Subgrade of High-Speed Railway on the Permafrost

Herewith the requirements to constructions of subgrade of high-speed railway on the permafrost grounds are reported. Different types of subgrades are examined, i.e. - embankments, ditch cuts and zero level, drainage and strengthening structures and also defense constructions. At the top of the subgrade a mat coats is constituted, it is made of drainage soil that does not change its state and characteristics while seasonal freeze/thaw cycles. This coat is placed 0.5 m lower than the maximum deep of thawing of ground, which is estimated by calculation. Defense constructions and embankments to be reinforced with a geonet of basalt fibers, the net to be placed every 1 m of height and across the entire width. Measures to preserve the frozen state of the following soils shall be anticipated: bedded collapsible (III type of differential settlement delta from 0.1 to 0.4) and highly collapsible (IV type with value delta > 0.4) soil of foundation and subsurface ice within 4 m below the surface as well. In these conditions, cooling apparatus (long thermic syphon). must be placed under the embankments. The mentioned method is approved to be used at the exploited railways and guarantees completely stability of the subgrade on the permafrost grounds. A mat coat to be placed in the ditch cuts and the soil within back slopes is replaced with drainage soil.