Test Study Of Complex Underground Pipeline Detection In Urban Residential Area

With the rapid development of China's urban modernization,the underground pipe network of each city is becoming more and more complex,and the complexity of pipe network type is increasing rapidly.Although the investigation and digitalization of the main pipe network of each city have been carried out in recent years along with the construction of " underground pipe gallery",the relevant research on underground pipe network of residential quarters,which is an important part of urban underground pipe network,is still very limited.Due to the characteristics such as limited space,dense population and buildings,various pipeline types,decentralized ownership units,pipeline reconstruction and so on,the distribution of underground pipelines in the residential area is complex and staggered,and the detection is difficult.How to select the appropriate detection method to solve the problem of complex underground pipeline in urban district is the difficulty and focus of urban pipeline detection.Therefore,taking the underground pipeline of three campuses in northwest university as the research object,this study compares and evaluates the applicability of different detection methods under different pipeline distribution and combination schemes for electromagnetic induction,geological radar and acoustic detection,and obtains the detection optimization parameters under different pipeline methods and combined solutions of different methods,and verifies them in an example.The main conclusions of this study are as follows:(1)The electromagnetic induction method is used to test three kinds of complex pipelines including near-distance parallel pipelines,cross pipelines and upper and lower parallel pipelines,and the combination scheme suitable for different pipeline conditions is established.1)Direct method and clamp method are preferred when detecting three types of complex pipelines.2)In the detection of near-distance parallel pipelines,the direct method is not easily affected by adjacent cast iron pipelines,but is easily affected by cable pipelines,and the interference of cable pipelines can be distinguished by signal strength;high emission frequency should be used to detect cast iron pipelines by clamp method,and 65 kHz emission frequency is the best.When induction method is used in detection,oblique line pressing method can suppress the interference of adjacent pipeline,in order to highlight the target pipeline signal.3)In the cross pipeline detection,the abnormal signal should be attached more importance at the intersection of pipline,which is easily misjudged as a pipeline.4)When detecting the upper and lower parallel pipelines,the position of the pipeline can be determined by detecting the overlapping section of the upper and lower pipelines first,but the buried depth of the pipeline can not be determined,and the buried depth of the pipeline needs to be measured and determined at the bifurcation of the pipeline respectively.(2)The geological radar method is used to compare the near-distance parallel pipeline and non-metal pipeline,and the influence of different parameters of geological radar on the detection effect is analyzed.The optimal parameters of geological radar in the near-distance parallel pipeline and non-metal pipeline detection and the combination of parameters in different complex pipeline conditions are determined.1)the higher the frequency of geological radar antenna,the higher the resolution of the pipeline,but shallower the detectable pipeline depth is.It is most appropriate to use a 700 MHZ antenna to detect pipelines with a diameter of ?150mm and a buried depth ? 0.72 m,and it is most effective to use a 250 MHZ antenna to detect pipelines with a diameter of ?200mm and a buried depth ? 1.54 m.The smaller the distance between measuring points,the more underground information is detected,but too much underground information will bury the target pipeline,weaken the signal of the target pipeline,which can not reach the ideal detection effect.When detecting pipelines with a buried depth of 1.1-1.4m and a pipe diameter of 100-150 mm,the best detection effect can be achieved by selecting the measuring point spacing of 0.2m;When detecting cast iron pipelines with a buried depth of 1m and a pipe diameter of 200 mm,the detection effect is best when the antenna spacing is 0.8m.2)The geological radar is used to explore two parallel cast iron pipelines with 100 mm diameter,and the minimum distance of pipeline that can be effectively detected by the radar with 100 MHz antenna frequency is 0.4m;The minimum pipeline spacing that can be effectively detected by a 250 MHz antenna frequency radar is 0.2m.3)Non-metallic pipelines are detected by geological radar.When the radar with antenna frequency of 100 MHz is used to detect the PVC pipelines with a buried depth of 1m,the minimum diameter of pipelines that can be explored is 150mm;when the radar with same antenna frequency is used to detect the PVC pipilines with a diameter of 300 mm,pipelines with buried depth below 1.9m can be explored.And when the radar with antenna frequency of 100 MHz is used to detect the concrete pipes with a diameter of 300 mm,the pipes with buried depth below 1.85 m can be detected;when the radar with the same antenna frequency is used to detect the concrete pipes with buried depth of 1.1m,the pipes with diameters of 150 mm,300mm,or 400 mm can be explored.(3)According to the complex pipeline combination of various materials in the case,the practical and technical process has been preliminarily established combined with engineering cases,and good results have been achieved.Firstly,through obtaining the historical data of the basic information of the plane position,direction,buried depth(or elevation),specification,property,material of the underground pipeline in the residential area,the combination of electromagnetic induction and acoustic detection method is used to detect the metal pipeline,thus determining the connection and location of the pipeline.Then acoustic detection is used to test the detection results.Under the condition that the detection effect of electromagnetic induction and acoustic detection is not ideal,using geological radar to detect underground pipeline can obtain best effect.Finally,it is necessary to open and close the valves and conduct field excavation to verify the effectiveness.The case shows that the three methods cooperate with each other,and verifies each other which can solve some extremely difficult and complex pipeline problem.