To address the engineering problems of road subsidence and subgrade instability in aeolian soil under traffic loads, the aeolian soil was improved with rubber particles and cement. Uniaxial compression tests and Digital speckle correlation method (DSCM) were conducted on rubber particles-cement improved soil (RP-CIS) with different mixing ratios using the WDW-100 universal testing machine. The microcrack and force chain evolution in samples were analysed using PFC2D. The results showed that: (1) The incorporation of rubber particles and cement enhanced the strength of the samples. When the rubber particles content was 1% and the cement content was 5%, the uniaxial compressive strength of the RP-CIS reached its maximum. Based on the experimental results, a power function model was established to predict the uniaxial compressive strength of RP-CIS; (2) The deformation of the samples remains stable during the compaction stage, with cracks gradually developing and penetrating, eventually entering the shear failure stage; (3) The crack and failure modes simulated by PFC2D are consistent with the DSCM test. The development of microcracks and the contact force between particles during the loading are described from a microscopic perspective. The research findings provide scientific support for subgrade soil improvement and disaster prevention in subgrade engineering.

In order to solve the problem of subgrade and foundation vibration damage induced by the railway train, a new type of rubber particle-flowable fly ash (FAR) subgrade was designed based on the principle of damping energy dissipation. The FAR material was prepared to meet the requirements of the working performance by the laboratory test, and the mechanical properties were investigated. The damping ratio characteristics of the FAR material were studied by the transient excitation method, the influence of the rubber particle content on the damping characteristics of the FAR material was analyzed and the vibration isolation mechanism of the FAR material was revealed. A 3D numerical model of track-subgrade-foundation was established by the finite element software, and the vibration isolation performance of the FAR subgrade was analyzed based on the coupled model. The results show that the rubber particles reduce the strength and dry density of the FAR subgrade. And the basic mechanical properties of the subgrade can meet the requirements of railway engineering application when the rubber particle content does not exceed 15% of the mass of solid mixture. The damping ratio of the FAR subgrade increases linearly with the increase of the rubber particle content. And the smaller the rubber particle size is, the larger the damping ratio of the FAR subgrade will be. On this basis, it is recommended to use the rubber particles with particle size of 150 mesh and particle content no more than 15%. The new subgrade is recommended for subgrade filling below the surface layer of the subgrade bed. Compared with the ordinary subgrade, the dynamic stresses of the subgrade bed bottom layer, subgrade soil and foundation soil of the FAR subgrade are reduced by 10%- 30%. In the main frequency range of the FAR subgrade vibration, the ground vibration acceleration level is generally reduced by 2-6 dB and the reduction is up to 83 dB, which verifies the good vibration isolation performance of the new FAR subgrade.

A new composite material of polyurethane-bonded rubber particle-sand mixture (PolyBRuS) is presented here. A series of cyclic triaxial tests were carried out the hysteresis curves under different confining pressures, temperatures, and freeze-thaw cycles, and then the morphological characteristics and evolution law of hysteresis curves under low-temperature conditions were analyzed. The results indicate that the dynamic strain amplitude, temperature, and number of freeze-thaw cycles have a great influence on the hysteresis curve, while the confining pressure has little influence on the hysteresis curve. While the temperature (T) is -15 degrees C and the number of freeze-thaw cycles (N) is 25, the long-axis slope K, i.e., the elastic properties and stiffness of the PolyBRuS material, decreases with increasing dynamic strain amplitude, tends to increase with higher confinement pressures. While N = 25 and the confining pressures (sigma(3)) is 25 kPa, the distance between the center point of the adjacent hysteresis curve d, i.e., fine microscopic damage of the PolyBRuS material, grows with increasing dynamic strain amplitude, rises with lower temperature. While T = -10 degrees C and sigma(3) = 25 kPa, hysteresis curve area S, i.e., energy dissipation of the PolyBRuS material, increases non-linearly in relation to the dynamic strain, and reduces with the enlarge of the number of freeze-thaw cycles, however, this reduction is negligible. Further research should focus on the quantitative analysis of the morphological characteristics and evolution law of hysteresis curves.