基于非结构网格的电阻率三维正反演及其应用研究

发布时间：2018-01-26 08:38

本文关键词： 非结构网格电阻率三维正演有限单元法巷道超前探测蒙特卡罗方法三维反演地形　出处：《中国科学技术大学》2016年博士论文　论文类型：学位论文

【摘要】：地表起伏地形在野外矿产资源勘察中不可避免,其对直流电法勘探影响巨大。我们通过在电阻率三维正演中采用非结构网格,能够进行任意复杂地形和几何模型的数值模拟。与结构化网格相比,非结构网格具有可局部加密的特点,只需要在重点观测计算区域内添加有限数量的节点,即可充分发挥有限单元法的优势,在减少计算量的同时,大幅度提高求解精度。球体和无限大板体模型的电阻率三维非结构有限单元数值模拟结果表明,误差均在0.9%以内。不同起伏地形模型的电阻率三维非结构有限单元数值模拟结果表明,地形影响巨大,甚至掩盖地下真实异常体的响应。快速、精确的电阻率三维非结构有限单元数值模拟为其在巷道超前探测中的应用及带地形电阻率三维反演奠定坚实基础。直流电阻率法通过观测单极-偶极装置(三极装置)视电阻率曲线最小值位置估计掌子面前方低阻异常体距离,在巷道超前探测及矿井水害预测与防治工作中有广泛应用。由于地下巷道本身即是三维模型,必须应用电阻率三维数值模拟才能获得地下复杂结构的全空间三维地电场的分布特征。我们基于电阻率三维非结构有限单元数值模拟,给出低阻异常体超前探测的线性预测模型。然而,实际井下地质结构复杂,异常大小不定且任意分布,而且可能存在有电阻率各向异性,使得目前由简单模型实验或数值模拟获得的预测公式不确定性较大,而且可靠性难于评价。蒙特卡罗方法用随机化思想解决非确定性问题,我们将该方法与并行算法结合,对大量不确定的随机模型进行三维数值模拟,以验证各预测模型的准确度及可靠性。结果表明,本文提出的超前探线性预测模型较其他预测模型更为准确、可靠。同时,模拟结果表明介质各向异性的影响很大,尤其当围岩电阻率具有各向异性时,所有预测模型的准确度及可靠性较差,给安全生产带来很大隐患。我们首次将并行蒙特卡罗方法应用于直流电阻率巷道超前探测研究,为巷道超前探测准确性和可靠性的定量化描述提供了新思路。现阶段,面向实际应用的起伏地形下电阻率三维反演依然困难。考虑到应用GPS/GNSS定位技术时,区域地球物理调查中可非规则布设测网的实际特点,我们在基于非结构网格的电阻率三维正演数值模拟基础上,首次实现了任意偶极-偶极观测数据的电阻率、激发极化三维带地形反演。任意偶极-偶极观测方式有效实现大规模、随机化、高密度的三维观测数据采集,同时,非结构网格为地形建模采集地表高程数据及其灵活、高效的野外电阻率三维数据解释创造了有利条件。理论模型合成数据的带地形电阻率、激发极化三维反演结果表明,无论常规的中间梯度数据、还是任意偶极-偶极数据均取得良好反演效果,起伏地形下的不同异常体电性反映清晰、定位准确。通过不断调整合成观测数据中高斯噪声大小,展示了本文的反演方法对不同质量观测数据的反演效果,显示了对噪声的良好兼容性,是电阻率三维反演应用于实际勘探的关键。我们将本文的反演方法应用于甘肃某地的多金属矿三维勘察,对实际观测的电阻率三维数据进行反演解释,给出了矿区的地下电性三维分布,其中一个低阻异常体与正在开采的金矿体吻合,其余三个低阻异常推断为隐伏矿体,以待其它勘探手段查证。电阻率三维反演解释成功应用于实际矿产资源勘探的结果国内、外尚不多见,是实际电法勘探三维反演解释向前推进的重要一步。
[Abstract]:The surface topography in the field of mineral resources exploration is inevitable, the electrical prospecting has great impact. We passed in 3-D resistivity forward using unstructured grid, numerical simulation can be arbitrary complex terrain and geometric model. Compared with the structured meshes, unstructured grid has the characteristics of partial encryption, only need to calculate the node area in addition a limited number of observations in the key, can give full play to the advantages of the finite element method, to reduce the amount of computation at the same time, greatly improve the accuracy of solution. The sphere and the infinite plate model of the electrical resistivity of three-dimensional unstructured finite element numerical simulation results show that the errors are within 0.9%. The resistivity of three-dimensional unstructured finite element numerical different terrain model simulation results show that the terrain impact response and even obscure the real underground abnormal body. Fast, accurate resistivity Numerical simulation of three-dimensional unstructured finite element for its application in tunnel in advance in the detection of terrain and 3D resistivity inversion and lay a solid foundation. The DC resistivity observation by pole dipole device (transistor device) apparent resistivity curve minimum position estimation in front of the tunnel face low resistivity body distance in tunnel in advance are widely used in detection and prediction mine water disaster and prevention work. Because the underground roadway itself is a three-dimensional model must be applied to get 3D resistivity 3-D numerical simulation to the whole space of underground complex structure of electric field distribution. Our numerical simulation of 3-D resistivity structure based on linear non finite element, given the low resistance abnormal body advanced detection model. However, the actual underground the geological structure is complex, the abnormal size is uncertain and arbitrary distribution, but there may be a resistivity anisotropy, making the current by Jane Single model test or numerical simulation prediction formula for the uncertainty and reliability evaluation. The Monte Carlo method to solving the uncertain problems with random thoughts, we will combine with the method of parallel algorithm, a large number of uncertain stochastic model of three-dimensional numerical simulation, to verify the accuracy and reliability of the prediction model. The results show that in this paper, the advance on linear prediction model than other prediction model is more accurate and reliable. At the same time, the simulation results show that the influence of anisotropy, especially when the rock resistivity is anisotropic, accuracy and poor reliability of all forecasting models, bring great hidden trouble to the safe production. We will be the first application of parallel Monte Carlo method in the DC resistivity in advanced detection research, provides a quantitative detection for the roadway ahead of the accuracy and reliability of New ideas. At this stage, 3-D resistivity inversion topography and the practical application is still difficult. Considering the application of GPS/GNSS positioning technology, the actual characteristics of irregular measuring network layout can be the regional geophysical survey, we in resistivity based on unstructured grids of 3D numerical modeling based on first realized arbitrary dipole resistivity dipole induced polarization observation data, three-dimensional topography inversion. Arbitrary dipole dipole observation way of effective implementation of large-scale, randomized, 3-D high density data acquisition, at the same time, the unstructured grid for terrain modeling and data acquisition of surface elevation and flexible 3D field resistivity data interpretation, and create favorable conditions. The theoretical model of synthetic data the terrain with 3D resistivity, induced polarization inversion results show that both the conventional intermediate gradient data, or arbitrary dipole dipole number According to the good inversion effect, undulating terrain under different electric anomalies reflect clear, accurate positioning. By continuously adjusting the Gauss noise synthesis data size, showing the effect of the inversion inversion method for different quality observation data, showing good compatibility to the noise, the key is applied to 3-D resistivity inversion we will survey and exploration. The 3D multi metal mine inversion method in this paper was used to in Gansu, inversion interpretation of 3D resistivity data of actual observations, given the mine underground electric distribution in which a low resistivity body and gold mining is consistent, the remaining three low resistivity anomaly for for concealed orebodies, other exploration methods verified. 3D resistivity inversion applied to explain the results of domestic mineral resources exploration, is rare, is the actual power The three dimensional inversion of the method of exploration is an important step forward.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P631.322

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