Innovation and Optimization of Construction Technology for Large-Diameter Extra-Long Reverse Circulation Rotary Bored Piles and Engineering Application

In the construction of large-diameter extra-long pile foundations, technical challenges such as inadequate geological adaptability, cumbersome borehole quality control, and low reliability of pile integrity have long restricted project progress and quality. Taking the main tower pile foundation project of a newly built bridge as the research focus, this study carries out a detailed field study on the key construction technologies of φ2.0 m × 95 m reverse circulation rotary bored piles. By integrating the complex stratum characteristics of the project site—encompassing miscellaneous fill, silty clay, silty fine sand, and argillaceous sandstone—an integrated and optimized full-process construction system is developed, layered adaptive core process parameters are defined, and a targeted quality and safety control framework tailored to complex geological conditions is established. Field tests and comprehensive detection methods are employed to validate the effectiveness of the proposed technologies. The results demonstrate that the optimized construction technology effectively resolves bore-forming issues in high collapse-risk strata. All 28 engineering piles achieve 100% integrity and meet Class I pile standards. The vertical compressive bearing capacity of single piles substantially exceeds the design value. These research findings have effectively supported the successful completion of the project and offer practical technical references and engineering demonstrations for the construction of similar large-diameter extra-long pile foundations in alluvial-pluvial plain areas with complex geological conditions.