For　deep-buried　shield　tunnels　in　sand,　it　is　difficult　to　determine　the　loosening　earth　pressure　in　front　of　tunnel　face　due　to　the　significant　soil　arching　effect　during　excavation.　Considering　the　soil　arching　effect　and　the　correlation　between　the　relative　displacement　of　soil　and　the　arching　deformation　patterns,　this　paper　proposed　a　new　analytical　model　of　loosening　earth　pressure　in　front　of　tunnel　face.　This　soil　arching　effect　refers　to　the　load　transfer　of　parabolic　soil　arch,　the　height　of　shear　bands　and　the　lateral　stress　ratio　on　both　sides　of　rectangular　arch.　Formulas　for　calculating　the　three-dimensional　loosening　earth　pressure　were　deduced.　Then　the　reliability　of　this　model　was　verified　through　comparing　the　results　from　the　proposed　model　and　the　three-dimensional　trapdoor　experiments.　Subsequently,　this　model　of　loosening　earth　pressure　was　introduced　into　a　five-truncated　cones　model　to　compute　the　limit　support　pressure　on　tunnel　face.　Finally,　comparisons　of　the　proposed　model　and　classical　models　as　well　as　typical　centrifuge　model　tests　were　conducted.　Comparative　analysis　shows　the　proposed　model　of　loosening　earth　pressure　excels　the　classical　models,　and　the　failure　zone　predicted　by　the　proposed　model　is　in　good　agreement　with　that　obtained　from　centrifuge　model　test.