At 1:18 a.m. on May 27, 2016, as the last batch of concrete was poured into the tremie pipe, the first in-water bored pile for the Jinjing Bay Bridge on the Pingtan Ring Road, constructed by China Railway Major Bridge Engineering Group Co., Ltd. Second Company, was successfully poured.

　　The first in-water pile poured was Pile No. 1 of Pier No. 4 on the right carriageway, with a diameter of 1.5 meters and a length of 44.5 meters; the designed concrete pouring volume was 94 cubic meters. It is understood that the bridge site is located in the Jinjing Bay sea area, where the geology is relatively complex and hole formation by drilling is difficult. The drilling passed through a sand fill layer, a silt layer, a silty clay layer, a strongly weathered layer, and a moderately weathered layer before entering weakly weathered granite. The flow-plastic silt layer is 21 meters thick, equivalent to the height of a seven-story building, and the area is greatly affected by natural environmental factors such as ocean waves, currents, and tides, with a maximum tidal range of more than 5 meters.

　　During drilling, the problem of mud leakage was encountered. Because the tidal range is too large and the silt layer is thick and flow-plastic, conventional methods such as following the casing and backfilling hillside soil to compact and protect the wall could not solve the mud leakage problem. After many tests by technical and construction personnel and a week of round-the-clock attempts, a series of technical parameters, including a reasonable embedded depth of the steel casing, the water head difference inside and outside the casing, and mud properties, were successfully explored. This solved difficulties such as the difficulty of mud wall protection in the flow-plastic silt layer, the easy flow of the formation when disturbed, and the effect of the large semi-diurnal tidal range on the water head difference inside and outside the casing, accumulating experience for subsequent pile foundation construction of in-water piles under the same or similar geological conditions.