With the rapid growth of China's economy and the increase of foreign trade volume, container throughput is also increasing year by year, and its growth rate even exceeds that of container terminals. In order to meet the increasing container throughput demand of shipping companies and improve service quality, how to improve the operational efficiency of container terminals has become an important topic in the current container terminal research. The working efficiency of container terminal is mainly reflected in the loading and unloading efficiency of the bridge crane in front of the terminal and the working efficiency of the terminal yard. With the popularization of new loading and unloading technologies such as loading and unloading, double container cranes and double spreaders, the loading and unloading efficiency of bridge cranes has been obviously improved, and the key to affect the operation efficiency of container terminals is the operation efficiency. Based on this, this paper analyzes the main problems and reasons that affect the operation efficiency of container terminal yard, and how to improve the operation efficiency of container terminal yard.

Container terminal yard operations mainly include container entry and exit operations (unloading and receiving containers, loading and delivering containers, receiving containers, lifting and delivering containers) and container movement in the yard (rummaging).

1 export container loading and shipping operations

Figure (1) Export Box Operation Flowchart

2 Unloading imported containers and lifting containers.

Figure (2) Flow chart of import box operation

3. Unloading and loading operations of the transfer box

Figure (3) Operation Flowchart of Transfer Case

4. Piling and rummaging in the field

Dumping and tipping are two ways for containers to move in the yard:

Stacking transshipment refers to the operation of transferring containers from a container location in the yard to other container locations, including three processes: stacking and sending containers, collecting cards and hauling, and stacking and collecting cards.

Overturning refers to the operation of transferring other containers pressed on the container to other rows in the same position when working on the container.

Main problems affecting the operation efficiency of container terminal yard

1 The rummaging problem in the yard operation has affected the operation efficiency of the container terminal yard.

In the loading of export containers, transit containers and hoisting of import containers, there are a lot of rummaging operations, which increase the workload of yard operations and affect the efficiency of yard operations of container terminals.

Through the analysis of some container rummaging operations, it is found that some of them are caused by the unsatisfactory customs clearance of export containers, the lag of information of second-class transit containers or the hoisting time of imported containers, which is beyond the control of the terminal. However, some container rummaging operations are caused by negligence or mistakes in the arrangement plan and production organization of the wharf, which are unreasonable and should be avoided as far as possible. These rummaging operations are mainly manifested in the following aspects: 2. When arranging the entry plan of export containers, the tonnage distribution is inconsistent with the stowage requirements, which leads to the export containers rummaging about during the loading operation.

In stowage and loading operations, heavy containers are required to be at the top and light containers are required to be at the bottom. Ideally, when stacked in the yard, the heavy boxes are below and the light boxes are above. However, due to the weak controllability of the entry of export boxes, it is impossible for the wharf to stack them under heavy pressure according to the actual weight in order to improve the utilization rate of the yard. The general practice is to divide the export boxes into tons (such as 0- 10, 10- 15, 15-20, 20-25, and more than 25 tons), and then arrange the stacking scheme, and clarify the stacking principles (paying more attention to stacking and arranging according to rows)

3. When the imported box is unloaded, the new box presses the old box, which causes the imported box to turn over during the box lifting operation.

Generally speaking, imported boxes follow the principle of "first in, first out", and the ideal situation is that the newly unloaded boxes are not pressed on the original field boxes in the freight yard. However, in actual operation, due to the high utilization rate of the yard or the failure to reasonably merge and transfer the unloading area before unloading operation, there is no vacancy or empty line during unloading operation, and some tire crane drivers try to press the new unloading box on the original field box of the yard, resulting in

4. The stowage crew and the ship controller think differently about the ship operation sequence, which leads to the container being overturned during loading and unloading.

At present, the way adopted by many docks is that the ship controller arranges the operation route (arranges the operation bridge cranes and the operation times and sequence of each bridge crane), and the ship stowage officer is responsible for the ship stowage. When loading the export ship map, when a row of boxes in the yard can't be loaded in the same cabin, the shippers will assign the boxes to different cabins according to their own understanding of the loading order. However, in actual operation, if the ship's controller does not follow this idea, it will inevitably lead to the overturning of the box when it is sent. For example, there are four boxes in a row on the yard, and the ship can be equipped with two boxes according to 18 times or 22 times. If the shiploader thinks that 18 times should be done first, he will do the upper two cases 18 times and the lower two cases 22 times. However, in actual operation, if he does it 22 times first, it will inevitably lead to the need for loading first.

5. The conflict in the yard operation affects the efficiency of the container terminal yard operation.

In the process of container yard operation, operation conflicts occur from time to time, container yard operation machinery is going back and forth more and more frequently, and container trucks wait too long in the container yard, which seriously affects the operation efficiency of container yard and the quality of the company's external service.