Main Bridge of Toudao Songhua River Grand Bridge Completed and Connected

At 6:45 on October 6, as the last batch of concrete for the mid-span closure segment was pumped into the formwork, the continuous girder of the Toudao Songhua River Grand Bridge on the Shenyang-Baihe High-Speed Railway, constructed by China Railway Major Bridge Engineering Group, was smoothly closed, and the main bridge achieved full connection. This marks a major breakthrough in the superstructure construction of the entire bridge and creates favorable conditions for the bridge-erecting machine to pass through the continuous girder and erect the 7-32 m simply supported box girders of the approach bridge in November. The full-bridge connection milestone will also be achieved half a year ahead of the owner's construction schedule requirements.

The Toudao Songhua River Grand Bridge is located in Fusong County, Baishan City, Jilin Province. It is a controlling, major and difficult project on the entire Shenyang-Baihe High-Speed Railway line. The bridge is 660.92 m long, with a span arrangement of 7-32 m double-track simply supported box girders plus 1-(75+136+136+75) m rigid-frame continuous girder. It is designed with 175 piles and 12 piers and abutments, and the tallest pier reaches 110 m, the highest pier of a high-speed railway in Northeast China. The two mid-span closure segments are 2 m long and were cast by symmetrical balanced pouring. Nearly 7 hours and 122 m³ of C55 shrinkage-compensating concrete were smoothly pumped, basically joining the main bridge into one continuous structure and achieving closure. Previously, they completed concrete pouring for the two side-span closure segments of Pier 10-Baifangtai and Pier 7-Pier 8 on September 22 and September 27, respectively.

The bridge crosses the Toudao Songhua River in a deep V-shaped gorge. The mountains at both ends are steep, and the bridge connects in series with tunnels under construction. There was no access road for construction. The project faced poor natural conditions, great technical difficulty and high construction standards. After mobilization, the project department successively overcame many adverse factors, including limited construction site, narrow working space, difficult material transportation, poor construction conditions and short effective construction period. They united efforts and worked solidly, carried out a series of scientific research efforts around construction production, and explored and accumulated construction experience for high-speed railway projects in high-latitude severe cold regions of Northeast China, including rotary drilled piles under complex geology, ultra-deep hand-dug piles, deep foundation pits half in water and half on shore, mass concrete pile caps, hollow thin-walled high piers, cantilever casting of large-span continuous girder segments, high and steep slope protection, and winter construction in extremely cold weather:

First, winters in Northeast China are long. The winter construction period is generally from October 15 to April 15 of the following year, leaving only half a year of effective construction period each year. They carefully studied the key-line optimization topic of factors affecting the construction period and steadily ensured progress.

Second, Pier 9 is 110 m high, the tallest pier on the entire Shenyang-Baihe High-Speed Railway and also the tallest pier of a 350 km/h ballastless-track high-speed railway in northern China. The pier shaft adopted an advanced hydraulic climbing formwork construction method, setting a new high-pier construction speed of up to 5 days per section.

Third, Pier 10 is located on a steep slope with a height difference of 50 m and a natural gradient of 45°. In light of the site terrain conditions, tower crane groups were used for construction operations, and unconventional methods such as 40 m ultra-deep hand-dug piles, 12 m sectional high-pier turnover formwork, and multi-level permanent-temporary combined protection of high and steep slopes were adopted to organize construction, keeping the schedule controllable while ensuring safety and quality.

Fourth, the 2×136 m large-span continuous girder of the high-altitude main span over the gorge adopted cantilever casting with form travelers, solving the difficulties of ultra-high pumping of C55 high-strength concrete and the strict linear control of segmental cantilever casting, and achieving precise closure of the main bridge continuous girder.

Fifth, under high-latitude severe cold weather conditions, a series of winter construction measures were taken, and winter construction was successfully carried out for 2 m diameter and 76 m deep rotary drilled piles, 5,400 m³ mass concrete pile cap pouring, and 55 m hollow thin-walled high piers.

Sixth, both ends of the bridge are connected to tunnels, and the bridge-tunnel serial connection process is complex and construction organization is difficult. During construction, the bridge-tunnel connection was successfully completed by optimizing the processes.