Abstract: A multi-index and multi-factor orthogonal experiment was carried out to explore the influence of various factors and levels on the germination, growth and root distribution of bermudagrass planted in the surface cement-modified soil of expansive soil slope of the water diversion project from Yangtze River to Huaihe River. The orthogonal experiment was designed with five factors (peat content, water retention agent content, organic fertilizer content, PAM content, and degree of compaction) and four levels. The vegetation restoration effect was comprehensively evaluated by five indexes, namely, plant germination rate, growth height, coverage, root penetration depth, and root content. Results showed that the importance of the factors affecting plant growth was organic fertilizer content, degree of compaction, water retention agent, peat content, and PAM content in descending order. Content of fertilizer and peat has a good promoting effect on plant growth and soil improvement. The higher the soil compaction degree, the worse the plant growth; to ensure better plant growth, the compaction should not exceed 86%. For the expansive soil slopes of the Y003 segment of the water diversion project from Yangtze River to the Huaihe River, the optimal improvement plan for the growth of plant (bermudagrass) is: replacing the original surface expansive soil with cement-modified soil with 9% peat, 0.05% water retention agent, 1.5% organic fertilizer, 0.05%PAM, and compaction degree at 66%. The research finding is of guiding significance for the ecological restoration of cement-modified soil in the area of diversion project from the Yangtze River-to-Huaihe River. The analysis and evaluation methods can also be used as references for the ecological restoration of cement-modified soil in other regions.

Key words: cement modified expansive soil, bermuda grass, vegetation restoration, entropy weight method, orthogonal test