Abstract　Mixed-face　ground　encountered　in　Tunnel　Boring　Machine　(TBM)　tunneling　presents　great　challenges　and　may　trigger　potential　hazards　without　warning.　A　detailed　understanding　of　such　unfavorable　conditions　is　therefore　critical　to　a　successful　bored　tunnel.　In　this　paper,　we　firstly　present　a　brief　review　of　the　definition,　classification　and　the　factors　related　to　mixed-face　conditions.　Secondly,　for　a　better　understanding　of　this　topic,　we　investigate　the　main　difficulties　and　problems　involved　in　TBM　tunnelling　under　mixed-face　ground　with　detailed　cases.　Thirdly,　from　the　viewpoint　of　rock-machine　interaction,　we　give　some　suggestions　on　the　corresponding　mitigation　measurements　from　three　categories:　(i)　selection　of　TBM　type　and　modification　of　TBM,　(ii)　condition　of　ground　and　(iii)　optimization　of　TBM　operation.　©　2015　Published　by　Elsevier　B.V.　on　behalf　of　China　University　of　Mining　&　Technology.