The Influence Of Contact Loss Underneath Slab On Crts Ⅰ Slab Track’s Dynamic Performance

CRTS I slab track is one of the main track types on passenger dedicated lines, which requires track with high regularity and high stability. As the core technology of slab track, the emulsified asphalt cement mortar was inevitably damaged during its service life, which caused contact loss underneath slab and affected the dynamic performance of the track structure. This article is mainly about the research on the influence of contact loss underneath slab on the dynamic performance of CRTS I slab track, including the following contents and conclusions:(1) The mechanical model of CRTS I slab track was established to analyze the influence of contact loss underneath slab on the natural frequency and mode of track structure, using the finite element method. Modal analysis shows that the contact loss has a negligible impact on the natural frequency of track structure, and has a remarkable impact on the 3rd-7th mode shape of slab. Also it has a greater impact on the 8th-10th mode shape of slab.(2) Based on the modal analysis, the transient analysis is mainly about the research on the influence of contact loss underneath slab on the dynamic performance of CRTS I slab track.The transient analysis has shown that, when contact loss length is less than 0.7m, the acceleration of rail at the loading position has a significant increase. When contact loss length is 1.2m, the maximum acceleration of the rail is 2178.68 m/s2 and is as 1.66 times large as the that under the normal condition. With the increasing of contact loss length, the acceleration of slab will increase significantly. When the contact loss length is 0.7 m, the maximum acceleration of the slab is 39.78 m/s2 and is as 1.02 times large as that under the normal condition.(3)The hammering test is mainly focused on the influence of contact loss underneath slab on dynamic performance of CRTS I slab track.The time domain analysis of the hammering test has shown that when contact loss length is less than 0.7m, the acceleration of rail at the loading position has a significant increase. When contact loss length is 1.2m, the maximum acceleration of the rail is 1703.43m/s2 and is as 2.15 times large as that under the normal condition. With the increase of the contact loss length, the acceleration of the slab will increase at first and then decrease. When contact loss length is 0.7m, the maximum acceleration of the slab is 19.82 m/s2 and is as 1.8 times large as that under the normal condition.The frequency domain analysis of the hammering test has shown that with the increase of the contact loss, the acceleration of rail has a larger increase within 3000-5000 Hz within the contact loss region, and has a larger increase within 1000-3000Hz at other parts. When the contact loss length is 1.2m, the acceleration of the rail reaches the maximum. With the increase of the contact loss, the acceleration of the slab has a larger increase between 150-400Hz within the contact loss region. The peak of acceleration is at 200H. When the contact loss length is 0.7m, the acceleration of the slab reaches the maximum. With the increase of the contact loss, the acceleration of the concrete roadbed has a larger increase between 150 and 400Hz. The peak of the acceleration is at 300Hz. The contact loss underneath slab has a greater impact on the transfer function of the track structure.(4) The sinusoidal steady excitation test is mainly about the influence of contact loss underneath slab and loading frequency on the dynamic performance of CRTS I slab track.The sinusoidal steady excitation test has shown that when the loading frequency is 35 Hz, the acceleration of rail decreases with the increase of contact loss length. Under the normal condition the loading frequency is 35Hz, and the maximum acceleration of the rail is 2820.67 m/s2. With the increase of the loading frequency, the displacement of the rail at the right end is at first increase, then decrease and increase again. When the loading frequency is same, the displacement of the rail at the right end decreases with the increase of void length. Under normal conditions the loading frequency is 35Hz, and the maximum displacement of the rail is 0.4mm. With the loading frequency increasing, the acceleration of the slab increases. When the loading frequency is greater, the contact loss underneath slab has a greater impact on the acceleration of slab. Under normal conditions the loading frequency is 35Hz, the maximum acceleration of the slab is 115.93 m/s2. When the contact loss length is less than 0.7m, with the increase of the loading frequency, the displacement of the slab significantly increases. Under normal conditions the loading frequency is 35Hz, and the maximum displacement of the slab is 0.53mm.