Research On Temperature Distribution And Crack Control Of Mass Concrete In Raft Foundation Of Super High-rise Building

With the rapid development of China's economy,the infrastructure construction is constantly updating and progressing.Super high-rise buildings and large-scale underground structure projects are emerging one after another,and the use of mass concrete is also increasing.This paper combined the raft foundation mass concrete temperature monitoring test project of a super high-rise building and use the finite element software MIDAS/CIVIL to establish the simulation model of the raft foundation temperature field,and then compared and analyzed the actual test and numerical simulation results.By summarizing the existing experimental projects,according to the irregularity of the foundation,the foundation has different thickness,deep thickness,extremely rich groundwater,and heat storage and moisturizing method,the optimal scheme is proposed.The effectiveness and feasibility of the scheme are verified by monitoring the actual test project and analyzing the final result.It provides a theoretical reference for the temperature control and construction maintenance of the raft foundation mass concrete in the future.The main contents are as follows:(1)By using the finite element software MIDAS/CIVIL,the simulation analysis model of the raft foundation temperature field of the test project is established,and the temperature field at different thicknesses of the raft foundation mass concrete under different insulation measures and mold temperature is analyzed.The final result shows that as the concrete mold temperature decreases,the temperature inside the concrete also decreases.As the thickness of the rubber composite panel increases,the concrete surface temperature increases.(2)Combining numerical simulation and experimental data analysis,the optimal temperature difference control scheme is proposed for different thickness of the raft foundation,namely,the temperature of the mold is 20 °C,and it is respectively adopted 6cm?3cm?3cm rubber-plastic board at B1 area in the depth of 9.35 m,4.5m and 2.7m,at B1 area,and it is respectively adopted 5cm?2cm?2cm rubber-plastic board in the depth of 8.25m?3.4m?2.7m,so that the temperature difference of the inner surface can be controlled within the allowable range.Finally,through the collection of test data,the maximum temperature difference between the B1 and B2 areas is controlled between 20 °C and 25 °C,and there is no temperature crack in the raft foundation.The numerical simulation and the “temperature-time” curve of the field test results are basically the same.(3)Through the real-time monitoring of the temperature during the curing process of the mass concrete of the raft foundation,For the different thickness areas of the raft foundation,the monitoring arrangement scheme of “upper measuring point density,lower measuring point sparse” and “middle measuring point dense,two side measuring points sparse” is adopted,Use the automatic temperature inspection instrument for real-time monitoring,and obtain the temperature changes of the raft foundation.It can be concluded that as the thickness of the raft foundation increases,the maximum temperature of the concrete increases.When the concrete temperature begins to decrease,the temperature drop rate of the top,center and bottom concretes gradually decreases.(4)After collecting and sorting the test data,the actual distribution law of the hydration heat temperature field of the mass concrete of the raft foundation in vertical,horizontal and different thicknesses is analyzed.It can be obtained that the vertical maximum temperature increases with the thickness;the lateral maximum temperature occurs at the center where the heat dissipation is less;as the thickness increases,the maximum temperature is proportional to the thickness,and the temperature drop rate is inversely proportional to the concrete thickness.(5)Combine with the data collected by the on-site pre-embedded stress meter and the stu dy of finite element on temperature stress field,It is found that the temperature stress values d o not exceed the allowable tensile strength of concrete,the stress changes first appear to rise a nd then fall,and finally tend to be stable.