English：

The riverbed landform at the No. 2 main pier of the Rongshan Yangtze River Bridge in LuzhouCity is unique, showing karst⁃like landform characteristics such as convex stone, groove, and pebblefilling, etc. There is no precedent for the construction of embedded caps under this geological condition.According to the characteristics of the project, a complete set of construction technology of casing rotarydrilling guiding hole, steel sheet pile rock embedding, sand⁃mud mixture filling and water⁃stopping isproposed,which successfully solves the problems of trench excavation and cofferdam water⁃stoppingconstruction of buried cap cofferdam under complex geological conditions of “ karst⁃like ” landformriverbed. The structural design of the buried pile cap cofferdam and the key technologies, such as guidingholes,water stopping, excavation in the construction process are introduced in detail.