Study on the Influence of Sustained Axial Compression and Tension on the Permeability Properties of Panel Concrete

The anti-seepage performance of concrete directly affects the anti-seepage effect and durability of the concrete face slab of the rockfill dam. Since the panel concrete is often in a complex stress state in practical engineering, its permeability coefficient will be significantly affected by the stress state. In this paper, the fixture is designed to apply different levels of axial compression and axial tensile load to concrete specimens, and the air-void structure, water absorption, and permeability coefficient are measured under sustained load. The results show that with the increase in axial compressive load, the air-void spacing, capillary water absorption and permeability coefficient decrease first and then increase, and the critical stress threshold is 0.38 fc. For the specimen with a water-cement ratio of 0.35, the permeability coefficient decreases by 45.1% and then increases by 802.4%. However, when the axial compressive load exceeds a certain threshold, the internal structure is damaged, and the permeability increases again. With the increase in axial tensile load, the air-void spacing, capillary water absorption, and permeability coefficient continue to increase, indicating that axial tensile stress will aggravate the expansion of micro-cracks in concrete and significantly increase the permeability coefficient. For the specimen with a water-cement ratio of 0.35, the permeability coefficient increases by 197.9% and then increases by 734.3% with the increase in tensile stress. The concrete with a water-cement ratio of 0.5 is more sensitive to the change in stress state than 0.35, showing a greater change in permeability coefficient and capillary water absorption. The research can provide an important basis for the design and construction of concrete face rockfill dam panel.