横向约束瞬变电磁拟三维反演

一维反演是当前瞬变电磁数据反演的主要方法之一,但一维反演存在剖面连续性差的问题,因而将横向约束引入三维测网瞬变电磁数据的一维反演。考虑到一般情况下实际测点分布并不严格规则,构建了距离加权相邻点横向约束的拟三维反演方法,利用高斯—牛顿法求解,并采用反射系数递推的方法快速求取雅可比矩阵。该方法能对非规则测网数据加入横向约束,提高模型相邻测点的连续性。模型正演数据和实际数据的测试结果验证了该方法的有效性和实用性。

Contrast between 2D inversion and 3D inversion based on 2D high-density resistivity data

The 2D data processing adopted by the high-density resistivity method regards the geological structures as two degrees, which makes the results of the 2D data inversion only an approximate interpretation;the accuracy and effect can not meet the precise requirement of the inversion. Two typical models of the geological bodies were designed, and forward calculation was carried out using finite element method. The forward-modeled profiles were obtained. 1% Gaussian random error was added in the forward models and then 2D and 3D inversions using a high-density resistivity method were undertaken to realistically simulate field data and analyze the sensitivity of the 2D and 3D inversion algorithms to noise. Contrast between the 2D and 3D inversion results of least squares inversion shows that two inversion results of high-density resistivity method all can basically reflect the spatial position of an anomalous body. However, the 3D inversion can more effectively eliminate the influence of interference from Gaussian random error and better reflect the distribution of resistivity in the anomalous bodies. Overall, the 3D inversion was better than 2D inversion in terms of embodying anomalous body positions, morphology and resistivity properties.

高密度电法和地质雷达在安徽某隧道岩溶探测中的应用

为查明安徽某公路隧道上方岩溶发育情况,采用高密度电法、地质雷达与钻探相结合的方案,进行“岩溶发育区—岩溶发育点位”两层级勘察,基于拟三维电阻率断面判定隧道上方岩溶发育区范围,针对岩溶区布设地质雷达测网,圈定地下空洞发育位置及规模,辅以钻孔验证。结果表明,高密度电法拟三维电阻率反演结果可清晰显示岩溶发育位置和岩性变化界面,在此基础上,地质雷达可对浅层岩溶发育位置及规模进行精细勘探。