Experimental Study of Stoneblowing Track Surfacing Technique

Ballast is known to be one of the most widely used materials for railtrack construction. Although ballast is comprised of crushed hard stones, it undergoes gradual and continual degradation under cyclic rail loading and requires constant maintenance. Due to the limitations of the commonly used ballast tamping technique for recovering railway track geometry, other technical solutions are currently being considered. Stoneblowing is an alternative technique of track level adjustment, that is defined as injection of the premeasured amount of small fresh stones with pressurized air under the sleepers, lifted to a desired level. This technique has been reported to lack most of the known disadvantages of tamping. However, postmaintenance behavior of ballast was found to be sensitive to the procedure aspects, thus further investigations in controlled laboratory conditions are required. This paper is focused on measurement and analysis of ballast settlement under cyclic loads after reinstating of a railway track with stoneblowing. Experimental results show that usage of stoneblowing leads to a predictable level of settlement, which remains constant even after a large number of loading cycles. Moreover, we propose a two-step stoneblowing technique and provide experimental evidence that this approach is more effective for reinstating the railway track than a conventional single step approach.