Analysis On The Cause Of Swelling Track Slab Of Double-block Ballastless Track And Improvement Measures

China is among the latecomers to the ballastless track, but the high-speed railway has realized leap-forward development. The design, construction and operation experiences of high-speed railway in China are not so sufficient that further study should be conducted on the key technical matters. During the popularization and wide application of ballastless track, its diseases are becoming increasingly obvious. The analysis on the mechanism of diseases as well as the improvement measures will become the important approach and research emphasis for the further improvement of ballastless track structure and promotion of ballastless track technologies in China.By means of field survey and numerical simulation, the transition sections on the Wuhan-Guangzhou dedicated line are considered as the research object to analyze the response of the track structure on the transition sections under the temperature load, together with the cause and influencing factors of the swelling track slab. And the relevant improvement measures are put forward. The main tasks are listed as follows.1、Based on the extensive collection and analysis of the research achievements about the design and construction of ballastless track and transition section, the train of research thoughts and methods about this paper are determined.2、On the basis of the research on the static and dynamic calculation models at home and abroad, the calculation model of the Ⅰ-type double-block ballastless on the track transition section has been established with the application of ANSYS software to analyze the response of structure layers under the temperature load. The calculation results are compared with the field test results so that the exactness of the model has been proved.3、The responses of the transition sections with different track structures under different temperature loads are analyzed. The cause of the swelling track slab has been found out and the relevant improvement measures have been put forward.The results indicate that there are two main reasons for track slab swelling.(1) The swelling free end of the track slab is caused by temperature gradient. The swelling occurs at the expansion joint on the subgrade side, about3m from the free end.(2) The swelling track slab near the anchored girder is due to the large temperature rise/drop extent. The maximum value of swelling occurs at the anchored girder and the location1-4m from the side of anchored girder-subgrade. Within the range of4-6m from the side of anchored girder-subgrade the swelling descends obviously. Beyond the range of6m, there is almost no swelling phenomenon.According to the cause of swelling mentioned above, the relevant improvement measures are raised.(1) The diseases should be dealt with in time to guarantee the operation safety.(2) The analysis about the test data should be emphasized to timely prevent the diseases from occurring.(3) The binding strength between the track slab and supporting layer within the range of possible swelling should be strengthened to decrease the longitudinal force spreading to the anchored girder. The number of anchored girder should be increased.(4) The construction procedure should be controlled strictly, including the time to loosen the fasteners, the model temperature of concrete and maintenance methods.