Sandy　cobble　strata　is　one　of　the　most　commonly　encountered　engineering　geological　body.　A　further　research　into　the　stability　of　ground　and　underground　structure　demands　for　precise　modeling　of　actual　formation.　In　this　paper,　a　meso-scale　numerical　method　for　modelling　sandy　cobble　strata　is　presented,　which　considers　rock　blocks　and　soil　matrix　as　separate　constituents.　In　the　approach,　the　particle　size　distribution　and　spatial　distribution　of　rock　blocks　are　two　crucial　points.　For　the　first　point,　i.e.　the　particle　size　distribution　of　rocks,　the　fractal　scaling　theory　is　included　in　particle　size　distribution　description　and　design.　In　the　log-log　plots,　60　sets　of　particle　size　distributions　of　sandy　cobble　soil　in　Beijing　are　examined　for　fractal　behavior.　For　the　second　point,　i.e.　the　spatial　distribution　of　rocks,　the　Monte-Carlo　principle　is　used　to　generate　random　spatial　distribution　of　rocks　in　soil　matrix,　while　the　rock　shape　is　assumed　to　be　circular　in　two　dimension,　or　sphere　in　three　dimension.　Based　on　the　compassion　of　rock　volume　content　between　the　numerical　model　and　theoretical　calculation　value,　it　is　validated　that　the　meso-scale　method　could　basically　be　used　to　establish　the　meso　model　of　sandy　cobble　strata.　Then,　the　present　sandy　cobble　strata　model　is　extended　to　investigate　tunnel　excavation　in　such　a　formation.　Based　on　the　simulation　results,　the　deformation　characteristics　on　transverse　section　and　longitudinal　profile　are　explored　respectively,　and　their　variations　with　fractal　dimension　or　the　maximum　rock　size　are　discussed　subsequently.