Dynamic Stress of Subgrade Bed Layers Subjected to Train Vehicles with Large Axle Loads

Abstract

The dynamic responses of subgrade bed layers are the key factors affecting the service performance of a heavy-haul railway. A 3D train-track-subgrade interaction finite element (FE) model was constructed using the ABAQUS code, where different vertical irregular track spectra were simulated by modifying the vertical node coordinates of the FE mesh of the rail. Then, the dynamic stresses in the subgrade bed layers subjected to heavy-haul trains were studied in detail. The results showed the following: (1) the transverse distribution of the dynamic stress transformed from a bimodal pattern to a unimodal pattern with increasing depth; (2) the pass of adjacent bogies of adjacent carriages can be simplified once loaded on the subgrade since the dynamic stresses are maintained around the peak value during the pass of the adjacent bogies; (3) the dynamic stress at the bottom of the subgrade bed surface layer was more sensitive to the train axle load compared with that at the subgrade surface because the dynamic stresses induced by the two rails were gradually overlaid with increasing depth; (4) the maximum dynamic stress at the subgrade bed bottom was reduced by approximately 70% compared with that at the subgrade surface; (5) the vertical track irregularities intensified the vertical excitation between the train vehicle wheels and rails, and the maximum dynamic stress at the subgrade surface under the action of the irregular heavy-haul track spectrum increased by 23% compared with the smooth rail condition; and (6) the possible maximum dynamic stress (σdm) at the subgrade surface under the action of irregular track spectra can be predicted using the triple standard deviation principle of a normally distributed random variable, i.e., σdm = μ + 3σ (where μ and σ are the expectation and standard deviation of σdm, respectively).

Analysis of Antideformation and Antivibration Effect of Different Track Beds under Subway Train Vibration

“…erefore, the irregularity of the track, including vertical irregularity, horizontal irregularity, direction irregularity, and track spacing irregularity, is an essential factor affecting the accuracy of the calculation results [33][34][35].…”

Evaluation of Critical Dynamic Stress and Accumulative Plastic Strain of an Unbound Granular Material Based on Cyclic Triaxial Tests

“…Furthermore, the ε s of saturation specimens with low confining pressures (e.g., 15 kPa in Figure 14 ) starts to increase in a large rate when the dynamic deviator stress exceeds 60 kPa. Freight trains operated in the heavy-haul railway system of China can generally impose a maximum dynamic stress greater than 60 kPa on the subgrade surface [ 17 , 57 , 79 , 80 ]. Therefore, keeping sufficient drainage capacity and preventing the subgrade approaching saturation are important in the routine maintenance of a railway.…”

Numerical Analysis of Additional Stresses in Railway Track Elements Due to Subgrade Settlement Using FEM Simulation

“…That consideration is achieved by defining the elastic parameters of the ballast layer in Table 2, such as the Poisson's ratio, Young modulus, Damping factor, and Mass density. There are many published works that have modeled the ballast layer using FEM, such as Prakoso [32], Indraratna and Nimbalkar [33], Wang and Markine [34], and Xu et al [35].…”

“…In the state without settlement, the maximum stress in the subballast layer is around 1.2 MPa, and the maximum stress in the subgrade layer is less than 0.07 MPa. Xu et al [35] concluded that the maximum stresses reached 0.08 MPa and 0.04 MPa at the surfaces of the first and second parts of the subgrade layer, respectively. By comparing the results of the maximum stress in the subgrade layer of the 2D model with the results obtained by Xu et al [35], we can conclude that the subgrade layer stresses are logical.…”

“…Xu et al [35] concluded that the maximum stresses reached 0.08 MPa and 0.04 MPa at the surfaces of the first and second parts of the subgrade layer, respectively. By comparing the results of the maximum stress in the subgrade layer of the 2D model with the results obtained by Xu et al [35], we can conclude that the subgrade layer stresses are logical. Xu et al [35] introduced the 3D track model conditions as follows: 80 km/h of wheel speed, 25 tons of axle load, 70 kg/m of rail, 50 cm of ballast thickness, a subgrade first layer of 0.6 cm, and a subgrade second layer of 1.9 m. It could be concluded that the stress values of the substructure layers are considerable; however, the recorded maximum stresses are located around the beginning and the end of the settled part.…”