Study On Stability Evaluation Method Of Spur Dike Based On Life Cycle Design

Spur dikes are widely used in waterway regulation,especially in mountainous rivers.mountain rivers often have turbulent water flow due to the complicated bank slopes and river topography,and spur dikes are water-blocking structures,so the phenomenon of spur dikes being destroyed by water is common.The stability of the regulation building directly affects the effect of the regulation project.In order to avoid the potential danger and economic losses caused by the failure of the spur dike.In this paper,the new concept of life-cycle design is applied to spur dike,The core position of the performance index and economic index of the spur dike during the entire life cycle of the spur dike is defined.The stability of spur dike is studied in combination with flume experiment,so that the performance and cost of spur dike in service period are optimal.The specific research and conclusions are as follows:(1)On the basis of studying the change rule of spur dike head scour with time and combining the advantages of grey Verhulst model in "small sample,poor data" prediction,the prediction model of spur dike maximum scour depth is established.With the least measured data,the potential law of scouring process at the spur dike head is excavated,and the scouring process line of spur dike head is obtained.By comparing and analyzing the model prediction accuracy of different spur dikes and their applicability under unsteady flow conditions,a certain reference basis is provided for the prevention of spur dikes from water damage.(2)The process of maximum scour depth of spur dikes with different types of dam heads,different dam lengths and different pick angles is analyzed by moving bed scour test.By means of range analysis,the proportion of each influencing factor in the safety of spur dikes is determined.Based on the Graham evaluation method,the maximum risk velocity Umax is taken as the main hazard source,and the value-at-risk evaluation formula of spur dikes is established,which is verified by an example.The results show that the influence weight of the scour depth of groyne head on the length of spur dike is larger than that on the pick angle and type of the spur dike,and the influence weight of the structure form of spur dike on the scour depth of the groyne head is larger.the calculation results of the the value-at-risk evaluation formula of spur dikes are in good agreement with the actual situation,and the research results can provide scientific basis for the maintenance and management of spur dike project.(3)Starting from the relationship between the maximum scour depth of spur dikes and the stability of spur dikes,the stability degradation model of spur dikes is established on the basis of the four-parameter Logistic model.The economic indexes of spur dikes are analyzed and considered.An economic evaluation model of spur dike in the whole life cycle was established with the goal of minimizing the total cost in the whole life cycle,Based on the event tree model,the influence of maintenance scheme selection on the total life cycle cost of spur dikes is analyzed.The example shows that the stability degradation model of spur dikes has a good prediction effect and can be used to predict the stability of spur dikes.According to the whole life economic evaluation model of spur dikes,economy-oriented and reasonable selection of maintenance time and frequency can effectively reduce the total cost.