The Study Of Measuring Method For Moisture Absorption And Discharge Of Concrete Structures In Underground Hydropower Station

With China’s economic rise, its demand for energy increases. In recent years, Chinahas presented a strong momentum to develop large-scale hydropower resources. Atpresent, China has the biggest total installed capacity of hydropower in the world.The underground powerhouse has a wider range of applications in the hydropowerprojects which have been built or are under construction in China. Only by controllingair parameters from different spaces in of underground powerhouse in a certain rangecan ensure plant operation with safety, reliable, high efficiency and long life. And bycontrolling air parameters also can minimize accidents and provide staff with healthy,comfortable and safe working environment. However, the research for heat andmoisture transfer calculation theory and the basic data lacked, especially the calculationmethod for the moisture absorption and discharge of enclosure structures. Gaining themoisture absorption and discharge quantity of enclosure structures under differentconditions in the actual engineering by means of measurement is significant toaccumulate basic data and to set up calculation method for the quantity in suchengineering. But at present, the method for determination of the moisture content is verylimited, and it’s difficult to calculate the content in the project site. Thereby, this paperdiscusses a method to calculate the moisture absorption and discharge quantity ofenclosure structures by the determination of related parameters with concrete structureas an example.Based on Whitaker’s volume averaging theory, this paper establishes a theorymodel for heat and moisture transfer through porous material. Then, the relatedparameters of this model are revised and perfected with the method of experiments. Andfinally the numerical calculation model of moisture transfer specifically for concreteenclosure structures is set up. By the way of numerical simulation analysis, the mainfactors which affect the moisture absorption and discharge quantity on the surface ofconcrete enclosure structures are determined. In order to find the relationship betweenthe main influencing factors and the moisture absorption and discharge quantity, thispaper uses this numerical calculation model to do the16sets of numerical simulation toobtain the fitting data. When doing the numerical simulation, the temperature andhumidity fluctuations in the plant of each season along with the temperature differencebetween the surface of enclosure structure and air are fully considered to make sure that the simulation contains most of the actual situation about underground workshop.Finally, large amounts of data are obtained with the method of the simulation analysis.Based on the least squares, the calculation equation for the moisture absorption anddischarge quantity of concrete enclosure structures in underground workshop is fittedusing the data.Independent variables of the equation include the air moisture content, thetemperature of the surface of enclosure structures and volumetric moisture content. Allthese parameters can be measured by using relatively well-developed and convenienttesting methods. With these test values, the moisture absorption and discharge quantityon the surface of the enclosure structure can be found by calculation.