Research Of The Loess Embankment Dielectric Parameters Features And Ground Penetrating Radar Echo Forward And Interpreting

In the process of the loess embankment construction,it frequently appears subsidence of fill layer and landslide phenomenon in fill slope.These problems are caused by uneven degree of compaction and uneven saturation.As a result,it seriously affects the security and user productivity of ongoing development buildings.This article adopts the method of Ground Penetrating Radar(GPR)which is a fast nondestructive test method.We take research techniques that indoor test and analytical analysis,numerical simulation and field monitoring test.So it is necessary to make a systemic and deep research on the relative permittivity of loess and its interface transmission and reflection mechanism of the electromagnetic wave and the influencing factors and imaging regularity of GPR.Thus,we established the inversion model of the echo amplitude and the pcrmittivitys based on GPR.Finally,interpretation of image data of GPR and rapidly nondestructive testing of the loess embankment site can be realized.The main achievements and contributions of this dissertation are as follows:1 The relative permittivity and conductivity of the loess are experimented.The inner relationship of relative permittivity of loess and gas liquid solid three phase was analyzed.The mathematical-physical relations were studied among the relative permittivity and conductivity of the loess and relative compaction and moisture content.The relationship between relative permittivity and moisture content in the different antenna frequency of GPR was discussed.2 Reflection amplitude in the special interface of unsaturated loess and the electric field intensity of GPR wave were deduced.Then the regulation and transient characteristics of the reflection and transmission in the different special interfaces were analyzed.And we studied echo intensity characteristics in interface of loess layer of different moisture content and compaction through the numerical methods.Mechanism and regularity of echo imaging on the multilayer filling by the change of the moisture content and compaction in the unsaturate soil were discussed.3 We studied the imaging curve reflection mechanism of the adverse geological body by finite-difference time-domain(FDTD)method of Ground Penetrating Radar.And also,we studied imaging characteristics of target bodies in different geological background,different frequency and resolution of GPR and different depth.At the same time,size,the imaging laws of GPR are analyzed and summarized,which were affected by the size,shape and material of adverse geological body.4 we started with GPR waveform and variation of amplitude,which were affected by the relative dielectric parameters of the detection of grassroots loess.Then we extracted the waveform of testing data by GPR and the reflection coefficient was calculated.We established mathematical relationship between reflection amplitude and permittivity by forward modeling method.And we obtained the optimal solution of electromagnetic wave velocity of every fill layer by conjugate gradient and global optimization method.Therefore,it can be scientifically interpreted the location and geometry of the adverse geological.