Monitoring Technology Of Geogrid Reinforced Slope Based On BOTDA

The distributed optical fiber sensing monitoring method overcomes the shortcomings of traditional point sensing monitoring,and is a new kind of monitoring tool which can realize continuous monitoring.Using the sensitivity of optical fiber to temperature and strain,the change of physical quantity at any point can be determined according to the frequency change of brillouin scattering light when optical fiber embedded in the structure or soil.Therefore,it is necessary to study the effective and reliable immediate monitoring method.Based on Brillouin Optical Time Domain Analysis,a new distributed fiber-geogrid sensor was proposed.Due to the good compatibility among soil,geogrid and optical fiber,the optical fiber could be inserted into the geogrid to monitor the internal strain of the soil.The effects of different adhesive modes and adhesive thickness on the strain transfer coefficient of optical fiber in distributed fiber-geogrid sensor were studied by ABAQUS simulation.The relationship between the horizontal strain and stability coefficient of the slope was analyzed comparing the unreinforced and reinforced slope model by finite element analysis.Home-made distributed fiber-geogrid sensor was used to monitor the stability of the indoor slope model.Comparing the test result with the simulated results of ABAQUS,the following conclusions are obtained:(1)The distributed fiber-geogrid sensor proposed was based on brillouin optical time domain analysis,which was a new kind of method to monitor the internal strain of soil.Different adhesive modes and adhesive thickness would affect the strain transfer efficiency of fiber.(2)The unreinforced and geogrid reinforced slope model were established by ABAQUS,and the reinforcement effect of geogrids in slope protection was expounded respectively from the safety coefficient,the potential slip surface and the distribution of slope horizontal strain.(3)The relationship between the horizontal strain and safety coefficient of slope was established by means of finite element simulation,and a feasible method to evaluate slope stability was put forward.(4)Comparing the indoor test result with the finite element simulated result,the strain obtained by indoor test was almost lower than that of finite element simulation,especially at the peak of the strain,which would cause a certain error to the slope strain characteristic values.