STUDY ON THE COLLAPSE MECHANISM AND EMERGENCY REHABILITATION MEASURES OF SLOPE ROAD UNDER THE INFLUENCE OF 175M WATER STORAGE OF THE THREE GORGES DAM

Under the influence of the periodic 175 m water-level fluctuation of the Three Gorges Dam,the slope of the Xiaba section of the S457 reservoir bank highway experienced deformation,leading to embankment collapse. This study investigates the stability evolution of the bank slope under water-level variations and proposes an emergency remediation support system—"micro-piles with top connecting beams+grouting+ribbed-column panels+prestressed anchor rods"—for the collapsed slope road. The implementation of the support system effectively stabilized the subsided roadbed. The results indicate that: (1)During the initial stage of rapid water-level drawdown,pore-water pressure response in the slope lags behind external water-level changes,generating downward seepage forces at the slope toe. This causes the stability factor to abruptly decrease to its minimum of 0.99,representing the most critical phase. Remediation may be considered if failure has not yet occurred. (2)For roadbed treatment,the"micro-piles+grouting+steel truss" method forms a three-dimensional protective network: micro-piles provide vertical anchorage,steel trusses deliver lateral constraint,and grouting achieves comprehensive reinforcement. This system enhances the shear strength and bearing capacity of subgrade soil while transferring loads to underlying stable bedrock,thereby consolidating the roadbed and improving slope stability. (3)For the external embankment,the treatment method of"ribbed-column panels+prestressed anchor rods" was adopted. The rigid support of ribbed-column panels and the active reinforcement of prestressed anchor rods work synergistically,effectively improving the anti-overturning performance of the micro-pile-reinforced geomaterials. After treatment,the stability factor at the most critical moment increased to 1.18. Field verification confirms the system's structural integrity,rapid constructability,and cost-effectiveness. Over five years of service,it has repeatedly withstood water-level fluctuations,offering a valuable reference for analogous coastal slope collapse remediation projects.