Abstract

Al-Qa'im quarry located in Al-Qa'im which is an Iraqi town sited in about (400km) northwest Baghdad the Capital of Iraq, characterizes the main source that supplies track ballast for the maintenance of the existing railway network and construction of the new railway lines in the middle and northern parts of Iraq. Track ballast subjects a complex combination of stresses during its service life time, primarily from the repeated axial loads of the train in addition to stresses generated from the environmental conditions. The ideal evaluation of the behaviour of ballast must be tested under real field loading conditions, however such field tests are usually costly and time consuming. On the other hand, laboratory model tests simulating field loads under limited boundary conditions can provide satisfactory indication about the suitability of the material. This paper investigates the deformation characteristics of Al-Qa'im track ballast, based on repeated load model tests, simulating ballast layer under a certain selected track section. A test setup was designed and manufactured capable to applying both monotonic as well as repeated loading under different cycles and simulated tamping processes. The repeated model tests which simulate as close as possible the field conditions shed the light on the generated settlement, modulus of deformation and degradation of the ballast particles under different repeated loading levels. Statistical analysis in terms of breakage index and repeated applied load revealed satisfactory correlations that assisted understanding the overall performance of the ballast material. The results also demonstrate that 4-5 tamping are capable of controlling both the settlement and modulus of deformation of the ballast material.