Optimizing The Road-Rail Combined Transportation Routes-Loading And Unloading Sequences In Joint Delivery Of Military Equipment

Road-rail combined transportation is one of the important ways for our army to carry out cross-regional and long-distance joint delivery of equipment on land,and the transformation of transportation mode takes place in railway marshalling yards.It is found that due to the limitation of the loading and unloading capacity of railway marshalling yards,the equipment from different regions or different batches will often have the correlation of loading and unloading operation organization plan because of the crossing of intermodal transportation routes.This kind of correlation often leads to the interference of operation plan between the upstream marshalling yards which are responsible for loading and the downstream marshalling yards which are responsible for unloading,thus reducing the efficiency of joint delivery.Therefore,how to carry out the joint optimization of equipment transportation routes and loading and unloading operation organization plan on the basis of reasonably considering the correlation of loading and unloading activities among marshalling yards is a key concern of our military joint delivery command department at present.In order to solve this problem,this thesis mainly carries out the following work:(1)In view of the fact that loading and unloading sequences,processes and equipment selection are rarely involved in similar studies,An optimization model of military equipment joint delivery routes-loading and unloading sequences was established to minimize the total delivery time,which considers the correlation between loading and unloading sequences decisions between upstream marshalling yards and downstream marshalling yards.(2)Based on the decision logic of military equipment joint delivery,a double-layer nested heuristic algorithm is designed to solve the problem,taking routes selection decision as the upper layer and loading and unloading sequences as the lower layer.In the upper layer,simulated annealing algorithm is used to generate feasible intermodal routes scheme,and it is transmitted to the lower layer model for calculation to obtain the evaluation index value of the scheme,and then the optimal intermodal transportation routes are solved.The lower layer uses genetic algorithm to solve the optimal loading and unloading sequences of each railway marshalling yard according to the selection result of the upper layer intermodal transportation routes,and feeds the optimization result back to the upper layer.(3)In order to verify the optimization effect of the proposed method,this thesis takes the border crisis in western China as the background and considers the scale change of the joint delivery.The optimization model and algorithm of routes-loading and unloading sequences are verified,and compared with the "first-come,first-served" loading and unloading sequences mode.The results show that compared with the " first-come,first-served " model:(1)The average delivery time of the proposed model and algorithm can be reduced by about 4%,saving about 33 hours;(2)Although the joint optimization of routes-loading and unloading sequences exacerbates the phenomenon of equipment clustering and queuing in some loading and unloading nodes,the unified plan of loading and unloading operation organization among marshalling yards can release the loading and unloading capacity of high-grade marshalling yards and further improve the efficiency of joint delivery;(3)Sacrificing the efficiency of part of the upstream loading marshalling yards can not only improve the efficiency of the downstream unloading marshalling yards,but also shorten the average transportation time of equipment between each node,thus effectively shortening the total time of the delivery task.The results above verify the rationality of the model and the effectiveness of the algorithm,and its modeling and solution ideas can provide some reference for the command decision of joint delivery.