Derailment Mechanism and Influence Factors on Number 6 Symmetric Switches

Plenty of derailments in number 6 symmetric switches occur in recent years, the derailment issue has not yet been addressed successfully. In order to discover causes and put forward reasonable measurement, the wheel/rail contact feature was analyzed based on the quasi-static theory. The coupling dynamic model of train & track was built. Taking wheel uplifted height as evaluation index, the influences of vehicle and track parameters on derailment performances were analyzed. The results show that the contact angle is only 53° when the flange touches switch rail toe, the derailment coefficient criteria is less than 0.73, which is root cause of high derailment risk.The wheel lift can be kept below 3 mm by reducing the value from 14 mm to 10 mm at the top width of 5 mm, reducing the switch angle from 1.1° to 0.9°, and reducing the stiffness of the backing plate of trackless fastener from 150 kN/mm to 50 kN/mm. It is also beneficial to prevent derailment accidents by setting a straight section with a length of not less than 3 m at the front end of the turnout, keeping a good positioning state of the axle box and keeping the side friction coefficient of the sharp rail below 0.3.