Abstract: The construction of highway has given rise to a large number of engineering accumulation which occupies valuable land resources and also exacerbates soil loss. The aim of this study is to investigate the impact of rainfall intensity on soil nutrients and soil particle composition in engineering accumulations with varying gravel contents in the Karst area of Guangxi Province. Our experimental materials consist of pure soil deposits (0% gravel content), soil-rock mixtures with higher soil content (30% gravel content), and soil-rock mixtures with higher gravel content (70% gravel content). We conducted indoor rainfall simulations with different intensities (30, 60, 120, 150, 180 mm·h^-1), and measured the variations of soil organic matter, total nitrogen, total phosphorus, and soil particle composition in the engineering accumulations. Results indicate that the nutrient contents of pure soil deposits were significantly higher than those of engineering accumulations with soil-rock mixtures before and after rainfall (P<0.01). After rainfall, the contents of total phosphorus, total nitrogen, and organic matter in the surface of accumulation slope decreased by 9.37%-54.76%,15.24%-38.33%, and 14.63%-38.66%, respectively. However, there were no significant differences in soil nutrient contents among different rainfall intensities (P>0.05). Additionally, after rainfall, the clay content and sand content decreased while the silt content increased in pure soil accumulations; while clay content decreased and sand content increased in engineering accumulations with soil-rock mixtures. Furthermore, a highly significant positive correlation was observed between soil nutrients and clay content (P<0.01). The research findings provide a scientific basis for soil and water conservation as well as soil resource management in engineering accumulations resulted from highway construction in Guangxi.

Key words: engineering accumulation, rainfall intensity, soil nutrients, soil particle, highway