Quantitative　damage　identification　of　surrounding　rock　is　important　to　assess　the　current　condition　and　residual　strength　of　underground　tunnels.　In　this　work,　an　underground　tunnel　model　with　marble-like　cementitious　materials　was　first　fabricated　using　the　three-dimensional　(3D)　printing　technique　and　then　loaded　to　simulate　its　failure　mode　in　the　laboratory.　Lead　zirconate　titanate　piezoelectric　(PZT)　transducers　were　embedded　in　the　surrounding　rock　around　the　tunnel　in　the　process　of　3D　printing.　A　3D　monitoring　network　was　formed　to　locate　damage　areas　and　evaluate　damage　extent　during　loading.　Results　show　that　as　the　load　increased,　main　cracks　firstly　appeared　above　the　tunnel　roof　and　below　the　floor,　and　then　they　coalesced　into　the　tunnel　boundary.　Finally,　the　tunnel　model　was　broken　into　several　parts.　The　resonant　frequency　and　the　peak　of　the　conductance　signature　firstly　shifted　rightwards　with　loading　due　to　the　sealing　of　microcracks,　and　then　shifted　backwards　after　new　cracks　appeared.　An　overall　increase　in　the　root-mean-square　deviation　(RMSD)　calculated　from　conductance　signatures　of　all　the　PZT　transducers　was　observed　as　the　load　(damage)　increased.　Damage-dependent　equivalent　stiffness　parameters　(ESPs)　were　calculated　from　the　real　and　imaginary　signatures　of　each　PZT　at　different　damage　states.　Satisfactory　agreement　between　equivalent　and　experimental　ESP　values　was　achieved.　Also,　the　relationship　between　the　change　of　the　ESP　and　the　residual　strength　was　obtained.　The　method　paves　the　way　for　damage　identification　and　residual　strength　estimation　of　other　3D　printed　structures　in　civil　engineering.　©　2022　Institute　of　Rock　and　Soil　Mechanics,　Chinese　Academy　of　Sciences