Application Of GPR In Geology Forecast For Tunne

The new tunnel projects are more and more with the rapid development of the national economy. It is very important to discover the geology in front of the tunnel in advance in the process of the tunnel excavation because it can provide quite accurate geology data for the construction, adjust the construction craft in time, reduce and prevent the occurrence of the engineering accidents. The ground penetrating radar gets an extensive application in the geological forecast for tunnel because of its fast scan, simple operation, light weight, high effective shield and intuitionistic image.Commencing from wave equation of the electromagnetic wave and Maxwell equation, this text analyzed the transmission rule and attenuation rule of the radar pulse wave in the geotechnical dielectric, summarized the appearance characteristic of various bad geology bodies in the radar image and developed the following processing system for the GPR probing of the tunnel. The primary study contents are following:1) Various probing methods in the geology forecast for tunnel are summarized systematically, the proper extension and the probing methods are emphasized particularly on, and the status of the GPR in engineering practice is given prominence to.2) The basic theories about the GPR probing are elaborated on including the data collecting technique, the data processing technique and the data explaining technique etc.3) Commencing from the basic theories of the electromagnetic wave, the wave equation of the electromagnetic wave, the electromagnetic field of the dipole antenna, the time field and the space field of the electromagnetic wave are introduced, and the electrical properties of the geotechnical dielectric in high frequency are discussed.4) The rules such as the transmission, the wave speed, the reflection, the refraction, the dispersion and the diffraction of the radar wave are expatiated. The transmission and attenuation rule of the radar pulse wave in different dielectric are analyzed by analyzing the electrical properties of the geotechnical dielectric.5) Take Wangzishi tunnel for example, the appearance characteristic of various bad geology bodies which include the solution cavity, crush belt, containing much water belt, crack dense belt etc in the radar image and the processing and identification method of the radar image are summarized. Wall rock sort is divideddynamically according to the distributing and scale of the bad geology bodies. Compared survey and design and practical project, the probing result has proved very successful.6) The following processing system for the GPR probing of the tunnel is developed using VB.net as foreground development program and using Access2000 as background database. Take the zk24+235 cross-section of the Wangzishi tunnel for example, the function and use method of the system are introduced. The system has strong maneuverability and uses convenient. The accuracy of qualitative analysis of wall rock is high and the system holds strong application value.