Abstract
Two years after the Zhanghewan Pumped-Storage Power Station was put into operation, more than 500 blisters appeared in the asphalt concrete facing of the upper reservoir, and nearly half of them ruptured at the surface. The blistering mechanism of the asphalt concrete facing was studied in this paper. Through on-site inspection and coring inspection, it was found that the blistering was caused by the vapor pressure formed by the water enclosed in the middle of the impervious layer during high temperatures. Numerical analysis showed that the temperature 5 cm below the surface could reach 50–60 °C. Through numerical analysis and model tests, the internal water at this temperature may form a vapor pressure of 20 kPa. Finally, the blister size of the asphalt concrete facing at this temperature and pressure was studied with a model test. The possible sources of moisture inside the impervious layer were also analyzed through a core test, which found that moisture was most likely to be introduced by water spraying during rolling.
Highlights
Asphalt concrete facing is widely used as the water proofing lining for reservoirs [1,2]
Through on-site observation and laboratory tests, the following conclusions can be drawn about the blister defects of Zhanghewan asphalt concrete slab: (1) Blisters with a diameter was 5 ~100 cm, gradually appeared after two years of completion of the project, and new blisters are still appearing after ten years of operation
(2) Through the core inspection and the ground penetrating radar test, it was found that the blistering was mainly located in the upper impervious layer, there was no phenomenon whereby the entire upper impervious layer was blistered, indicating that the blistering was not caused by blocking of the drainage layer
Summary
Asphalt concrete facing is widely used as the water proofing lining for reservoirs [1,2]. In November of 2014, exhaust pipes 76 mm in diameter were inserted from the drilling holes into the drainage layer on the top level of the facing to reduce the steam pressure. In order to manage further potential blisters in the operation of the reservoir, the present blisters were investigated and cored on-site, and models were experimented with in the laboratory and studied, as described in this paper, to clarify the cause of the blisters. This information could be referenced by other projects
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