Test Of Cement Soil Based On Ground Penetrating Radar And Numerical Simulation Of Disease

Ground penetrating radar(GPR)can be used without loss and continuous scanning,and has the advantages of intuitive display,high precision and high speed.It can be widely used in the field of water conservancy,civil engineering and traffic engineering.However,as cement soil cutoff wall,which is common in water conservancy projects,there are few non-destructive testing,and destructive testing such as excavation and drilling may cause damage to the new engineering structure.The analysis found that this is because there are still many problems that have not been solved in the detection of cement soil,such as cement incorporation ratio,age and so on to the detection accuracy of ground penetrating radar,the interpretation of radar image of cement soil engineering is based on uncertainty.Therefore,it is of great theoretical and practical value to carry out the research on the test of cement soil based on ground penetrating radar and the numerical simulation of common diseases of cement soil engineering.In this paper,ground penetrating radar(GPR)is used for nondestructive testing of cement soil samples with different cement incorporation ratio,study on the variation law of electromagnetic wave velocity in cement soil sample with different cement incorporation ratios(8%、12%、16%、20%)and different ages(3d、7d、14d、28d、60d、90d),the dielectric constant is calculated by the wave velocity.On the basis of the analysis,the relationship between compressive strength and dielectric constant of cement soil was studied and the change law of water content of cement soil was studied.Research shows:In the same cement incorporation ratio,the wave velocity increases with age;During the same age,the wave velocity decreases as the cement incorporation ratio increases;The same cement incorporation ratio,the relative permittivity of cement soil decreases with the increase of age.The same age,the relative dielectric constant increases with the increase of cement incorporation ratio;With the same cement ratio,the relative dielectric constant and the unconfined compressive strength were negatively correlated,and the positive correlation was found in the same age;The variation law of water content of cement soil is consistent with the change of relative permittivity;The empirical formula for the detection of soil moisture content by ground penetrating radar is not suitable for the detection of water content of cement soil,need to re-fit the formula.Based on Finite difference time domain method(FDTD),the circular cavity,disengaging and loose disease of cement soil engineering was studied by numerical simulation.Research shows:The intensity of the reflected of the air filling cavity is the strongest,the water filling cavity is the second,the mud is the weakest and the reflection coefficient of the medium determines the reflection intensity.The vertical resolution is related not only to the center frequency of the antenna,to the dielectric constant of the medium,but also to the medium contained in the disengaging.The loose radar waveform is scattered,and does not have the characteristics of the in-phase axis.In the radar profile,the range of the air filling loose is smaller than that of the water filling.