Abstract: In order to reduce the water drainage of the studied open-pit mine, a curtain wall is proposed to cut off the river supply on the north side. With full consideration of the realities of construction site, the occluded pile curtain method is applied in an areas with a high voltage line overhead. The gravel layer thickness of the construction area is 45 m and the permeability coefficient is up to 100 m/d, with 0.033 hydraulic gradient and 5℃ groundwater temperature maintained for a long time. In order to ensure fast pile formation in deep gravel layer and low temperature dynamic water condition, a mixed impermeable material with fly ash as the main and cement and fly ash additives as the auxiliary was developed. Then, tests were carried out on the setting time, setting rate, fluidity and impermeability of the material. The mixed materials with water cement ratio of 0.7︰1.0, cement content of 40%, fly ash content of 60% and fly ash activator content of 2% shows the best performance:setting time, 102 h; setting rate, 94.6%; fluidity, 23 cm; 3 d strength, 1.06 MPa; 90 d strength, 11.65 MPa; and the permeability coefficient was as low as 8.61×10^-8 cm/s. By coring verification, the pile quality met the requirements and the water cut off effect was remarkable. The material can be used in similar projects given its anti-permeability, competitive price as well as environmental protection.