Aiming at the derailment problem of the guard rail positions of conventional speed railway turnouts which has occurred several times in recent years,the derailment process and mechanism were studied.The rationalities of current guard rail interval and wing rail interval limits and their calculation methods were analyzed.Systematic field experimental research was conducted at 19 stations and 124 turnouts nationwide,and the optimization method of guard rail interval and wing rail interval limits was discussed.Research results show that the main reason for derailment at the guard rail position of turnout is wheel's impact on the opening section of guard rail,which leads to the loosening of guard rail bolts and the tipping and wear of guard rail,finally causing wheel to climb guard rail and derails.The distributions of guard rail interval and wing rail interval are relatively discrete during the field maintenance,with a low pass rate ranging from 68.97％to 73.83％.The existing wing rail interval limit includes a substantial safety margin,which can be appropriately relaxed to facilitate field maintenance.Compared with the double slip turnout with the same number,the probability of wheel-rail impact at the opening section of guard rail of simple turnout is slightly smaller.As the number of turnouts increases,the probability of impact at the opening section of guard rail decreases.The current guard rail interval limit setting can control the probabilities of wheel impacting the open section of straight guard rail and heel end of lateral guard rail within 12％.However,it cannot effectively prevent the wheel-rail impact at the opening section of the toe end of lateral guard rail with the probability still as high as 53.85％-75.00％.To facilitate maintenance and repair,the guard rail interval limit should be 1 365 mm,which meets the requirements of most turnouts and effectively reduces and avoids the wheel-rail impact at the opening section of the toe end of guard rail.3 tabs,14 figs,30 refs.
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