TY JOUR TI Influence of Upper Boundary Condition on Railway Subgrade Hydrothermal Field in Permafrost Areas KW Railway KW hydrothermal field KW permafrost KW numerical modeling KW global warming JO Bulletin of scientific research results AU Ven'shao, S.. AU Kolos, A.F. AU Petryaev, A.V. PY 2023 IS 2023 PB FSBEI HE "Emperor Alexander I St. Petersburg State Transport University"