Direct　shear　tests　were　carried　out　with　planar　interfaces　between　cemented　backfill　and　rock　to　obtain　cohesion　and　friction　angle.　Triaxial　compressive　tests　with　the　same　backfill　were　used　to　reveal　proportions　of　shear　parameters　between　interface　and　backfill.　Nonplanar　interfaces　with　different　roughness　were　shear　tested　for　further　comparison.　A　constitutive　model　for　interface　was　modified　based　on　Mohr　Coulomb　criterion,　which　could　used　to　investigate　interaction　between　backfill　and　rock　mass.　Numerical　simulated　shear　stress　strain　were　used　to　validate　the　model.