Crushed rock subgrade, as one of the roadbed-cooling methods, has been widely used in the Qinghai-Tibet Railway. Much attention has been paid on the cooling effect of crushed rock; however, the mechanical properties of crushed rock are somehow neglected. Based on the discrete element method, biaxial compression test condition for crushed rock is compiled in FISH language in PFC2D , and the natural shape of crushed rock is simulated with super particle "cluster". The effect of particle size, crushed rock strength and confining pressure level on overall mechanical properties of the crushed rock aggregate are respectively analyzed. Results show that crushed rock of large particle size plays an essential framework role, which is mainly responsible for the deformation of crushed rock aggregate. The strength of gravel has a great influence on overall mechanical properties which means that strength attenuation caused by the freeze thaw cycles cannot be ignored. The stress-strain curves can be divided into two stages including shear contraction and shear expansion at different confining pressures.
This paper puts forward the coupling model of the heat-moisture-stress field based on the governing equation of non-stationary heat transfer, moisture movement and the basic differential equations of deformation problem by displacement under axisymmetric conditions. Using a detailed calculation example for the section of the Xiang Pi Mountain in 109th National Highway, a mechanical model of the cylinder made by typical silty clay soil is simulated. Results show that in the coupling process, dynamic stress pays little contribution to the distribution of temperature field along different depths, and the amount of thawing deformation increased with dynamic loading time under the same frequency and amplitude.
Melt shrinkage, salt bulge, and corrosiveness are common problems with saline soils, which damage highway foundations and cause huge financial losses. In order to improve the saline soil subgrade, dynamic compaction(DC) and rolling compaction(RC) technology were applied on the Qarhan-Golmud Highway in Qinghai Province, China. A field experiment was conducted in which shear strength, deformation modulus, and the working mechanism of the composite foundation were analyzed after reinforcement. Both the DC and RC methods were found to be effective and helped to improve the foundation strength of saline soils, although the ultimate bearing capacity and deformation modulus of the RC method were lower than that of the DC method.
