Abstract
Freeze-thaw damage is a typical distress incurred in road and railway engineering in cold regions. Concrete waterproofing layer is commonly used in high-speed railway tracks to prevent the penetration of surface water, however, it cracks easily under thermal stress, especially in cold regions. Recently solutions have been proposed to increase the waterproofing layer’s cracking resistance by using asphalt layers. Nonetheless, the use of emulsified asphalt as well as dense-graded asphalt mixture were not effective enough. To improve the effectiveness, in this study, mastic asphalt was designed for application as the waterproofing layer on the subgrade surface of high-speed railway tracks in cold regions. The overall performance of mastic asphalt was preliminarily evaluated by laboratory tests, then a 200-m test section was constructed for field validation in northeastern China as part of a new high-speed railway line, and water content sensors were placed inside the subgrade to monitor the performance of the mastic asphalt waterproofing layer (MAWL). The subsequent field investigation and monitoring data during the two years operation showed that MAWL dramatically outperformed the conventional concrete waterproofing layer in terms of waterproof performance. Plenty of serious cracks were found in the conventional concrete waterproofing layer, but only a limited number of local cracks were observed in MAWL. As a result, MAWL keeps the water content of subgrade at a stable level. In addition, MAWL showed relatively high stability during the two years investigation period, and no obvious deterioration was observed in the test section.
Highlights
Freeze-thaw damage of subgrade is a typical cause of deterioration of road and railway structures in cold regions
In the high-speed railway track system, the waterproofing layer performs the role of preventing surface water from penetrating into the subgrade
Mastic asphalt mixture used for the waterproofing layer is required to have adequate cracking resistance and high-temperature stability, as well as impermeability
Summary
Freeze-thaw damage of subgrade is a typical cause of deterioration of road and railway structures in cold regions. In 2005, a dense-graded asphalt mixture was used in the Beijing high-speed railway test track as the waterproofing layer, but plenty of cracks were found after several years of operation, and insufficient compaction and poor cracking resistance were reported to be the main reasons. Based on the experiences mentioned above, the use of asphalt layer in railway tracks helps to reduce train-induced vibration, improve waterproof performance, and increase stability of the subgrade, due to poor workability and insufficient cracking resistance, the asphalt mixture used in sub-ballast layer cannot meet the requirements of the waterproofing layer in the slab track. The mastic asphalt mixture was designed and evaluated in the laboratory, a 200-m test section was constructed as part of a real high-speed railway line in northeastern China, and field investigation results and monitoring data over the two years of operation were analyzed and compared with conventional concrete waterproofing layers
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have