# Rail Wear Evolution on Small-Radius Curves under Mixed Traffic Conditions, In-Field Investigations
## 4 Discussion  
All measurements were conducted at consistent locations on the outer rail over a span of five years. It is crucial to note the need for sleeper replacement after the first quarter of 2019 and rail replacement after the first quarter of 2020. Rail wear measurements were taken both before and after these replacements with the replaced sleepers and rails being identical to the original ones. Diagrams depicting lateral and vertical wear illustrate the propagation of wear post-rail replacement, along with variations in bending moments and stresses.  
The maximum allowable wear values for speeds below 100 km/h are 13 mm for lateral wear and 11 mm for vertical wear. Vertical wear values within and exceeding the limits were zero, while lateral wear values beyond the maximum limit were recorded for 75 points (18.75% of measured points). The highest wear values observed during the five-year monitoring period were 7 mm for vertical wear (curve 1) and 19 mm for lateral wear (curve 2). No maintenance activities were carried out on the rails during the investigations.  
The two curves under study differ in sleeper type: timber sleepers for curve 1 and concrete sleepers for curve 2. Railway sleepers play a crucial role in distributing loads from the wheel to the rail and, subsequently, to the ballast bed. Their bending stiffness is vital for this function, with low stiffness risking rail fatigue and high stiffness causing impact loads and vibrations. Timber sleepers offer adaptability and flexibility, while concrete sleepers, though durable, possess excessive bending stiffness, leading to strain, overloading, and changes in ballast bed grains.  
Maintenance interventions occurred over the years for both curves: sleeper replacement between 2019 I and 2019 IV (with the same type), and rail replacement between 2021 I and 2021 IV.  
Figure 18: Admissible stress evolution for the most advanced wear case, curve 1, over time.  
Contact stresses, generally compressive (except for transverse shearing stress), contribute to rail head fatigue damage. Significant wear alters the wheel-rail contact area, leading to gauge widening, especially on the outer rail. The bending moment increases significantly over the new rail situation, and lateral wear over admissible limits can reduce material capacity to support higher contact stresses.  
Both curves, experiencing mixed traffic (approximately 50% passenger trains and 50% freight trains), underwent wear measurements solely on the outer rail. Considering the distinct behavior of passenger and freight traffic, outer rail wear is attributed to passenger traffic. Despite a superelevation higher than actual traffic conditions, wear-induced speed limitations were imposed, maintaining the superelevation at initial values. High superelevation deficiencies result in increased centrifugal unbalanced force, leading to elevated pressure, lateral thrust, and wear on the outer rails.  
Effective maintenance of the rail superstructure is crucial for keeping wear within acceptable limits. Due to wear rates, speed restrictions were enforced for safety, causing delays. Proposed measures include employing high-resistance rail types in small radius curves, rail lubrication, and periodic rail geometry reconfiguration.