Research On Detection And Recognition Of Urban Underground Nonmetallic Pipelines Based On GPR

In the construction of urban rail transit,underground pipeline detection is an important link.Due to the imperfect information of the old pipeline network and the information of pipeline network can't be easily shared among various departments,many pipeline damage incidents occurred during the construction process.Therefore,it is necessary to detect underground pipelines accurately to provide technical support for construction activities.In view of the above problems and research status,this paper combines numerical simulation and engineering examples to carry out theoretical and practical research on ground penetrating radar pipeline detection.In this paper,three important control factors in numerical simulation,numerical dispersion,stability of solution and boundary control conditions are discussed.The advantage of PML in boundary effect control is emphasized.Using numerical simulation software GprMax2 D,the urban underground pipeline models under different conditions are built,and the numerical simulation results are output with MATLAB.Numerical simulation results show that: the detection resolution decreases with the increase of the depth at the same central frequency;the inflatable pipeline and the filling pipeline can be distinguished according to the multiple reflection signals under the hyperbolic reflection arc of the pipeline;the resolution of ground penetrating radar is an important factor affecting the detection effect.When the distance between parallel pipelines is small,the simulation results show that it is impossible to distinguish the two pipelines.The hyperbolic reflection arc is gradually separated when the spacing is enlarged.The higher the central frequency of the empirical radar antenna is,the higher the detection resolution is.However,this rule is only valid in a certain detection depth.Forward simulation shows that with the increase of the buried depth,the high frequency antenna can't always detect the simulated pipelines.The upper pipeline will interfere with the detection of the lower pipeline,especially the water-filled pipeline will completely cover up the reflection signal of the lower inflatable pipeline.Based on the numerical simulation,Reasonable detection systems were selected for field test.The results show that the hyperbolic characteristics of radar reflection from pipelines can accurately distinguish inflatable water-filled or non-metallic pipelines;the top of hyperbolic reflection arc of metal pipelines is more "sharp" than that of hyperbolic reflection arc of non-metal pipelines;Resolution can not achieve the theoretical detection resolution,due to the ground penetrating radar is affected by site conditions.Due to the limitation of the function of the numerical simulation software model and the influence of many interference conditions on the test site,the detection of underground pipelines in this paper is insufficient,including multi-layer parallel laying pipelines,calculation of pipe diameter and fine processing and interpretation of data.Figure 39 Table 10 References 100...