Interlayer insertion and interlock will be formed when the pebbles-filled soilbags are stacked vertically and staggered

which will affect the shearing strength and failure modes of the stacked soilbags. A series of shear tests on stacked soilbags filled with pebbles was conducted to show that the interlayer insertion and interlock can strengthen the shear strength of the stacked pebbles- filled soilbags. The insertion increases as the applied normal stress increases while the interlock decreases slightly. There are two shearing failure modes of the stacked pebbles-filled soilbags during the shearing including deformation failure of filling materials (occurs first)

and followed by interlayer sliding failure. For the five layers of staggered arranged pebbles-filled soilbags

deformation of stacked soilbags will also happen before the interlayer sliding. The sliding surface of staggered arranged soilbags is ladder-like due to the interlayer insertion. Additionally

the interlayer friction resistance of the five layers of soilbags filled with pebbles is found to be related to the shape of the sliding surface.