Application On The GPR Forward Simulation And Interpretation Methods For The Leakage Of Underground Water Supply Pipelines In The Urban Area

Water supply pipeline is a critical infrastructure of urban life and economic development. In recent years, due to aging, corrosion and other problems of urban water supply pipelines, it always cause a pipeline seepage. The seepage of water supply pipeline not only waste a lot of water, but also seriously affect the normal life of the people. GPR, as a non-destructive, efficient and accurate subsurface detection tool, which has been widely adopted in disease exploration in the urban pipeline can express the characteristics of the underground disease. However, the traditional interpretation of the data is only based on the subjective judgment of the reflection characteristics and more dependent on technology and experience of the interpreter.For lack of GPR studies in terms of municipal pipelines and to improve the recognition rate of seepage diseases of water supply pipelines, this thesis conducted a series of studies on GPR pipeline seepage disease, the following research works are carried out:(1) Analyze the distribution of seepage areas and seepage characteristics of pipeline disease seepage using Geo-Studio; (2) Calculate the electromagnetic parameters in the seepage area using Topp model; (3) Binding the seepage law and the electromagnetic parameters of the seepage area, this paper compiled model parameters using GprMax forward modeling open source program, conducted two-dimensional forward modeling of seepage areas and obtained disease radar maps under different conditions. Finally analyzed the typical characteristics of seepage area map during GPR image identification judgment process; (4) Further analyzed the electromagnetic properties of radar disease with frequency dividing technology and trace integration, which can highlight the signal of seepage area and improve the recognition rate of GPR data; (5) Finally, we verified the effectiveness of forward simulation and GPR analysis technology of property by field test of pipeline seepage。Through the study above, main conclusions are as follows:(1) It will form a range of seepage area around seepage points when the pipeline seepage disease occurs. Morphological characteristics of seepage area is an increasing range of circular shaped area over time. The soil in central seepage area is saturated soil and the seepage area at the edge portion belongs to a series of zonal distribution of the unsaturated zone. Proposed morphological characteristics in different soil characteristics, different pipeline diameters, different seepage sites and the different location.(2) In the sandy soil, the distribution of soil permittivity and conductivity and soil moisture content has a strong correlation. It can be calculated by Topp model between soil moisture and dielectric constant consistent with cubic function relationship, also a cubic function relationship between soil moisture and conductivity.(3) From the forward modeling of pipeline seepage disease. GPR can effectively reflect the location and the seepage extent of the underground pipeline. We can visually determine the pipeline seepage location through different pattern recognition, but the traditional GPR signal interpretation for characterization of pipeline and seepage areas is inadequate, also it can’t effectively evaluate the degree of seepage.(4) Trace integration technology can improve the overall resolution of the data, highlights the changes in wave impedance of the seepage area and realize the evaluation of different levels of seepage; S transform frequency dividing technology eliminate interference from other noise, portray the seepage degree of different frequency bands; A comprehensive analysis of two attributes can have a more comprehensive portray and judgment of pipeline seepage location and size. Two attributes approachs in the field and forward analysis have been well validated.Based on the above findings:The electromagnetic forward modeling of pipeline seepage disease, and through comprehensive processing analysis of two attributes technology, we can identify the seepage location and specifications of the pipeline more accurately, which provides a new idea to detect pipeline leaks disease.