Stability Analysis And Application Research Of Spur Dike Based On Reliability Theory

Spur dike,as a waterway regulation building,plays a very important role in waterway regulation engineering.Due to the channel environment and loose structure of spur dike,it can’t resist the scouring of flood,resulting in frequent water damage.In order to effectively reduce the damage of spur dike caused by flood,the stability of spur dike should be comprehensively analyzed in design.Based on the field investigation of"7.11 flood accident"in Jialing River waterway,it has been analyzed the characteristics and causes of spur dike water damage,and the stability of spur dike was further analyzed according to the principle of reliability.（1）Based on the analysis of more than ten spur dike damages in 8 reservoir areas including Cangxi and Xiaolongmen in the"7.11 flood accident"of Jialing River,the main cause of spur dike damages is that the large flood occurred in Jialing River,and the stability of newly built spur dike itself was not enough to resist the impact of flood.The impact of flood should be fully recognized in the design,and the corresponding standard flood should be considered and the flow should be taken as the leading role in corresponding stability calculation and analysis.（2）Based on the analysis of the water damage characteristics of spur dike and the corresponding restoration conditions,the failure modes of spur dike can be classified as spur sliding failure,start-up failure of armor block,scouring failure at dam toe,scouring pit at dam head and combined failure.（3）According to the stability calculation of 8 spur dikes in Jialing River waterway regulation project and the analysis of reduction condition series,it has been known that the design water level of spur dikes in design condition combination should select the lowest navigable water level,regulation water level,highest navigable water level and design flood level（once in 20 years and once in 50 years）;the control water level of dam sliding failure is the highest navigable water level,and the stability of design flood level should be checked Qualitative analysis shows that the control water level for the start-up failure of revetment block and the scouring failure of dam head is the regulation water level,and the corresponding water level causing larger flow velocity is checked.（4）Based on the reliability theory,according to the design principle of hydraulic structures in waterway regulation project,the design expression of spur dike stability expressed by partial coefficient is given,and the corresponding calculation conditions are given.Considering the working characteristics of spur dike in waterway regulation project and referring to the practical experience of port engineering and related hydraulic structures,the target reliability index β of spur dike stability is proposed to be 2.7 Through the analysis and comparison of the actual project and the trial design calculation,the partial coefficient γ_P of flow force,the partial coefficient γ_PT of flow thrust,the partial coefficientγ_PB of wave force and the partial coefficient γ_R of self weight are recommended to be 1.45,1.4,1.3 and 1.0 respectively.（5）The stability analysis and design method of spur dike,the target reliability index and the corresponding partial coefficient values proposed in this paper can provide an important reference for the design of spur dike.