论文部分内容阅读
描述和估计介质含水量、介电常数等属性参数分布是探地雷达探测技术的重要研究内容。雷达波的旅行时间和反射振幅系数与介质含水量、孔隙度与介电常数密切相关。常规通过旅行时间计算波速以估计介质参数的方法,例如透射波法,共中心点速度分析等,对于复杂介质分辨率有限。基于反射振幅的阻抗反演方法可以直接根据反射系数计算雷达波阻抗以估计介质属性参数,从而有效地避开常规方法在计算波速时精度低的问题。本文首先建立了基于高斯型和指数型混合自相关函数的三维多尺度等效随机介质模型刻画地下随机介质参数分布,并在局部加入高斯椭圆方程描述局部随机异常目标体。其次,通过引入锥形函数以降低随机介质模型在离散网格数值计算方法误差。在此基础上,推导了探地雷达递推阻抗反演的基本流程并结合随机介质模型测试了该方法在复杂介质参数估计中的计算精度。最后,对内蒙地区的实测探地雷达数据利用递推阻抗反演方法来估计地下污染物参数,估计介电常数、含水量结果与钻孔实测数据和同期开展的电阻率成像结果有很好的吻合。说明基于递推阻抗反演方法在探地雷达复杂介质属性参数估计中具有很好的应用前景。
Describing and estimating the distribution of attribute parameters such as water content and permittivity is an important research content of GPR detection technology. Travel time and reflection amplitude coefficient of radar wave are closely related to medium moisture content, porosity and dielectric constant. Conventional methods of calculating wave velocities by travel time to estimate media parameters, such as transmission wave methods, point-centric velocity analysis, etc., have limited resolution for complex media. The impedance inversion method based on reflection amplitude can directly calculate the radar wave impedance based on the reflection coefficient to estimate the media attribute parameters, so as to effectively avoid the problem of low accuracy when calculating the wave speed by the conventional method. Local established firstly added Gaussian random elliptic equations describe local abnormal target body in the three-dimensional model of the equivalent random medium multiscale self-correlation function based mixed Gaussian and exponential random medium subsurface characterization parameter distribution, and. Secondly, by introducing a taper function to reduce the error of the random medium model in discrete grid numerical calculation method. Based on this, the basic flow of GPR recursive impedance inversion is deduced and the computational accuracy of this method in complex medium parameter estimation is tested with stochastic medium model. Finally, to estimate the parameters of the subsurface contaminants Found GPR data area Inner recursive impedance inversion method, estimating the dielectric constant, moisture content, and the results with the measured data over the same period to carry borehole resistivity imaging result good Anastomosis. It shows that the method based on recursive impedance inversion has a good application prospect in the parameter estimation of GPR complex medium.