Numerical Simulation Research On Testing Pile Foundation Integrity Based On DTS

In recent years,large-scale projects have been widely used due to the huge bearing capacity of pile foundations and the special nature of carrying complex loads.The pile foundation project belongs to the underground concealed project,which is difficult to control the construction quality.Nearly one-fifth of the pile foundation has quality defects during the construction process.Studying the application of DTS in pile foundation integrity testing has great economic significance for improving pile foundation quality and saving construction time.This thesis introduces the basic theory and technology of fiber-optic temperature measurement technology to detect the integrity of pile foundation.Based on the existing research,the experimental research on the influence range of fiber-optic pile model is carried out.In this paper,the physical model test and the numerical model test method are used to study the optimization of the optical fiber detection system for DTS detection of the integrity of the cast-in-place pile.The physical model test and numerical model test comparison analysis and research of the cast-in-situ pile integrity are carried out.At the same time,for the two models with and without reinforcement,the heat conduction simulation and analysis of the central line heat source heat conduction and the U-shaped fiber are heated respectively.The steel cage model and the non-reinforcing cage model are compared and analyzed,and the steel cage is explored.The impact of fiber inspection on pile integrity.The main research results are as follows:(1)The higher the heating power,the higher the centerline temperature,and the larger the critical radius of the fiber heat source;the closer to the centerline heat source,the higher the temperature rise.The boundary conditions are different,the temperature rise at the same distance from the heat source is different,and the critical radius of the fiber is different.(2)Fiber structure has a significant impact on heat transfer characteristics.When the fiber length of 28 m is heated by the power of 2w/m-8w/m,the spacing of the U-shaped fiber is about 48 cm.(3)The numerical model is in good agreement with the physical model test results,and can supplement the deficiencies of the physical model test well.The research results and methods provide theoretical basis and technical guidance for the design of the detection system for DTS detection of bored pile integrity.(4)The steel cage structure has a certain influence on the integrity of the fiber monitoring pile foundation.Binding the fiber to the inside of the steel cage is more convenient for temperature monitoring and avoids the interference of the steel bar to the temperature measurement.Regarding the influence of the reinforcement cage on the integrity monitoring of the pile foundation and the optimization of the fiber layout,it is necessary to carry out three-dimensional simulation in combination with the actual reinforcement cage structure modeling.