Analytic　solutions　on　twin　tunnelling　at　great　depth　in　viscoelastic　geomaterial　considering　three-dimensional　effects　of　tunnel　faces　are　presented　using　the　complex　variable　methods.　According　to　the　time　interval　between　twin　tunnel　faces,　the　proposed　solutions　can　be　divided　into　two　cases:　A)　newly　constructing　twin　tunnels;　and　B)　newly　constructing　single　tunnel　influencing　an　existing　one.　The　analytic　solutions　can　also　consider　sequential　excavations　and　the　mutual　influence　between　twin　tunnels.　The　three-dimensional　effects　of　twin　tunnel　faces　are　transformed　into　equivalent　plane-strain　problems　by　introducing　dimensionless　coefficients.　By　means　of　a　presented　general　case,　the　analytic　solutions　are　verified　via　comparisons　of　both　stresses　and　displacements　with　the　numerical　solution,　in　which　a　good　agreement　between　these　two　solutions　is　observed.　Subsequently,　a　parametric　investigation　is　performed　to　study　the　influence　of　several　parameters　concerning　twin　tunnel　geometry　and　excavation　on　stresses　and　displacements,　together　with　the　difference　between　Cases　A　and　B.　On　the　basis　of　the　results,　the　analytic　solutions　provide　quantitative　insights　into　the　essence　of　the　three-dimensional　effects　of　twin　tunnel　faces　and　would　have　certain　values　on　the　preliminary　design　stage　of　twin　tunnels.　(C)　2020　Elsevier　Inc.　All　rights　reserved.