Internal deformation characteristics of soil samples in additive manufacturing based on FBG technology

In this study, the Fiber Bragg Grating (FBG) sensors are successfully mounted into 3D printed soil samples to investigate the internal strain characteristics in different printing stages, which mainly consist of 3D printing stage, indoor drying stage, and uniaxial compression test stage. The systematic change in infill density including 40%, 60%, 80% and 100% is taken into account in the printing stage. The test results show that the soil printed by the additive manufacturing technology can be divided into three typical stages according to the internal deformation characteristics measured by the FBG sensors, including lateral expansion stage, soil sample drying and contraction stage, and stable residual deformation stage. It is found that: (1) During the printing stage, the lateral strain of soil samples increases, linearly proportional to the change in the infill density. The strain increment of the soil with infill density of 100% is 4 times that with infill density of 40%. (2) During the drying stage, the printed soil samples contract significantly along with a stable strain change phase. The increase of infill density of soil leads to substantial rise of shrinkage strain, and presence of residual strain is postponed when the infill density is high. (3) During the uniaxial compression test stage, the lateral deformation of soil shows a sudden rise, and the measured lateral deformation is linearly proportional to the change in the infill density. The results of the FBG sensors indicate that lateral failure strain of soil increases 1.1 times when the infill density increases from 40% to 100%.