## 4 Research on the Influence of Track Structure Stiffness Change on Track Deformation
### Analysis of the Trend of the Maximum Value of Each Index Changing with the Stiffness  
Analysis of the trend of the maximum value of each index changing with the stiffness the maximum value of each index varies with stiffness, as shown in Figures 14-23, where the abscissas RB_kz, RB_ky, BB_kz, BB_ky in figures represent the vertical stiffness under rail, the lateral stiffness under rail, the vertical stiffness under block, and the lateral stiffness under block, respectively. Under the excitation of random track irregularities, the following results can be obtained by analyzing the variation tendency of each coefficient with each stiffness:  
1. When the vertical support stiffness under rail increases, the vertical acceleration of the vehicle body does not change significantly with the increase in the vertical support stiffness under rail--the lateral acceleration of the vehicle body decreases first and  
Figure 13: Variations in the deformation coefficients under different lateral stiffness under block. (**a**) Wheel-rail vertical displacement change: left-time history waveform, right-maximum, (**b**) Wheel-rail lateral displacement change: left-time history waveform, right-maximum and (**c**) Change in gauge expansion: left-time history curve, right-statistical distribution. then increases, and the vertical displacement of the rail shows an exponential downward trend. The maximum values of other coefficients show a continuous fluctuation trend with the increase in vertical support stiffness under rail. The minimum values are 140 kN/mm and 200 kN/mm. Considering the changes in the various stability coefficient of the vehicle, it is more appropriate to set the stiffness of the vertical support under the rail to 120\(\sim\)160 kN/mm. 2. When the lateral support stiffness under rail increases, it can be seen that the vertical acceleration of the vehicle body does not change significantly with the increase in the stiffness of the lateral support under rail, and the lateral acceleration of the vehicle body varies greatly with the change of the support stiffness, and there is no obvious change feature. The wheel-rail vertical force and vertical displacement of rail are almost unchanged. The wheel-rail lateral force, the derailment coefficient and the wear coefficient show a trend of first decreasing and then increasing, and the wheel load reduction rate changes in the opposite way. Judging from the wheel-rail lateral force change curve, it is more reasonable when the stiffness of the lateral support block under the rail is in the range of 160-200 kN/mm. 3. When the vertical support stiffness under block increases, the vertical acceleration of vehicle body increases with the increase in the vertical support stiffness under block, the vertical displacement of the rail shows an exponential downward trend and the lateral acceleration of the vehicle body, wheel-rail lateral force, derailment coefficient, wheel load reduction rate, and wear coefficient follows a trend of first decreasing and then increasing, indicating that maintaining the vertical stiffness under block within a certain range can increase the lateral stability of the vehicle body. The wheel-rail vertical force changes little with the stiffness. Considering the change tendency of each driving safety coefficient comprehensively, the appropriate vertical stiffness under the block is 80-100 kN/mm. 4. When the lateral support stiffness under block increases, the vertical acceleration, the wheel-rail vertical force, lateral force, derailment coefficient, wheel load reduction rate, and wear coefficient do not change significantly. and the lateral acceleration of the vehicle body changes to a certain degree of volatility, but the amplitude is small near 220 kN/mm. Therefore, it is recommended that the lateral stiffness under the block should be within the range of 160-200 kN/mm. 5. Except for the vertical displacement of the rail, all the other indicators show a continuous fluctuation trend as the stiffness of the track structure changes.