The low pull-out resistance and the limited understanding of how the sleeper materials affect the screw pull-out behaviour is one of the key reasons for the lack of confidence in the wide adoption of available composite railway sleepers. In this study, the pull-out strength and the failure analysis through hole microstructure of different sleeper technologies including timber, synthetic composite, recycled plastic and Particulate Filled Resin sleepers were investigated. Also, the effect of material properties on the screw pull-out strength and failure behaviour was determined. The results showed a statistically significant difference in pull-out strength among different sleeper technologies and the paired samples test revealed a high correlation between the pull-out strength and the shear strength of the materials. A simplified prediction model was developed to predict the pull-out resistance for railway sleepers based on shear strength of the composite sleepers. This proposed equation shows a better agreement with the experimental results than an existing theoretical equation regardless of different pull-out behaviour.

低拉出阻力和对轨枕材料如何影响螺杆拉出行为的了解有限是对广泛采用可用复合铁路枕木缺乏信心的关键原因之一。在这项研究中，研究了不同轨枕技术（包括木材、合成复合材料、再生塑料和颗粒填充树脂轨枕）的拉拔强度和通孔微观结构失效分析。此外，还确定了材料特性对螺钉拔出强度和失效行为的影响。结果表明，不同轨枕技术之间的抗拔强度存在统计学显着差异，配对样本试验表明，抗拔强度与材料的剪切强度之间存在高度相关性。开发了一种简化的预测模型，以基于复合枕木的剪切强度预测铁路枕木的抗拔力。与现有的理论方程相比，无论不同的拉出行为如何，该提议的方程都显示出与实验结果更好的一致性。