Shallow　twin　tunnels　are　commonly　encountered　in　urban　metro　construction.　Twin　tunnel　excavation　causes　buoyancy　effect　in　geomaterial　and　the　interaction　between　twin　tunnels　significantly　redistribute　stress　and　displacement　around　twin　tunnels.　At　the　same　time,　twin,　and　tunnelling　causes　three-dimensional　effects　around　tunnel　faces.　To　explore　the　problems,　this　paper　proposes　complex　variable　solutions　for　shallow　twin　tunnelling　in　visco-elastic　geomaterial　under　the　initial　stress　field,　considering　the　buoyancy　effect,　as　well　as　the　equivalent　three-dimensional　effect　of　tunnel　faces.　The　proposed　solutions　are　applicable　to　two　common　scenarios:　(a)　newly　constructing　twin　tunnels,　and　(b)　a　newly　constructing　single　tunnel　near　an　existing　one.　The　Schwarz　alternating　method　is　applied　to　the　proposed　solutions　to　reduce　the　half-plane　twin　tunnel　problem　into　several　connected　half-plane　single　tunnel　problems.　During　the　alternating　procedure,　a　separation　technique　is　applied　to　reduce　the　mixed　and　complicated　numeric-symbolic　calculation　into　a　simple　numeric　one　to　lower　the　threshold　of　the　algorithm　performed　on　computers　of　moderate　computation　capacity　and　considerably　save　the　required　running　time.　Additionally,　a　symmetrical　modification　method　is　applied　to　eliminate　the　displacement　singularity　at　infinity　of　shallow　twin　tunnelling　to　obtain　reasonable　displacement　in　nearby　and　far-field　geomaterial.　The　proposed　analytical　solutions　are　elaborately　verified　through　a　comparison　with　a　corresponding　numerical　solution,　which　reveals　good　agreements　between　both　solutions.　A　subsequent　parametric　investigation　is　performed　to　study　the　influence　of　twin　tunnel　geometry　(including　twin　tunnel　spacing,　depth,　relative　size,　and　relative　angle),　lateral　stress　coefficient,　preconvergence,　and　excavation　sequence　on　stress　and　displacement　in　geomaterial.　The　proposed　analytical　solutions　exhibit　high　accuracy　in　quickly　obtaining　the　stress　and　displacement　fields,　and　thus,　is　a　feasible　alternative　in　the　preliminary　design　stage　of　shallow　twin　tunnels.　©　2020　Elsevier　Inc.