Fig. 1. Working principle of the fiber Bragg grating sensor

Fig. 2. Working principle structure of sensors

Fig. 3. Installation of full-section dynamic spoke pressure sensor at pile end

Fig. 4. FBG soil pressure sensor emplacement at pipe top

Fig. 5. FBG sensors installation of pile. (a) Outside pile; (b) inside pile

Fig. 6. Relationship between pile end resistance and driving length of test pile TP2

Fig. 7. Relationship between pile driving pressure obtained by strain sensors and pressure sensors and driving length of test piles TP2 and TP3

Fig. 8. Variation of pile driving pressure obtained by pressure sensors with pile driving length

Fig. 9. Variation of pile end resistance with pile driving length

Fig. 10. Variation of side frictional resistance of inner and outer tube of open test pile TP1 with pile driving length

Fig. 11. Variation of side frictional resistance with pile driving length

Fig. 12. Variation curves of axial force of piles. (a) Inner tube of test pile 1; (b) outer tube of test pile 1; (c) test pile 2; (d) test pile 3

Fig. 13. Variation curves of unit side frictional resistance of piles. (a) Inner tube of test pile 1; (b) outer tube of test pile 1; (c) test pile 2; (d) test pile 3