A hydraulic project in Tanzania is a reconstruction and expansion project. The original pier of the transfer section of berths 3#-4# is a gravity structure and a high-piled，reverse-beam and large-slab structure，which was built in the 1960s. The original gravity structure is retained in the reconstruction and expansion design. The cantilever high-pile cap structure，the high-pile beam plate structure，and the high-pile cap structure are used for mixed structural design to minimize the load acting on the original gravity structure and ensure the stability of the structure. The farthest part of the longitudinal beam on the land side is constructed with miscellaneous filling bottom form，which can reduce the consumption of the support system. The concrete surface layer of the high pile，reverse beam and large slab structure is reserved as the construction platform of the cast-in-place pile steel tube，which can shorten the construction period of the cast-in-place pile.