Research On The Influence Of Pile Surrounding Environment On The Integrity Detection Of DTS Thermal Method Pile Body

In recent years,the research focus of pile foundation detection at home and abroad is how to use the temperature of pile body to reflect the integrity of pile body.In this paper,based on the existing foundation,a pile heat conduction model considering the physical parameters of the pile surrounding medium was established.By using the distributed optical fiber temperature sensing technology(DTS),the heat conduction law of the pile was studied by heating the optical fiber embedded in the model pile,considering the pile surrounding medium,and considering the pile-soil interface and the structural characteristics of the optical fiber.Improve the theory of DTS testing pile integrity,the main research results are as follows:(1)Through theoretical analysis,the theoretical temperature distribution curve of the fiber in the pile is obtained and it was found that the difference between the structural characteristics of fiber and the environmental boundary conditions around the pile affects the distribution of temperature field in the pile and the temperature rise curve of the heating fiber to some extent.(2)Through model test and considering the pile-soil interface and the structure characteristics of optical fiber sensor,the results show that the influence of different environmental boundary conditions around the pile on the temperature distribution characteristics in the pile body is obvious.The structure of the fiber metal armor will cause the heat loss of the heating fiber.The higher the heating power,the greater the heat loss.(3)Through the model test of the soil covered around the pile and considering the geotechnical medium,the results show that: When the soil temperature changes greatly,it has a great influence on the heat conduction in the pile.Under the comparison of experiment and theory,it was found that after the soil around the model pile was compacted,the thermal conductivity of the soil was increased and the further contact between the pile and soil interface was enhanced.Therefore,the thermal diffusion of the pile body is accelerated,and the temperature rise of the optical fiber in the pile all shows a downward trend.(4)After the model pile was complete covered with soil and different heating parts and different heat sources in the pile were considered.It was found that in the same medium,the effect of temperature rise of optical fiber with metal armored fiber as heat source was better than that with heating wire as heat source;the temperature rise of optical fiber was very different when heating the center of pile and the reinforcement cage of pile.