Surface Insulation Effect Feedback Analysis Of Pouring Concrete Based On Distributed Optic Fiber Temperature Measurement

For the concrete dam with split-segment column-like pouring,there are five surfaces of the high concrete pouring exposed to the atmosphere.In the event of extreme weather,any surface may have cracks due to excessive temperature gradient.It has been illustrated that laying an insulation board with a certain thickness on the concrete surface can effectively reduce the influence of the external environment and avoid the cracks on the surface.However,according to the cases of the perspective of several high dams which are under construction in recent years,although surface insulation measures have been taken,surface cracks can still be occurred during the process of construction,which means that under different periods,one insulation measure can not be suitable for different airspaces.The key to solve this kind of problem is that based on the data of field measured temperature,getting the feedback about how the thermal insulation effect on thermal insulation measures.So as to adopt reasonable and effective thermal insulation measures.In this paper,the distributed optical fiber temperature sensing technology is adopted to test the experiment of surface insulation effect at the construction site of dams.This study also explores the changing laws of the temperature when the temperature drops sharply during concrete was pouring and in the case of surface insulation measures are adopted.In addition,it also analyzes the changes of temperature and the effect of surface insulation measures on the temperature changes of pouring concrete.Then,based on the experiment data,the temperature field of concrete pouring is calculated by numerical simulation method,and the accuracy of the calculation model is verified by the measured temperature data.After confirming the high accuracy of the model,the surface tensile stress change of the concrete pouring is analyzed when the temperature is suddenly dropped and the surface insulation measures are taken after pouring.Then,the temperature field and stress field of concrete under different thermal insulation measures are calculated,taking temperature,stress and safety factor of crack resistance as evaluation index.Comparing and analyzing the insulation effect of surface insulation measures at different times,spatial locations,insulation materials and thickness.According to the temperature and meteorological conditions at the location of the Baihetan project,the reasonable surface insulation measures were designed in the intermittent period of pouring.Finally,the proposed temperature control measures were applied to the Baihetan dam,the temperature,stress and crack safety factor of the concrete pouring are compared when surface insulation measures are adopted or not.The results showed that the disturbance depth of daily variation of temperature on the surface temperature of concrete pouring is 0.4m.The temperature drop of 14.3°C has a depth of influence of 0.5m on concrete.The insulation effect of 2cm polyethylene thermal insulation quilt on concrete is remarkable.The influence range of thermal insulation is within 0.4 m from the top of warehouse.However,the surface insulation effect is obviously affected by the insulation material and thickness,the holding time and the heat preservation position.So it is necessary to take effective surface insulation measures to improve the influence of temperature change on the surface temperature and stress.In terms of the design of designing the surface insulation measures,according to the change of the temperature,it is not only necessary to design the insulation materials and thickness,but also to consider the specific implementation time and spatial position of the insulation measures according to the change of the temperature.From the result of the analysis,it is revealed that when the temperature drop sharply,it is crucial to insulate multiple surfaces of the concrete pouring in advance.