Stabilisation of the Track’s Subgrade Foundation by Injection in the Case of Degradation of Permafrost Soils

The location of the railway infrastructure on permafrost increases risks of emergence of defects and deformation of the subgrade. In Russia permafrost occupies approximately 65 % of the country’s area. Consequently, defectiveness of subgrade in the Eastern part of railway network of Russia exceeds the network’s average. The objective of the study was the increase in the efficiency of stabilisation of track subgrade’s foundation with injection method under the conditions of degradation of permafrost soils. An improved algorithm for designing pressure injection of cement-soil grout, implementing an integrated approach, is proposed for railway subgrade operated under conditions of degradation of permafrost soils and formation of soft soils in foundations. A laboratory experiment was set up and carried out to determine the amount of heat released by injected grout of various composition due to the exothermic reaction of hardening of cement, that allowed determining a linear dependence of the specific heat release of injection grout on the cement content. A new calculation scheme with an equivalent layer of grout in the stabilisation area has been proposed to predict the amount of thawing of permafrost foundation soils when injecting materials with a cement binder, and an analytical solution to the problem under consideration has been proposed for preliminary calculations.