Abstract: How to reduce the arch effect of a soil core wall effectively has become an important issue for high rock-fill dams. A common solution is to mix a certain amount of gravel into the clay soil of the core wall to increase its deformation modulus. However, the arch effect of such core walls is still significant for 300 m high dams. If more gravel is mixed, the modulus would undoubtedly be improved, but its impermeability may inevitably be weakened. This paper evaluates the feasibility of a new core wall material for high earth-rock dams–a cemented gravel-mixed soil mixed with three different soil solidifiers, examines the effects of solidifier type and content on its mechanics and durability, and demonstrates the causes of differences in its performance of different types through scanning electron microscope tests. We found the HAS type has the advantages of higher compressive and tensile strengths, larger deformation modulus and toughness, and better impermeability, frost resistance and compactness. Thus, the mixed soil of this type increases the deformation modulus of core walls without increasing the amount of gravel, helping reduce the arch effect of core walls and providing a new alternative for core wall improvement.

Key words: core wall rock-fill dam, cemented gravel-mixed soil, mechanical properties, durability, microstructure