# Study on Gage Widening Methods for Small-Radius Curves
## 5 Conclusions and Recommendations  
Based on the analysis of the theory of gage widening for small-radius curves in China and abroad, we examined gage widening standards in various countries and adopted dy  
Figure 18: The influence of gage widening on track maintenance and repair. (a) Current gage widening standards; (b) the original gage widening standard. namics theory to calculate the influence of gage widening on the curve passing performance. The conclusions and recommendations are provided as follows. * The existing gage widening theory can determine the minimum curve radius that needs to be widened and the gage widening value required for curves with different radii to ensure that the vehicle passes through the curves in a free-inscribed state. The theory can also determine whether multiacute locomotives can pass a small-radius curve in a normal forced manner. The theory assumes that the bogie is a rigid structure and that the wheel sets and bogies do not produce turning angles; however, it does not consider the wheel-rail creepage guiding function and the turning resistance of the car body to the bogie. Therefore, the calculation theory of gage widening is conservative, and the influence of the gage widening value on the curve passing performance and track maintenance workload cannot be quantified. * The minimum curve radius that needs to be widened is 220-350 mm; however, some countries adopt 600 m. The maximum gage widening amount range is 15-20 mm, and only few countries adopt values exceeding 30 mm. China's gage widening standards are equivalent to those commonly used abroad. * Dynamics and wear models were established to analyze the influence of the gage widening value on the curve passing performance and rail wear. The calculation results showed that when the gage widening value is increased from 0 to 10 mm, the lateral force of the curved wheel-rail with a radius less than 300 m is reduced by 16-20% and that with a radius exceeding 300 m is reduced by 10-15%. When the gage widening amount exceeds 10 mm, the wheel-rail lateral force tends to be stable, and the rail wear exhibits a similar trend. Therefore, appropriately setting the gage widening value can reduce the wheel-rail lateral force and improve curve passing performance. However, after the gage widening reaches certain values, the effects of improvement will not be apparent. * Research on the maintenance and repair of the small-radius curves of the Shijiazhuang-Taiyuan Railway showed that the replacement of the small-radius curve rail and the adjustment of the gage are primary maintenance tasks. In the rail lifecycle, the implementation of the current gage widening standard requires only one gage adjustment operation, whereas the implementation of the original gage widening standard requires doubling gage adjustment operations. Based on the simulation results and field maintenance investigation, it is better not to modify the existing gage widening standards. However, further research is still needed. The gage widening value, wheel-rail profile matching, superelevation setting, and lubrication all affect curve passing performance, and rails with small-radius curves have high wear rates and fast plastic deformation. To further analyze the influence of gage widening on rail life and track maintenance workload, we recommend establishing testing and comparison sections for long-term observation and dynamic testing. At present, we are conducting related tests on the Shuozhou-Huanghua Railway. After selecting specific test sections, we gradually adjust the value of widening small radius curves, conduct dynamic tests, observe wear development, investigate service life and maintenance workload, study the influence pattern of widening small radius curves, and check against simulation analysis. In addition, the study in this paper was mainly based on new wheels. In actual line operations, there are wheels passing through curve sections under different wear conditions.