| BHT dam is a double-curved arch dam with low-heat cement concrete.Low-heat cement concrete has the characteristics of low hydration heat,and the performance of concrete in later period is close to or more than that of medium-heat Portland cement,but the early strength of low-heat cement concrete develops slowly,so the temperature control and crack prevention of early-age concrete should be paid attention to.The common temperature control measures of concrete in the practical engineering of mass concrete pouring include cooling water supply,lowering the temperature of concrete entering the warehouse,adjusting concrete gradation,changing concrete pouring method,adding admixture,aggregate cooling and so on.Among these temperature control measures,cooling water is most widely used,that is,cooling water pipes are embedded in the mass concrete,and cooling water pipes take away the heat of hydration inside the concrete.Although cooling water pipes can take away the heat of hydration inside the dam body,if the water parameters are not considered,it will cause temperature cracks in the dam body.Therefore,in this paper,combined with the field test of BHT dam,the cooling water supply measures are optimized by analyzing the influence law between the cooling water supply parameters of the test bin and the internal temperature distribution of mass concrete.The thesis mainly carried out the following research work:(1)The test scheme of temperature gradient monitoring test near the cooling water pipe was designed,and the test fiber was embedded near the first layer of the cooling water pipe in Warehouse 19#-043 and Warehouse 17#-068 in Baihetan.(2)Distributed temperature measuring fiber was used to obtain the concrete temperature data at 0.0m,0.1m,0.2m,0.4m and 0.75 m close to the cooling water pipe.Carries out a comparative analysis on the measured data of the test positions,specific include: the same monitoring location different measuring point temperature has carried on the comparison and analysis,to the same location of different temperature measuring point temperature difference value has carried on the statistical analysis,the concrete temperature difference appears when the largest age different location are analyzed,and the different parts to horizontal and vertical temperature distribution of concrete discrete situation has carried on the statistical analysis,the cooling water flow rate,cooling water temperature of concrete internal temperature’s effect on the distribution of correlation analysis and so on.The basic law of concrete temperature distribution near cooling water pipe is obtained through these analyses.(3)The finite element simulation software ANSYS was used for simulation analysis.Through debugging the calculation model,the temperature data of typical measuring points inside the warehouse and the temperature data of measuring points inside the model are compared to get the calculation model.Some concrete Suggestions are given by changing the water flow parameters of the calculation model.The results show that the most uneven temperature distribution in concrete occurs in the first 7 days after warehouse closing.The positions with the highest and lowest horizontal temperatures are 0.75 m and 0.0m away from the cooling water pipe,and the highest and lowest temperatures are 23.88℃ and 15.44℃,respectively.The correlation coefficients of concrete temperature change caused by water flow and temperature difference at 0.0m,0.1m,0.2m,0.4m and 0.75 m distance from cooling water pipe are-0.928,-0.897,-0.787,-0.513 and-0.252 respectively.It is recommended that the water flow in the first 7 days after warehouse closing should be maintained between 75L/min and 90L/min,and the inlet water temperature should be maintained between 10℃ and 14℃.After 7 days of silo closing,the cooling water flow in the dam can gradually decrease.The rate of decrease of flow is 5 L/min per day.The rate of rise of water temperature can be 0.3℃ every 2～3 days.The water supply temperature should not exceed 14℃. |
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