The container yard is the key element of any modern container terminal. The huge amount of boxes dwelling on the operational areas of the terminals could occupy a lot of space, since one-time storage capacity of the container mega terminal handling over one million TEUs annually is something around 20 000 TEUs. The ecological pressure imposed on modern container terminal does not permit to allocate for this storage large land areas, thus forcing the box stacks grow high. The selection of the individual boxes becomes a complex and time-consuming procedure, demanding a lot of technological resources and deteriorating the service quality. The predicted combinatorial growth of redundant moves needed to clear the access to the individual container is aggravated by the well-known and widely discussed ‘sinking effect’, when containers arrived earlier are gradually covered by the ones arriving afterwards. While the random selection could be adequately assessed by combinatorial methods, the ‘sinking effect’ allows neither intuitive consideration, nor any traditional mathematical means. The only practical way to treat this problem today is in simulation, but the simulation itself causes yet another problem: the problem of model adequacy. This study deals with one possible approach to the problem designated to prove its validity and adequacy, without which the simulation has naught gnoseological value.
The box selectivity in operational stack of container terminal is a quite common and long studied question. The pure random choice is governed by the theory of probability offering some combinatorial estimations. The introduction of operational rules like import/export separation, storage by shipping lines, sorting by rail or truck transportation etc., as well as the most notorious ‘sinking’ effect, i.e. covering of boxes arrived earlier by next cargo parties – all these blur the clear algebraiс picture and lead to appearance of many heuristic outlooks of the problem. A new impetus to this problem in last decades was given by the rapid development of IT, AI and simulation techniques. There are quite many examples of the models described in the scientific publication reflecting many real and arbitrary terminals, which embed very advanced and complicated mechanisms reflecting selected features and strategies. Unfortunately, these models usually are created ad hoc, with some pragmatic objectives and under the demand of closest possible proximity to the simulating objects. There are much less models designated to pure scientific study of the deep inner mechanisms responsible for the primal behavior of the operating container stack, enabling to introduce step by step new rules and restrictions, providing regular proving of every next stage’s adequacy and easy to use. This paper describes one attempt of this kind to create a new theoretical tool to put into the regular toolkit of the container terminal designer. The study starts with mathematical (combinatorial) considerations, proceeds with some restrictions caused by physical and technological characteristics, and ends up with the simulation model, which adequacy is confirmed by practical results.
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