Optimal control mechanism of concrete water cooling in hydraulic tunnel lining
Water cooling is widely used in the temperature crack control of lining concrete of hydraulic tunnels in the Three Gorges,Baihetan and other giant hydropower projects.However,the mechanism of water cooling for temperature and crack control still needs to be further optimized.At present,the control parameters of water cooling still refer to the relevant specifications of mass concrete for the initial water flow.Nevertheless,the characteristics of the rapid temperature drop,large time and geometric temperature gradients of thin-wall lined concrete are different from those of mass concrete.Through the 3-D finite element method simulation of concrete temperature fields under different water temperature conditions of water cooling,the influences of water cooling on temperature,thermal stress and thermal crack controls are comprehensively analyzed.It is further proved that the optimal control mechanism of water cooling for thin-wall lining structure concrete is"four controls":adopting the optimal water temperature to control the maximum internal temperature,the maximum internal and external temperature difference and the maximum temperature drop rate most effectively.In this way,the anti-cracking safety factor during the whole construction period can be maximized,and the temperature cracks in the early age and low temperature period in winter can be effectively controlled.
lining concretewater coolingtemperature control and crack preventionoptimal controlnumerical simulation
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