Installation of 77 Offshore Deep Piles: XCMG Rotary Drilling Rig Completes Ahead of Schedule
After 100 days of construction, the Chizhou Yangtze River highway-railway Bridge, where XCMG rotary drilling rig participated, completed the final concrete injection into the conduits on July 26th and concurrently finished the construction of 77 piles for the south coast main piers ahead of schedule.
The Chizhou Yangtze River highway-railway Bridge spans a total length of 3.1 kilometers|1.9 miles, with the main bridge measuring 1768m|5,800ft. It is a three-span, three-tower, two-deck steel truss cable-stayed bridge with a main span of 812m|2,665ft, featuring characteristics such as long span, heavy load, and high speed.
For the foundation of pier No. 4 completed in this construction phase, a total of 77 drilled and cast-in-place piles were used, with a maximum pile length of 138.5m| 454ft and a maximum aperture of 2.8m|9ft. The average depth of rock penetration is about 110m|360ft, demanding high performance from the drilling equipment.
The primary rock formations at the site of pier No. 4 include siltstone, mudstone, and sandy shale. The rock layers can soften and disintegrate when immersed in water. Since the main piers of the bridge are located in the middle of the Yangtze River, the construction environment beneath the river's surface is complex. Swift water flow and significant variations in riverbed height present challenges. The soil layers to be drilled are quite hard, adding a level of difficulty to the construction of the bridge's ultra-long and ultra-deep pile foundations. Moreover, the narrow platform for operations on the river surface makes safety a top priority.
To ensure the perpendicularity of the drilling bit's penetration and accurate centering of the holes, the project team utilized a two-stage borehole expansion process with a total of 8 large-scale rotary drilling rigs in different stages, including XR800HD, XR700E, XR600E, and XR580HD. This approach not only overcame drilling difficulties and ensured the safety of drilling operations but also enhanced drilling efficiency while meeting the requirements for hole perpendicularity.
It is understood that the Chizhou Yangtze River highway-railway Bridge is a comprehensive cross-river transportation project integrating highway and railway. It spans the Yangtze River's north and south banks, connecting Tongling City and Chizhou City in Anhui Province. The upper level carries the highway, while the lower level accommodates the railway. To match the requirements of high loads for the large span and the multiple lines of road and rail, the bridge design features a three-span, three-tower, two-deck steel truss cable-stayed structure, enhancing the bridge's load-bearing capacity.
