Mechanical property variations of base course materials caused by freezing and thawing must be considered when designing subgrades in regions with seasonal freezing and thawing. In this study, static triaxial tests were performed to investigate the properties of reconstructed base course materials with optimum water contents subjected to freeze-thaw cycles; reconstructed base course materials are extensively used for China’s high-speed railway. The material strength significantly decreased with increasing freeze-thaw cycles, particularly during the first cycle. The results show that the minimum strength was frequently achieved after the specimen had been exposed to six freeze-thaw cycles.

Coarse-grained materials are widely used in high-speed railway construction, and it is of great significance to research its compaction characteristics due to the high quality control requirements. In this regard, a field compaction experiment was conducted at a subgrade near Bazhou Station of Beijing-Xiong’an Intercity Railway. The test results of the compaction effect were presented in this study at first. The roller-integrated compaction measurements (i.e., compaction meter value, CMV) were compared with several traditional in-situ tests (i.e., plate load test, light falling weight deflectometer test, and shear wave velocity test). Then the stability of CMV was evaluated by the proposed δ criterion. The spatial uniformity of compaction was further investigated. Based on the analysis, the target value of CMV was preliminarily determined. It showed that E_vd was more variable than CMV. The results convincingly indicated that the compaction parameters increased with the increasing number of roller passes at first. A further increase in compaction effort could result in the decompaction of material when the compaction number up to a certain value. The stability analysis method proposed in this study showed its potency of quantifying the percentage of areas with acceptable compaction. The geostatistical analysis could reflect the spatial uniformity of compaction. Overall, the conducted study could provide a useful reference for geo-material compaction control in the transportation engineering.

The cyclic loading frequency (f_cyc) effects on the resilient modulus (M_r) of freezing–thawing coarse–fine mixtures geomaterials (FTCFG) have always been a research hotspot. A series of long-term cyclic triaxial tests were conducted on FTCFG having different fines content (FC) under different number of freeze–thaw cycles (N_FT) to investigate the effect of f_cyc and deviator stress amplitude (q_cyc) on the M_r of FTCFG. The freezing–thawing cyclic was found to improve the M_r of FTCFG. Additionally, M_r of FTCFG shown an obviously rate-dependent characteristics. Then three kinetic effects (rate effect, piston effect, and fatigue effect) are discussed in systemically which are related to q_cyc, f_cyc and moisture holding capacity (w_h). Finally, a rate dependent model of long-term resilient modulus was developed to predict FTCFG materials’ resilient moduli as a function of q_cyc, f_cyc and w_h. The comparisons between the calculation and experimental results reveal that the present model describes the M_r of FTCFG well.

To evaluate the service performance of the track substructure of heavy axle load (HAL) railway transportation, an inverse analysis was performed to estimate the resilient modulus values of the track substructure, based on the deflection data obtained from light falling weight deflectometer testing. Subsequently, a three-dimensional finite element model was developed to simulate the effect of the train speeds (v) and axle loads (F) on the typical dynamic responses in the railway track system. The results convincingly indicated that increasing v or F can amplify the track vibration. Finally, a critical stress ratio method was adopted to evaluate the service performance based on the numerical results. A recommended range of v and F was determined to maintain the long-term stability of the HAL railway line. The findings can provide guidance for designing the track and maintenance plans to avoid track support failures and ensure track infrastructure resiliency.

The eastern part of the Qinghai-Tibet Plateau is located in the high-altitude freeze-thaw region, where terrestrial clastic red beds formed by sedimentation since the Mesozoic are widely distributed. Recently, red-bed coarse-grained materials (CGMs) have been increasingly utilised in construction in projects across western China. However, owing to the high degree of weathering and low strength, red-bed CGMs are susceptible to particle breakage under impact loads during compaction. This process results in an increased fine particle content (FC), which exacerbates frost heave during the service period, significantly compromising engineering stability. This study investigates the particle breakage and frost heave characteristics of red-bed CGMs, focusing on the effects of water content (w), initial fine particle content (FC₀), and the number of freeze-thaw cycles (N_FT). Based on experimental data, a frost heave ratio prediction model incorporating particle breakage effects was developed. This model accounts for the influence of w, FC₀, and N_FT on the frost heave ratio of red-bed CGMs, offering a scientific foundation for evaluating the suitability of these materials as engineering fillers in high-altitude freeze-thaw regions.