Abstract: Fiber Bragg grating (FBG) sensing technology has the advantages of high sensitivity, anti-electromagnetic interference and real-time monitoring and has thus attracted increasing attention in the field of civil engineering. However, fully coordinated deformation between the sensor and measured object is difficult to achieve using the traditional external packaging method, and measurement errors are common. Based on 3D printing technology, a type of self-sensing geogrid is developed in this study which realizes fully coordinated deformation between the FBG sensor and tested geogrid. This enables using FBG technology to realize real-time and accurate measurements of geogrid strain directly. The self-sensing geogrid is applied to a model test of an underlying sinkhole roadbed to study the roadbed’s ultimate bearing capacity, top settlement and deformation characteristics under different reinforced layers and spacings. Test results show that the ultimate bearing capacity of the subgrade of the underlying sinkhole can be greatly increased by reinforcement, and the subgrade settlement can be effectively reduced. In addition, the bearing capacity of the subgrade can be increased with an increase in the number of reinforcement layers and a decrease in reinforcement spacing. In the vertical direction, the strain of the grid decreases with an increase in the buried depth of the grid; in the horizontal direction, the strain of the grid decreases to both sides with an increase in the distance from the loading centre. The strain of the top grid decreases with an increase in the number of reinforcement layers and increases with a decrease in reinforcement spacing. Experimental results verify the feasibility of the application of the self-sensing geogrid in monitoring reinforced roadbeds in underlying sinkholes.

Key words: ?ber Bragg grating (FBG) sensing technology, 3D printing, self-sensing geogrid, sinkholes, model test