EFFECT OF THE CUTTING CHARACTERISTICS ON SUBGRADE UPLIFT CHARACTERISTICS IN RED-BED AREA ALONG A HIGH-SPEED RAILWAY

The smoothness of the rail surface is the essential guarantee of the normal operation of a high-speed railway(passenger dedicated line). In recent years, the continuous subgrade uplift of deep cuttings in red mudstone areas has led to significant irregularity of the track surface and seriously affected the normal operation of high-speed railways. This paper takes Neijiang North Railway Station of Chengdu-Chongqing passenger dedicated line as the research object. We have analyzed the monitoring data of subgrade surface along the railway and examined the corresponding relationship between the excavation depth of the cutting center and subgrade uplift value. Our analysis concludes that excavation unloading is an important cause of the uplift deformation of high-speed railway subgrade. We have also analyzed the cutting characteristics of the uplift section in the Chengdu-Chongqing passenger dedicated line, dividing deep cuttings into bilateral symmetrical type, bilateral asymmetric type, and unilateral type. Through uniaxial compression creep tests, we obtained sandstone and mudstone creep curves. These curves' parameters were identified using the Burgers model, and the subgrade uplift characteristics of the deep cutting in Neijiang North Railway Station were simulated using Flac3D. The simulated and measured values of uplift displacement and lateral pressure coefficient were compared and analyzed to verify the model's feasibility. Based on these results, we simulated and analyzed the characteristics of the three cutting types to obtain the bilateral symmetrical type. Then, taking the bilateral symmetrical type as an example, we studied the subgrade uplift characteristics of mudstone under different width-depth ratios and cutting slopes to determine the worst width-depth ratio and slope angle. The research results can provide a reference for the cutting design of red mudstone in a high-speed railway.