With the final batch of concrete poured into the pile hole, all 527 bored piles of the Gongtie Jointly-Built Grand Bridge—a controlling project of the Hefei-Chizhou Railway (hereinafter referred to as the "Hechi Railway") constructed by China Railway Sixth Group—have been completed, pressing the "accelerator" for the "Yangtze River Delta on Rails."

According to reports, the jointly-built road-rail section of the Hechi Railway is located on the south bank of the Yangtze River and integrates national railway, regional railway, and highway functions, with a total length of 654 meters. It adopts a superimposed structure in which the lower-level railway piers "support" the upper-level highway frame. The construction area faces extreme geological challenges at the "confluence of river and river": the surface is a flow-plastic silt layer highly prone to diameter shrinkage and deformation; below lies a thick sand layer rich in confined water; and at the bottom is sandstone bedrock as hard as steel. This "sandwich biscuit"-style geology of "soft on top, surging in the middle, hard at the bottom," combined with the stringent requirements of the upper and lower structures for pile foundation verticality, makes hole-forming control like "threading a needle" at high altitude.

Facing underground challenges akin to a "blind zone," the project team introduced digital "X-ray eyes" and intelligent "stabilizers" to achieve a precise breakthrough. The project department "tailor-made" construction plans for different strata: for soft soil layers, low-speed slow drilling and high-quality mud circulation wall-protection processes were adopted to prevent hole collapse; for sand layers, mud parameter indicators were optimized and D-type drill bits were equipped to improve hole-forming efficiency; for bedrock sections, staged drilling and rigid guide devices were used to correct the trajectory, ensuring pile hole verticality deviation is controlled within 1%. At the same time, multiple quality control measures such as ultrasonic testing and double-person double-check of sediment at the hole bottom were adopted throughout the process, achieving closed-loop management of the entire process from hole formation, hole cleaning, rebar cage lowering, to concrete pouring.

It is reported that the newly built line of the Hechi Railway has a total length of about 117 kilometers and is the core part of the Hefei-Wenzhou rapid railway corridor. The smooth completion of the pile foundations in the jointly-built road-rail section has won valuable time for the subsequent construction of pile caps and pier bodies before the flood season. After the project is completed, the high-speed rail travel time from Hefei to Chizhou is expected to be compressed to within 1 hour, which is of great significance for improving the overall efficiency of the Yangtze River Delta railway network and serving the convenient travel of the people.

Source: Science and Technology Daily