Detection Of HDPE Membrane Breakage In Double Lining Landfill Based On Magnetic Method

At present,there is no applicable method for the detection of the leakage of the underlayer film of the double liner landfill.Only the landfill with the detection electrode grid laid before can be detected by the electrode grid method.But the cost of laying electrode grids is high and difficult to promote in large-area landfills.Based on the feasibility study of subsurface membrane damage detection in landfills based on magnetic methods,the main research method is to combine the physical characteristics of the landfill and the electromagnetic properties to establish a COMSOL physical model for magnetic detection of landfills.The magnetic field characteristics of the loopholes are analyzed through simulation.Signals and their influence factors and influence laws.Studies have shown that when high-voltage direct current is applied on both sides of the lower HDPE film,the magnetic detection sensor can detect a hole signal in the air above the leak to achieve hole location.The magnetic signals of the loopholes cause changes in the magnetic vectors BX,BY,and BZ and the flux density modes,in which the change tendency of the flux density modulus is the most obvious,and it is insensitive to the direction and is suitable for the leakage detection at the site of the landfill.The magnetic field signal of the leak has the following characteristics: The magnetic flux density model at the leak has obvious changes,showing that the center of the leak has a minimum value and each side has a maximum value.Through the analysis of the influence factors of the magnetic field,the following conclusions are obtained: 1.The higher the current intensity,the stronger the magnetic field signal at the loophole;2.The magnetic field signal of the suspected loophole will be generated by the power supply electrode.The actual detection electrode should be far from the detection area;3.In the range,the greater the distance between the detection sensors,the stronger the measured magnetic field signal of the leak and the greater the leak location error.By analyzing the source and noise characteristics of the landfill noise,the magnetic field noise of the landfill can be removed by using preprocessing,differential filtering and power frequency filtering.The prototype system of the detection system was developed.The site verification was performed in a landfill in Xinjiang.The verification results show that the magnetic layer-based method for detecting the damage of the underlying film inthe landfill is feasible.With a sensor spacing of 1m,the effective detection distance of the ground surface is 1m.