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Structural Monitoring and Maintenance
  Volume 9, Number 1, March 2022 , pages 1-27

Stress waves transmission from railway track over geogrid reinforced ballast underlain by clay
Mohammed Y. Fattah, Mahmood R. Mahmood and Mohammed F. Aswad

    Extensive laboratory tests were conducted to investigate the effect of load amplitude, geogrid position, and number of geogrid layers, thickness of ballast layer and clay stiffness on behavior of reinforced ballast layer and induced strains in geogrid. A half full-scale railway was constructed for carrying out the tests, the model consists of two rails 800 mm in length with three wooden sleepers (900 mm × 10 mm × 10 mm). The ballast was overlying 500 mm thickness clay in two states, soft and stiff state. Laboratory tests were conducted to investigate the response of the ballast and the clay layers where the ballast was reinforced by a geogrid. Settlement in ballast and clay, soil pressure and pore water pressure induced in the clay were measured in reinforced and unreinforced ballast cases. It was concluded that the effect of frequency on the settlement ratio is almost constant after 500 cycles. This is due to that the total settlement after 500 cycles, almost reached its peak value, which means that the ballast particles become very close to each other, so the frequency is less effective for high contact particles forces. The average maximum vertical stress and pore water pressure increased with frequency.
Key Words
    ballast; clay; frequency; geogrid reinforcement; pore water pressure
Civil Engineering Department, University of Technology, Baghdad, Iraq.

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