Application Research Of Chaotic Ground Penetrating Radar In Underground Pipeline Detection

Urban underground pipelines are responsible for important functions,such as transmitting energy,water supply,and discharging waste liquid.They provide basic guarantee for the daily operation of the city.However,with the rapid development of urban modernization,the urban underground pipeline network becomes more disorderly than before.At the same time,the pipeline management is not standardized and some of the pipelines become old.All of these reasons can cause pipelines accidents during the infrastructure construction,such as power and water outage.And they can even cause fires and explosions.Therefore,effective underground pipelines detection has become an indispensable work in urban underground construction.Ground penetrating radar(GPR)as one of the pipeline detection methods is widely used in urban underground construction,for example,underground pipelines position.Different kinds of waveforms can be used as the transmitting signal in GPR.Among them,GPR based on chaotic signal attracts increasing attention,because it has the advantages of high range resolution,low interception probability,strong anti-interference ability and good electromagnetic compatibility.Furthermore,this type of GPR can overcome the tradeoff between resolution and detection distance.This dissertation studied the application of the chaotic GPR in urban underground pipelines detection.The main research contents are as follows:1.The underground pipelines detection methods and techniques are summarized.The concept,data collection methods,and the classification of the GPR are described in detail.Comparing the different GPR system,we propose a chaotic GPR,which utilize chaotic pulse position modulation(CPPM)signal as the transmitting signal.2.A theory model of chaotic GPR which is used for underground pipeline detection is set up.The positioning and imaging algorithms of chaotic GPR are described in detail.And the characteristics of CPPM signal used for transmitting signal are analyzed.Underground pipelines detection based on chaotic GPR is simulated using XFDTD.From the A-scan,B-scan,and the image after backward projection imaging algorithms,we can clearly see the location and the section shape of the buried pipeline.At the same time,we can distinguish between metal pipelines and non-metal pipelines.The simulation results verify the feasibility of locating the underground pipelines by utilizing the proposed radar system.It has a range resolution of 10 cm.Furthermore,the variation of the peak-to-noise ratio(PNR)with the increase of diameter and buried depth of the pipeline is also studied.3.The chaotic GPR based on CPPM signal is constructed.Utilizing the BP imaging algorithm and average filtering algorithm,we can locate the metal pipeline and plastic pipeline buried in the dry sand in the experiments.The variation of the PNR with the increase of buried depth of the pipeline is also studied.The experimental results are consistent well with the simulation results.