Displacement Monitoring And Stability Evaluation Of Diaoshuiyan Slope Based On Fiber Grating Sensor

Studies on slope stability are always the core problems of the geotechnical engineering field.The safeties of human being's lives and possessions,and sometimes even the development of the national economy and society,are relative to the steady status of slopes.It is very important to focus on the slope safety monitoring and forecasting in order to minimize the damage caused by landslide.Traditional slope monitoring techniques have some limitations including low accuracy,poor durability,and difficulty of integration.Possessing several advantages such as long-distance signal transmission,anti-electromagnetic interference and long-term durability etc,optical fiber sensing techniques have been rapidly applied in monitoring the highway slopes in recent years.A new kind of optical fiber grating inclinometer is utilized to monitor the deep displacement of the Diaoshuiyan slope in this paper.Based on the model of cantilever with uniform cross-sections,a polynomial fitting method presented in this paper for the first time,along with the finite difference method proposed by previous researcher,are employed to convert strain of the inclinometer into deep displacement in the slope.By comparing the results of these two methods with that of FEM numerical simulation and scaled experiment,it is shown that both of these two methods can realize the conversion between the strain of inclinometer and deep displacement in engineering.Relatively speaking,the polynomial fitting method has a higher precision than the finite difference method.Furthermore,the finite difference method is not particularly economical because it needs enough sensor measurement points.Therefore the polynomial fitting method is selected as the main converting method in the real time online monitoring system of the Diaoshuiyan slope,and the finite difference method as the supplementary approach.Then the software ANSYS is used to establish the finite element model of the Diaoshuiyan slope,the strength reduction FEM is applied to simulate and analyze the process of deformation and failure of this slope,its critical displacement field is finally acquired.The horizontal displacement mutation characteristics of feature points are chosen as the main slope failure criteria to determine the safety factor of slope stability.Plastic strain zone connection criterion can be used as a reference of the above criteria.The horizontal displacement nephogram and the plastic zone figure have guiding significance to determine the reasonable positions of inclinometer.Through analyzing the trend of the reduction factor-horizontal displacement curve,the authentic threshold can be worked out to help people predict and alarm the landslide.At last,following the design concept of long-term structural health monitoring system and Internet of Things technology,skeleton of the slope's real-time online stability-monitoring network system is successfully built up.The slope stability monitoring and forecasting system,which consists of data acquisition,data transmission and data assessment management subsystems,is real-time,highly effective,open and easy to visit.It can also protect information by rights management.The slope stability safety factor,displacement threshold and displacement increasing rate are adopted as the main assessment criteria to evaluate the stability of Diaoshuiyan slope.In addition,before the slope is unstable,some symptoms captured during inspection can be considered as a reference.Preliminarily,real-time monitoring and early stability warning of the high Diaoshuiyan slope has been realized in this paper.