The fiber Bragg grating (FBG) sensor is an important tool to measure the surface strain of geogrid. There is a strain transfer coefficient between the real strain of geogrid and the strain measured by FBG sensor due to the existence of adhesive layer. In this study

by taking surface-bonded bare fiber Bragg grating as the research object

the strain transfer formula between fiber layer and matrix layer is derived by establishing the theoretical model of fiber layer

adhesive layer and matrix layer. In addition

the effects of material parameters on the strain transfer coefficient and the average strain transfer coefficient are analyzed. Then

through laboratory tensile test and verification test

the correctness of this newly proposed theory for strain transfer is verified. The results show that the maximum error between the measured value and the theoretical value is about 15%. According to the parameter analysis

the influence of different material parameters on the average strain transfer coefficient can be arranged in a descending order as follows: the FBG bond length

the thickness of the adhesive layer

the shear modulus of the matrix layer

the width of adhesive layer and the shear modulus of adhesive layer

accounting for 33%

23%

20%

13% and 11% respectively.