Study On Design And Construction Scheme Of The Large Span Lift-lie Flap Gate Engineering

Dadongkou sluice engineering is one of four closed tidal gate engineering of Jiangxin union sea dike.There is important significance for its construction to reduce the loss caused by the typhoon storm surge in the Jiangxin union sea dike.At present,the large span lift-lie flap gate has not widely used.It has limited application for practical engineering.In the study,the large span lift-lie flap gate was applied in Dadongkou sluice engineering.Based on the geological conditions and engineering requirements of resist tide,sluicing and navigation,the design scheme and construction scheme were discussed.The main content is as followings.(1)There were four difficulties in the design scheme and construction scheme of Dadongkou sluice engineering.The first was calculating the water level and maximum discharge through sluice under different design conditions.The second was determining the total clear width of gates through comparing different sluice schemes.The third was that sluice design could meet the requirements of anti-sliding stability,seepage-proofing and settling.The fourth was selecting the suitable foundation treatment scheme and construction diversion scheme.(2)The design water level under three design conditions were obtained by using Mike11 hydrodynamic model.The selected scheme was that 2×55 m shipping gates and 8×16 m common gates,whose total clear width of gates was 238 m.In this scheme,the difference of water level between upstream and downstream was smaller,and the flow,channel narrowing and construction investment were better for this engineering.(3)There were thick silt and mucky clay in the surficial sediment at the engineering area.Through the anti-sliding stability calculation for sluice chamber foundation,the foundation stress,nonuniform coefficient and anti-sliding stability coefficient under different design conditions were obtained,but they did not meet the requirements of technical standard.Therefore,the foundation treatment was needed in this engineering.Furthermore,the cast-in-situ bored pile was used in the foundation treatment with the limitations of maximum local stress and abutment pier settlement.(4)The channel diversion was used in the construction scheme.The details were as follows.The riverway would be blocked by one time.And the open channel would be excavated at the bottomland of right side of riverway.For treating the silt and mucky clay sediment,medium-coarse sand would be riprapped,and geotechnical cloth would be paved.These treatments were to ensure the integral settlement of cofferdam.Moreover,the scour prevention would be used to improve the erosion resistibility of open channel.The large span lift-lie flap gate that constructed in the area with silt and mucky clay sediment could meet the requirements of design and construction.The design and construction schemes of Dadongkou sluice engineering in this study can be used for reference to the study of large span lift-lie flap gate.