Another "world record" bridge

Eight XCMG large-tonnage rotary drilling rigs

Drilling into deep-sea sandstone

Supporting a sea-crossing passage with solid pile foundations

Recently, pile foundation construction for the main tower of the south branch main bridge of the Ganjiang Road-Rail Bridge—a key control project on the Nanchang-Jiujiang High-Speed Railway—is proceeding under tight schedule. Eight XCMG XR460D, XR550D and XR580HD super-large-tonnage rotary drilling rigs are assembled on site to handle pile foundation work for the bridge's main pier.

The south branch main bridge of the Ganjiang Road-Rail Bridge is a prestressed concrete asymmetric cable-stayed bridge. Its main tower is H-shaped, 108 meters tall, and the bridge is 510 meters long, making it the world's longest-span single-tower concrete-girder cable-stayed railway bridge designed for 350 km/h. The main pier pile foundation of the south branch main bridge consists of 23 bored cast-in-place piles with a diameter of 2.8 meters and a length of 66 meters, with the deepest piles reaching 80 meters, constructed by the tremie method.

Rotary drilling rigs must first penetrate a 15-meter overburden, then go 17 meters deep into silty clay, fine sand, gravel, and strongly weathered argillaceous sandstone, before embedding about 49 meters into weakly weathered argillaceous sandstone. Drilling and hole forming are highly difficult and carry a high risk of hole collapse, placing extremely high demands on the rotary drive and drilling tools. The rigs are also required to achieve high drilling accuracy and precise pile formation.

Racing against the dry season is another major challenge for the project. The project manager said:

"The current difficulty is to seize the dry season of the Ganjiang River to complete all pile foundation and pile cap construction, ensuring that main works are not affected by river flooding before the rainy season arrives. Construction of 18 piles must be completed before the end of December."

XCMG's XR series super-large-tonnage rotary drilling rigs have long been experts at tackling hard rock and deep piles.

The XCMG XR460D, XR550D and XR580HD all adopt a large triangular structure for greater stability when drilling hard rock, are equipped with dual rotary reducers to prevent hole deviation, and feature an intelligent control system that enables automatic adjustment and display of mast verticality, stepless adjustment of crowd force, and bottom-touch protection. Multiple rotary drive modes, including standard mode and rock-entry mode, enable staged hole forming, effectively ensuring hole wall stability and hole quality during pile foundation construction.

Currently, more than 60% of the rotary drilling rigs on site are XCMG products. XCMG rigs complete an average of one pile every six days, and the site project manager is confident about completing the schedule on time.

Taking flight as a rainbow and spanning the Ganjiang River, XCMG rotary drilling rigs will continue to contribute to bridge foundation engineering, laying solid foundations for the steel-and-concrete backbone of a strong transportation nation.