As the final batch of concrete was poured into the pile hole, all 527 bored piles of the 527-pile road-rail combined mega bridge—a controlling project of the Hefei-Chizhou Railway (hereinafter referred to as the "Hechi Railway") undertaken by China Railway Sixth Group—have been completed, pressing the "accelerate button" for the "Yangtze River Delta on Rails."

According to reports, the road-rail combined 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 Yangtze": the surface is a flow-plastic silt layer prone to diameter shrinkage and deformation, below which 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 at the top, surging in the middle, and 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.

Faced with underground challenges resembling a "blind zone," the project team introduced digital "X-ray vision" 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 the bedrock section, staged drilling and rigid guide devices were used to correct the trajectory, ensuring that 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 is about 117 kilometers long and is the core part of the Hefei-Wenzhou rapid railway corridor. The smooth completion of the pile foundations in the road-rail combined 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 reduced to less than 1 hour, which is of great significance for improving the overall efficiency of the railway network in the Yangtze River Delta region and serving the convenient travel of the people.

Source: Science and Technology Daily