Experimental Research On Quality Defect Bored Pile Detection Based On Optical Fiber Temperature Measurement Technology

Piles have been widely used in the construction field by its simple construction,pile capacity,high stability,and the length of the pile can be changed with the bearing stratum,without cut pile,no joints.But the requirements of the piles' construction technology are relatively high,at the time of its construction is prone to necking,mixed with clay,broken piles and concrete segregation and the other quality problems.Currently the pile foundation detection methods of the engineering's field have low efficiency,is expensive,heavy and large equipment and can not be real-time detection,and other issues.With the engineering development of detection technology advancement needs of distributed optical fiber temperature sensing technology has many advantages and have been proposed and applied and Piling Quality.In this paper,the case study of the formation of pile quality defects,proposed the use of the heat transfer theory and the sensing fiber is embedded inside the pile,the use of optical fiber temperature sensing technology to detect pile integrity.This text is to study the theoretical basis of the method,and to research the feasibility of the method.Produced different situations pile model tests and been testing,the results are as follows:(1)The current situation of pile by using each detection methods have been analyzed.Comparative advantages and disadvantages of the feasibility of the current pile testing technology,the sensor fiber is proposed to detect the piles' integrity.Research and analysis of the theoretical basis and principles of fiber optic sensors to detect pile quality defects.(2)The model test of the piles mixed with clay have been made.The amount of the piles mixed with clay of each model were: 0,20%,40%,60%,80% and 100%.Regulating the heating power of each instrument model pile was heated fiber and detecting temperature rise of each model pile.The law of each model pile fiber temperature rise has been studied,heating power and fiber the analysis showed that the heating power has a good linear relationship with temperature rise.The influence of the temperature rise of the sensor fiber with the different amount of mud in piles has been analyzed.Tests showed that with the increase of temperature sensing fiber-containing clay content increases.(3)Three difference test model piles of water-cement ratio have been produced,each pile's model of water-cement ratio is 0.38,0.48,0.58.The fiber in each model pile has been heated,and the temperature rise of the sensor fiber has been detected.The law of the temperature rise of the fiber in each test pile has been studied,the analysis show that sensing optical fiber temperature with heating power values are good linear relationship.The effects of the sensing fiber in each model pile with the different water-cement ratio values has been studied,the analysis found that the temperature rise of the sensing fiber becomes larger as the water-cement ratio value increases.(4)Produced a field model test of the piles.The fiber inside the pile was heatedby using a variety of heating power,and the temperature rise within the pile and outside the pile has been detected.The law of the temperature rise of the fiber in each model text with the heating power and the heating time has been researched.The analysis show that the segment mixed with clay of the temperature rise is higher than the normal segment,and the greater the heating power the greater the heating temperature rise of the optical fiber,the temperature trend of the optical fiber gradually slowed last stabilized as the heating time.