Field Experimental Study on Compaction Performance of Impervious Soil Material in High Altitude Borrow of an Ultra-high Earth-rockfill Dam

An impervious soil material borrow of an ultra-high earth rock dam is located at an altitude of 3500 m. In-site compaction test of soil was carried out at this elevation. The tests include the selection of compaction parameters, the influence of variable moisture content on soil compaction characteristics, and the comparative study of compaction effects of different compaction methods. The experimental research shows that when the paving thickness of soil is 35 cm, the greatest degree of compaction is acquired. Considering the design index of soil compaction and cost, the paving thickness is determined as 30～35 cm and rolling times is 10. It is found that when the thickness of soil material is thin, the more rolling times, the greater the disturbance and the worse the compaction degree. Combined with the climatic conditions of the soil borrow, it is found that the loss of soil moisture content is 1.2% in the whole process from soil loading to compaction. By changing the moisture content of soil, the influence of moisture content on the compaction effect is explored, and the range of compactable moisture content of soil in the project is determined. The comparative experimental study of different compaction methods shows that the compaction degree obtained by vibratory flat roller is higher than that by vibratory bump roller under different paving thickness and rolling times.