Three Dimensional Gpr Reverse Time Migration Method For Engineering Concealment Disease

With the vigorous development of our country's infrastructure construction,a lot of infrastructure works,like roads,railways,dams have come into service period.Because of various reasons like the construction time,design standards,and uneven level of construction technology,as well as complex geology of works,the engineering structure in service always suffer from different problems.Cracking,leakage and collapse and other accidents happens now and then,which has posed great challenges for the long term and stable operation of infrastructures.Accurate detection of hidden engineering structure problems.is the precondition for diagnosis and control of engineering safety state.However,the normal ground penetrating radar detection is mostly two-dimensional,which can only detect the existence of hidden problems,but hard to provide three-dimensional spatial location and other accurate information.Regarding to the above problem,this paper introduces the GPR three-dimensional reverse time migration imaging method into engineering concealment disease.Meanwhile,regarding to the problem of large demand for wavefield storage in three-dimensional reverse time migration imaging,storage boundary and wave field reconstruction method is taken to reduce memory consumption.Moreover,regarding to the problem of low calculating efficiency of and long time consumption of three-dimensional reverse time migration,GPU parallel acceleration method based on CUDA architecture is realized.On such a basis,take the tunnel linings and dam problems as examples,generalize several kinds of typical problems,and carry out systematic study on forward modeling and migration imaging.And on this basis,study on imaging model test of engineering concealment disease is carried out,and then the method in this paper is verified as effective and practical in application of actual field testThe main research work and achievements of this paper are as follows:(1)Improved GPR 3-D reverse time migration method based on deep illumination and wave field reconstruction.3-D FDTD forward modeling program is written.Meantime,regarding to the problem of excessive memory required for calculation because full-time full-wave field values need to be stored in cross-correlation imaging conditions of reverse time migration,this paper takes effective internal boundary storage strategy.In the process of forward propagation of wave field of shot point,only last-minute full-wave field and intermediate-time internal boundary wave field are stored.And last-minute full-wave field and intermediate-time internal boundary wave field is taken as boundary condition to calculate accurate internal wave field information during wave field back propagation.This has reduced memory storage greatly.Regarding of the problem of insufficient amplitude deep imaging region in reverse time migration imaging results,according to the deep lighting method in earthquake detection,this article use energy matrix depth lighting to improve the result of cross-correlation imaging method,which has improve the imaging quality of deep region.(2)GPU acceleration method based on CUDA architecture.In view of the problem of long time consumption of three-dimensional FDTD and reverse time migration imaging,this paper puts forward GPU program acceleration strategy based on CUDA By using the natural parallelism of FDTD process and the advantage of GPU in processing massive and highly parallelized data,this paper studies GPU forward modeling acceleration and migration imaging acceleration method.Moreover,based on the characteristics of CUDA architecture,optimize the acceleration program and improve the calculating efficiency of program,with computing speed being 40 times faster than CPU version.(3)Carry out systematic study 3-D forward modeling of GPR and reverse time migration imaging in view of typical engineering problems.This paper focuses on engineering problems of tunnel linings and dams,generalizes common problems types,and establish 3-D geologic model of engineering problems,carries out systematic study 3-D forward modeling of GPR and reverse time migration imaging on engineering concealment disease,generalizes the forward modeling and migration imaging characteristics of typical engineering concealment diseases,which provide basis for practical engineering application(4)Study on engineering concealment disease,model test and actual detection test.This paper establish three kinds of actual model,including voids,pipes,cracks.Besides,We collects data,and carries out in-room test of 3-D reverse time migration imaging,and imaging result basically matches with the initial prefabrication model.