Research On The Forward Simulation Of Detecting Abnormal Geological Body Wihich Contain Aboundant Water In Front Of Tunnel Face

Tunnel plays an important role in transportation. With the fast development of high speed railway,high way,submarine tunnel,geologic disaster is always the main influence of tunnel and underground engineering safty, among these disasters,underground water is one of the main factors.Transient Electromagnetic Method is effective in detecting underground water,with combination of geological conditions,water area can be easily confirmed. However,TEM used in underground engineering is diffenent form ground detecting, so carrying out forward simulation of transient electromagnetic field is helpful for us to learn the radiation rule of electromagnetic wave and get more information.On basis of Maxwell equation,author put great emphasis on the two vortices equation of Maxwell equation group,apply K.S.Yee's space grid model,utilize center difference coefficient substitute for the differential coefficient,so we can disperse the spatial continuous variable and obtain the two dimensional time-domain finite-difference equations which is the equation of instantaneous electromagnetic forward simulation. In order to guarantee arithmetic accuracy, author analyzes the numerical stability ,discuss the numerical frequency dispersion of the two-dimension TM electromagnetic wave and deduce numerical stability expression and ideal frequency dispersion relationship. At the same time to prevent the simulation model wave's strong reflection at the truncated boundary, the super absorbing boundary condition is also introduced,make use of that into the self-regulating program written by C++ language,and get good result.At last,calculation on tunnel model is carried out by the self-regulating program,and we also discuss the affecting area of whole-space forward simulation the affect of water volume and parameters to secondary magnetic field.It was proved that FDTD method is effective in engineering besides it has extensive currency in electromagnetic field, we can also use it to solve different problems and object with modification of initial conditions.Therefore the program also has reference value to workers of electromagnetic field.