The Study On The Characteristics Of Electromagnetic Waves And Their Response Of Unfavorable Geologic Bodies In Banzhulong Tunnel

Engineering geological problems encountered in the increasingly complex and bring a great security risk to the tunnel construction with the rapid development of our social economy and the progress of tunnel engineering technology.We must adopt various methods in front of tunnel face geological conditions timely and accurate prediction.The GPR method with some feature such as accurate,nondestructive,fast and low cost is widely used.But the interpretation of the results depends on the mastery of the physical properties.The length of Banzhulong tunnel is about 2.7km,The design requirements using ground penetrating radar to geological forecast short term.Therefore,In-depth study of the surrounding rock from the Banzhulong tunnel especially geophysical characteristics of bad geological body to improve the reliability and accuracy of detection results has very important significance to ensure the safety of tunnel construction.This article analysis the geophysical characteristics of geotechnical materials and unfavorable geologic bodies.The influence of surrounding water on dielectric and conductivity are discussed.Unfavorable geologic bodies models of different types that based on the FDTD method GPRMAX software was established.The models analysis the phase of the reflection with electromagnetic wave and the traveltime response characteristics of double.To find out the influencing factors Through the comparison of banzhulong tunnel geological radar detection results with the actual situation of the excavation and comprehensive analysis of the electromagnetic propagation characteristics of banzhulong tunnel unfavorable geologic bodies bodyResearch shows that the banzhulong Tunnel in the breeze from the weathered granite,granodiorite of the average dielectric constant is 7.4,7.8;Strong weathering carbonaceous siltstone,strong weathering of carbon in Carbon Weathering quartz sandstone,quartz sandstone,the average dielectric constant of the carbonaceous siltstone is 17.9,13.9,8.8,7.7;the average dielectric constant of the tuff is 8.0.similar rock dielectric constant is related to the degree of weathering,strong weathered rock and the maximum dielectric constant.In the weathered rock of the rock dielectric constant minimum.The surrounding rock water content is increased,the dielectric constant and conductivity increase,electromagnetic wave velocity becomes smaller;the dielectric constant of the greater the difference,the reflection amplitude is larger;the relative size of the dielectric constant determines the positive and negative relationship between reflected wave and direct wave phase,the reflection coefficient is negative,the multiple reflection is obvious.Filling water and mud interface reflection on Karst and direct wave phase contrast,multiple reflection phase and alternately.The broken fault zone of radar wave clutter reflection wave,phase axis fault,energy attenuation,visible arc reflection group;radar wave frequency decreases,the center frequency of joints are relatively scattered.With the development of intensive reflection wave form messy,large amplitude,repeated phenomenon is obvious,and the energy attenuation.The weak interlayer interface reflection is straight,clear,good continuity,the interface reflection wave is clear,the interface reflection wave phase and direct wave instead.