Comparison of the Permeability of Potential Ballast Rocks from Northern Rio de Janeiro State under Different Fouling...

Area of Science:

• Geotechnical Engineering
• Materials Science
• Civil Engineering

Background:

• Railway ballast integrity is crucial for track safety and performance.
• Coastal proximity and sulfated groundwater pose risks to railway infrastructure.
• Rock dust contamination can significantly alter ballast properties.

Purpose of the Study:

• To analyze the impact of rock dust contamination on ballast permeability under saturated conditions.
• To evaluate the durability of different rock types subjected to sodium sulfate attack.
• To determine the suitability of local rock materials for the EF-118 railway line.

Main Methods:

• Laboratory testing of ballast samples with varying rock dust fouling rates (0-40%).
• Permeability tests using a constant head permeameter to measure hydraulic conductivity.
• Sodium sulfate attack simulation and Micro-Deval tests to assess material degradation and wear.
• Petrographic analysis and mercury intrusion porosimetry to characterize rock properties.

Main Results:

• Rock dust significantly reduced ballast permeability, with higher fouling rates leading to lower hydraulic conductivity.
• Metagranite samples (Mg1, Mg3) showed susceptibility to weathering and increased wear after sodium sulfate attack.
• Gneiss (Gn2) exhibited stable mineralogy and satisfactory hydraulic conductivity after 60 sodium sulfate cycles, indicating high durability.

Conclusions:

• Gneiss (Gn2) is a suitable material for railway ballast on the EF-118 line due to its resistance to chemical attack and good hydraulic properties.
• Metagranite (Mg1, Mg3) may be compromised by weathering and abrasion in the studied environment, potentially affecting track safety.
• Controlling rock dust contamination is essential for maintaining ballast performance and railway infrastructure longevity.