Elastic foundation beam unified model for ice and frost damage concrete canal of water delivery under ice cover

With the rapid increase of water consumption by living and industry in cities, the operation of the water-delivery canal is becoming common during the icy period in winter. However, there is still a lack of quantitative method for evaluation of freezing damage that could seriously threaten the normal operation of water-delivery canal. In this paper, the ice and frost damage of ice-covered water-delivery canal was defined as the result of the coupling effect of the static ice pressure on the lining plate and the frost heave of the canal subsoil. In this regard, this study deduced an analytical expression of internal force, stress calculation and anti-crack criterion of lining structure under operating conditions of ice cover. The process of derivation was based on elastic foundation beam theory model for no water delivery canal, and the interaction of ice thrust, ice constraint and frost heaving force of foundation were considered. Through the change of the influence coefficient of static ice load, hydrostatic pressure and the coupling coefficient of freezing load, the internal force and stress distribution of lining structure could be unified under the conditions with or without ice cover and water supply in winter, and thus a unified mechanical model of freezing damage for lining structure of water-delivery canal in cold region could be established to provide a quantitative analysis method for the freezing damage of ice-covered water-delivery canal. In order to ensure the practicability of this study, a trapezoidal lined canal of Xinjiang Manas River Diversion Hydropower Station was took as a prototype. In this area, the lowest temperature was -19oC, the foundation soil of canal was loam, the thickness of concrete lining slope plate was 0.20 m, the concrete strength of slope plate was C20. The distribution of internal force, stress and ice pullout force of lining slabs was analyzed, and then the distribution of maximum bending moment along lining slabs and the location of dangerous section were determined with ice and frost damage. The comparative analysis of internal force and stress calculation of the 3 typical trapezoidal canal freezing damage mechanical models showed that the maximum tensile stress of the cross section was 4.186, 2.447 and 2.208 MPa, respectively. The freezing damage in the case that water delivery canal was ice-free was the most serious, and in the case that the canal of no water delivery was the lightest, while the ice-covered water delivery case was in the middle of the former 2 cases, and there was a big difference among the 3 cases, and the location of lining where freezing damage began to occur was totally different. Therefore, 3 typical operating conditions should be considered comprehensively in the anti-ice and freezing design of trapezoidal canal of water delivery in winter and security under the 3 conditions should be evaluated according to failure law and mechanical model. Based on the minor deformation hypothesis of materials, and a unified mechanical model was established here to calculate and analyze the frost heaving of canal foundation soil and ice load acting on concrete canal. In the future, mechanical model of ice and freezing damage of canal under ice cover should be researched deeply for coupling effect of ice cover life cycle. This study can provide theoretical support for the design of water-delivery canal in cold region, for effectively predicting canal frost failure under different conditions, and has important guiding significance for ensuring the normal operation of water-delivery canal.