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A numerical model based on cellular automaton algorithm is developed to simulate dendrite growth at the edge of weld molten pool and the solute diffusion during grain growing process in weld solidification is analysed too. By means of two-dimensional square cells and von Neumann neighbourhood, the growing morphologies of the columnar dendritic grains with different cooling rates and different numbers of seeds are simulated. The growth of secondary dendrite arms, tertiary dendrite arms and their competitive growth are also presented. The results illustrate that the final primary dendrite spacing depends on the number of seeds that initially generated. With increasing cooling rate, the growing speed is increasing obviously. It is also indicated that competitive growth exists between different dendrite arms. The tendency of competitive growth in high cooling rate conditions is weaker than the one in relatively small cooling rate conditions.

Earthen sites are valuable cultural heritage sites in arid regions of NW China, where a series of serious deteriorations have developed. Scaling off is a typical type of deterioration that greatly threatens the long-term preservation of earthen sites. To date, there are insufficient studies on the formation mechanisms and influence factors of scaling off, leading to a lack of a theoretical foundation for further consolidation research. Therefore, establishing a scientific evaluation system to explore the formation mechanisms of scaling off and assess its degree of development has become a very significant topic for earthen site conservation. In this study, we selected 18 earthen sites to survey scaling off in the field, and data from geotechnical tests and meteorology were then collected to fit the characteristic values to determine the influencing factors. Finally, fuzzy analytic hierarchy process (Fuzzy-AHP) was applied to build a system to evaluate scaling off. The mechanisms of scaling off formation were explained by comparing and analyzing the porosity, shrinkage limit, particle size distribution of rammed earth and environmental factors combined with soluble salt contents in rammed earth. This research reveals the formation mechanisms and influencing factors of scaling off from a new perspective, which will lay a beneficial foundation for further consolidation research.

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