Ice Jam Risk Assessment Of Water Transfer Project Design Scheme

The middle route of South-to-North water diversion project is an important water transfer project to solve the uneven distribution of water resources in China.In winter,ice jams occur in the northern canal during the water delivery process.At present,the risk assessment index system and methods for water transfer projects have problems with single perspective and failure to consider the series response of the canal system.Therefore,it is necessary to study the series response characteristics of the canal system and proposes a risk assessment method that is conducive to the prevention and control of ice jam in the whole life cycle of the water transfer.This research takes single canal as the assessment unit,and the comprehensive risk degree of the ice jam includes the basic risk degree and the secondary risk degree.Firstly,combining the basic design parameters of canals with ice jam formation mechanism,the risk factor hierarchy system is identified,and then the risk factor weights are determined using the AHP and the entropy weight method so that a basic risk assessment method is proposed.Secondly,with the analysis of hydraulic response consequences of the ice jam in the long-distance water transfer project,standards for the secondary risk and severity of consequences are established,and then the calculation method of the secondary risk degree is put forward,which helps to confirm the comprehensive risk degree and form the comprehensive risk level so as to obtain the ice jam assessment method.Finally,taking the middle route of the South-to-North diversion project as an example to carry out the method application,this thesis puts forward some suggestions on the prevention and control of ice jam risk from the perspective of the whole life cycle of the project.The results prove that the basic risk factors system includes three first-level factors of ice production causes,special buildings and basic design parameters,which are divided into 17 three-level factors;according to the weights,special buildings are the most important first-level risk factors,while temperature zone,length of canal,number and location of aqueducts and number and location of inverted siphons,bottom slope change are the main risk factors for ice jam risk;under the feedback of PI controller,the ice jam event only has a hydraulic response effect on the upstream channel,which has the potential to induce secondary ice jam hazards;Jingshi section consists 13 canals,of which 6 canals have a comprehensive risk degree of IV,including 3 ponds with a basic risk degree of III;in order to promote ice jam risk prevention and control from the perspective of the entire life cycle of water transfer project construction,risk prevention and control measures should be taken in advance during engineering design.