strain relationship at the interfacial shear deformation stage. The study provides a scientific basis for the mechanical properties of the grout-soil interface and the grouting optimization of anchorage engineering in earthen sites.