On April 12, 2016, trial pile tests were completed on-site for large-diameter high-strength prestressed concrete pipe piles (PHC piles) used in the soft soil foundation area of bridges in the Jingyue Section of the Menghua Railway. All data met the design requirements, and construction can now be promoted.
Large-diameter PHC piles have the characteristics of high strength, reliable quality, material savings, and high bearing capacity. They are widely used in the port industry but rarely in the railway industry. In recent years, the China Railway Corporation has been vigorously promoting the use of PHC pile foundations. Especially in heavy-haul railway bridges, the use of large-diameter PHC piles offers good economy and safety. At the same time, installing inclined piles in soft soil areas can better meet the longitudinal stiffness requirements of piers.
The Jingyue Section of the Menghua Railway crosses the Jianghan Plain and the Dongting Lake Plain, where soft soil foundations are widely distributed. To ensure construction safety and save project investment, the bridge discipline adopted φ1.0m diameter PHC piles in some bridge pile foundations during the construction drawing stage, involving 109 bridge piers, with a total pile length of 41,125 m. According to estimates, this saves nearly 40 million yuan in investment compared to conventional bored piles, and saves about 40% of foundation investment per bridge pier. Since the application of large-diameter PHC piles in the railway industry is still in its initial stage of development, and considering the impact of the Menghua Railway's unit price bidding system, there are certain difficulties in implementing large-diameter PHC piles. To this end, the China Railway Engineering Design and Consulting Group Bridge Institute arranged technical personnel to conduct research and learn from the East China region and the port industry, gaining an in-depth understanding of the details of PHC pile manufacturing, transportation, and construction. After multiple communications and reports with the construction unit, they gained the trust and support of the construction unit.
With the cooperation of the construction unit, trial pile tests have been carried out successively since the beginning of the year. During the testing process, the on-site bridge discipline team participated throughout, closely followed the test progress, grasped the test data, and promptly solved the difficulties encountered during the driving construction. Ultimately, the test achieved the expected design goals. The success of this trial pile test has laid a solid foundation for subsequent promotion and construction on site, and has accumulated valuable experience for promoting the use of large-diameter PHC piles in Central China and railway bridges.