Efficient mitigation of edge effects in nearest-neighbor analysis

The properties of soils and other civil engineering construction materials are influenced by the microstructural arrangement of the particles. The cha racterization of the spatial arrangement and distribution of microstructura l features are therefore of importance if the mechanical properties of mate rials commonly used in civil engineering are to be better understood. Numer ous statistical methods have been developed to characterize the spatial arr angement of microstructural features. However, care must be taken in implem enting these methods using automated imaging systems to analyze finite quan tities of features so that bias due to edge effects and other factors is no t introduced. A new method for mitigating edge effects when nearest-neighbo r analysis is being performed is proposed in this paper. The method is vali dated using synthetic square and triangular patterns for which the spatial arrangement free of edge effects (unbiased) is already known. Use of the me thod to analyze a real dataset representing the peripheral packing arrangem ent of sand particles in triaxial specimens is described. The results indic ate that the new method is able to mitigate edge effects and offer substant ial savings in terms of efficiency of data collection and analysis.