Monitoring Research For The Settlement Of Young And Old Subgrades Based On Distributed Optical Fiber Sensing Technology

In road widening works, the settlement is difference between young and old subgrades becauseof different consolidation time, and pavement damage is particularly prone to occur in the junction ofyoung and old roads, it is inconvenience and danger to the traveling vehicles, especially for a tallslope supporting of road widening. So it is necessary to monitor young and old subgrades and gettheir settling regularity. But traditional instruments are mostly point monitoring, they can not providecontinuous time section monitor along subgrade, and high level of automation, small workload.Distributed fiber sensing technology can not only solve these problems, but also have long-range,intelligent monitoring features. Therefore, it is greatly significant to monitor settlement of young andold subgrades based on Brillouin Optical Time Domain Reflectermetry.1. In this paper, according to the optical fiber sensing technology, the temperature and strain oftwo optical fibers were calibrated and the coefficient of temperature and strain were obtained.Through analyzed the sensitivity of the optical fiber, the factors was obtained which affected thesensitivity of the optical fiber.2. In this paper, a kind of monitoring project was designed which can obtain the settlement ofsubgrade based on BOTDR technology.3. Indoor a model of road widening was established, according to monitoring project, two kindsof fiber were buried, combined with a dial indicator to verify the settling feasibility which two kindsof fiber optic monitoring soil, gravel, and verify the deformation ability of optical fiber with geotextilesynchronization. Applied load on the model, every so often the monitoring data of fiber and dialindicator were read, and the settling regularity of young and old subgrades was obtained through theexperimental data analysis.4. According to finite element and road widening parameters, typical engineering sections wereanalyzed to obtain the settling regularity, and the main influential factors of young and old subgradesbased on ABAQUS software.5. The settlement deformation of young and old subgrades was measured by optical fiber andcalculated by finite element show that both are the same.6. According to the finite element simulation results, a number of sections were selected whichsettlement are severe of a road widening project in Qingdao, routine monitoring instruments andsensor cables were buried to verify the feasibility of BOTDR technology in road widening project.