Research Of Leakage Positioning Method Of Landfill Base On Distributed Optical Fiber Temperature Measurement System

At present,the main method of hazardous waste treatment and disposal in the world is safe landfill.In order to prevent the danger to the ecosystem caused by landfill waste,the impermeable layer must be set in the landfill design construction according to the relevant regulations of laws.At present,Chinese landfill sites use HDPE membrane as impervious membrane.However,due to natural or human factors,the HDPE film may be inevitably damaged.As a result of that,the isolation of garbage percolate and soil under the membrane and ground water can't achieve an idea result.So the key to solve the pollute problem of landfill lies in accurately finding the damaged position of the HDPE film and timely repairing.Because of GCL is used in the primary and secondary impermeable layer in the new landfill sites,instead of the clay layer in the traditional landfill,the existing detection techniques all have limitations invariably.As a result,based on optical fiber temperature measurement technology,this paper has proposed the method for detecting and locating the position of leakage by using optical time domain reflectometry.The main contents of this paper are as follows:(1)This paper uses backward Raman scattering from photolysis of fiber temperature signal detection points,combines OTDR detection principle,and constructs the leakage detection model based on optical fiber temperature measurement technology.At same time,we study the feasibility analysis of the method used in landfill leakage detection model,finally we get a detailed study of the OTDR detection principle and the temperature calibration and using heating method to improve the leakage area and non leakage zone temperature to reduce the detection error;(2)We carry out a detailed analysis of the spatial resolution,distributed optical fiber temperature measurement system temperature and time resolution,and the resolution factors;We study the main performance parameters of the OTDR system,including the wavelength,pulse width,average time,dynamic range,blind spots,and the influence of some parameters on the system stability and sensitivity of the optical loss and so on;(3)The distributed optical fiber temperature measurement system for the hardware and software is designed.As to hardware,we design the receiving module,and the Raman scattering of incident light amplifying circuit module,photoelectric conversion,digital analog conversion module and based on USB high speed data acquisition system.By using USB2.0 processor chip CY7C68013 programmable interface GPIF and internal FIFO,we achieve a high speed of data acquisition;We conduct a study based on ARM Cortex-A8 kernel S5PV210 microprocessor control storage and access,human-computer interaction,parameter setting,remote control etc..(4)In this paper,we conduct a detailed study about the filtering of white noise in Stokes scattering and Anti-Stokes scattering by means of filtering methods,such as additive algorithm,wavelet transform and weighted average method.Finally we analyze the advantages and limitations of various algorithms.