Design methods of coarse grained saline soil subgrade in ballastless track

A large number of saline soil area is involved in the development program of the Belt and Road Initiatives of China. The alignment of high-speed railway frequently crosses the salty desert, but it is difficult to find the favorable material of subgrade without the salt along alignment. To study the application of coarse grained saline soil in ballastless track subgrade of high-speed railway, a design method of ballastless track of coarse grained saline soil subgrade is derived with technological innovation and theoretical exploration. Different coarse particle size, salinity, subsidence coefficient and salt expansion coefficient of coarse grained saline soil was used to build the ballastless track subgrade. The base bottom layer is designed with the upper structural layer and the lower structural layer. The separation layer of subgrade base and base bed, inverted L-type protective layer, seepage and drainage ditch are used as a system, which are in charge of resistance salt and drainage salt. To ensure the ascension deformation of ballastless track subgrade to meet the design requirements, the deformation of the upper structural layer and the lower structural layer is calculated with the allowing salt expansion method. To avoid the relative slip or tensile damage of the composite geo-membrane in separation layer caused by the friction or braking force of high-speed train, the minimum sliding friction coefficient is adopted to the design. This method realizes the first application of the coarse grained saline soil in the field of ballastless track subgrade.