Research On Deformation Self-sensing Monitoring Of Subgrade Strengthened By A Geogrid Surface-bonded Weak FBG Under Earthquake

China is in the stage of vigorous economic development,and road construction is in full swing.As an important part of road engineering-roadbed-there are often some geological disasters during construction and normal use,resulting in large economic losses and casualties.In addition,the frequent occurrence of earthquakes in China has also brought more concurrent disasters to the roadbed slope.In recent years,with the continuous promotion of the concept of “smart city” in the country,the requirements for intelligence and informationization of monitoring are higher,while the traditional roadbed slope monitoring wastes more manpower,material resources and financial resources,and has poor real-time performance.The requirements of the new technology are urgently needed.As a reinforced material,geogrid is often buried in the embankment slope to increase the tensile strength of the soil and coordinate deformation with the soil to achieve the effect of reinforcing the slope.As a new type of engineering monitoring technology,weak FBG is favored by many researchers because of its intelligence,large data storage,simple operation,simple information processing and less interference from the external environment.Based on this,the geogrid reinforcement technology and weak FBG technology are used to make a Geogrid Surface-bonded Weak FBG,which is used to reinforce the embankment slope under seismic loading and realize real-time monitoring of subgrade deformation.Through theoretical analysis,formula derivation,calibration test,numerical simulation and model test,the fabrication method,information processing formula and temperature compensation technology of a Geogrid Surface-bonded Weak FBG are proposed.The numerical simulation is used to explore the reinforcement effect of a Geogrid Surface-bonded Weak FBG.The location of the ribs and the feasibility of monitoring,and further study the reinforcement effect and monitoring effect of the Geogrid Surface-bonded Weak FBG through model tests.The main research work completed is as follows:(1)Combined with geogrid reinforcement technology and weak FBG technology,a Geogrid Surface-bonded Weak FBG was designed.The suitability test of plastic,glass fiber and steel-plastic geogrid for sensor fabrication was carried out.The Geogrid Surface-bonded Weak FBG temperature self-compensation technology is proposed.The relationship between the grating sensing technology signal and the settlement deformation of the Geogrid Surface-bonded Weak FBG is derived by the finite difference method,which provides a basis for the subgrade settlement deformation monitoring.(2)Through the indoor calibration test,the strain sensitivity coefficient of the Geogrid Surface-bonded Weak FBG and the relationship between the curvature of the grid and the wavelength drift are calibrated.The sensing performance of the Geogrid Surface-bonded Weak FBG is explored,and the wavelength drift and strain of the Geogrid Surface-bonded Weak FBG are obtained.The relationship between the values and the correctness of the relationship between the grating sensing signal and the settlement deformation.(3)Combined with engineering practice,the dynamic response of reinforced subgrade slope and non-reinforced subgrade slope under seismic loading is analyzed by MIDAS/GTS NX numerical simulation.The reinforcement effect of the Geogrid Surface-bonded Weak FBG is evaluated and intelligent geotechnical engineering is proposed.The grid laying scheme proves that the Geogrid Surface-bonded Weak FBG has the feasibility of combining reinforcement and self-monitoring,laying a foundation for subsequent testing and application.(4)Carrying out the vibration table model test of the indoor reinforced embankment slope,embedding the accelerometer and the Geogrid Surface-bonded Weak FBG in the model,real-time monitoring of the model,re-verifying that the reinforcement effect has weakened the earthquake damage and based on the weak grating sensing technology the Geogrid Surface-bonded Weak FBG achieves the feasibility of reinforcement and self-monitoring.