In this paper the mechanical behavior of a soilbag under an increasing vertical compression is numerically investigated using a micro-polar continuum approach. Particular attention is paid to the influence of the interaction between the filling material and the bag on the evolution of the stress strain behavior of the soilbag structure. The mechanical behavior of the cohesionless granular material is described with a micro-polar hypoplastic model and for the wrapping sack an elastic-ideally plastic behavior is assumed. Two different properties of the interface between the filling material and the wrapper are investigated: a frictionless and an interlocked interface. The numerical results show that the tensile stress in the bag material uniformly increases up to limit stress for the frictionless interface while a non-uniformity of the evolution of tensile stress is obtained for the interlocked interface. The deformation patterns, i.e. zones of intense strain localization, are also influenced by the prescribed interface behavior.