The　ground　motion　around　underground　tunnels　can　vary　significantly　from　the　free-field　site　response　due　to　wave　scattering,　thus　influencing　the　seismic　demand　for　the　design　of　aboveground　structures　in　the　vicinity.　This　paper　numerically　investigates　the　effects　of　a　rectangular　tunnel　on　the　ground　motion　of　a　saturated　poroelastic　half-space　for　obliquely　incident　seismic　waves.　The　results　show　that　the　ground　surface　accelerations　can　be　significantly　modified　by　the　rectangular　tunnel,　while　the　modification　is　a　function　of　the　soil　property.　It　is　shown　that　the　differences　in　the　ground　motion　amplification　between　the　saturate　and　dry　poroelastic　half-spaces　are　noticeable,　both　in　terms　of　the　magnitude　and　period　contents　of　the　ground　surface　accelerations,　and　moreover,　the　saturation　degree　is　a　critical　factor　that　can　influence　the　ground　motion　amplification　to　a　great　degree.　©　The　Author(s),　under　exclusive　license　to　Springer　Nature　Switzerland　AG　2022.