| Geophysical prospecting method used for the geological forecast to guarantee thesafety of construction, reduce construction accidents and guarantee the constructionprogress is the essential of a job in the process of tunnel excavation. Geophysicalexploration methods nowadays used for tunnel geological forecast can be divided intothe electric prospecting, ground penetrating radar, TSP and the TSP derivatives. AndGPR is widely applied in tunnel geological forecast for its simple operation, highresolution, high efficiency, image intuitive, low influence on the construction in thetunnel excavation. But despite its advantages, GPR technology has some shortage intunnel geological forecast, such as, inevitable interference, denoising technology,irregular operation, GPR parameters setting, and interpretation without standard andso on. So, research on the problems above has very vital significance.This paper collects the domestic and foreign research in tunnel geologicalforecast development and GPR development in tunnel geological forecast. Based onthe actual work in the Qingdao subway tunnel geological forecast, from datacollection to later data processing and preparation of the report, combined with theactual geological data analysis, the actual excavation validation, indoor test andnumerical simulation, summarized the matters of GPR technology in tunnelgeological forecast. For example, GPR application conditions, working principle,parameter establishment, GPR signal composition, characteristics, screeninginterference signals, GPR reflected wave profile features of the typical geologicaldisasters in Qingdao area granite rock. Moreover, based on the engineering case,summarized a set of standardized GPR tunnel geological forecast method. Mainresearch results are as follows:1. Summed up the theoretical foundation of the ground penetrating radarapplication in advance geological forecast. Analyzed characteristics of of the electromagnetic wave propagation in the geological forecast，Summarize theory basisof each parameter selecting in the radar signal acquisition，the interference sources inthe construction site, composition and characteristics of radar signal and screening ofjamming signal characteristics and screening of jamming signal.2. Analyzed the ability of the ground penetrating radar to detect geologicaldisaster in granite area and the applicability of GPR in advance geological forecast.3. Summarized typical abnormality characteristics of fracture zone, dikes, jointfissures, lithology contact with water in GPR profile from the reflected waveamplitude with phase axis, waveform, frequency and phase law of granite area.Formed the ground penetrating radar method of the geological advanced prediction inthe granite area. |
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