鄂尔多斯煤田火区磁异常随深度变化规律研究
Research on law of magnetic anomaly variation with depth in fire area of Ordos Coalfield
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摘要: 通过对鄂尔多斯煤岩在常温下和升温过程中磁化率变化规律的对比，发现煤岩随温度的升高，磁化率也随之升高，通过X-射线衍射仪对加热前后煤岩的成分对比分析发现引起这种变化规律的主要原因是煤岩在升温过程中其铁磁性矿物成分在发生变化；以此做为引起煤田火区磁异常变化的依据，根据经典点的引力位场和磁位场的理论，以煤层火区为判定典型物理模型，利用泊松公式法根据引力位和磁位之间的泊松关系推导出长方体引力位的二阶导数，积分得到煤田火区磁异常正演关系式，利用Matlab对其进行计算仿真出煤层火区模型的磁异常特征。结果表明：随着埋深的增大，目标体表现出来的磁场强度的极值在不断地减小；而且到接近异常体的范围时强度的突变率也在不断的减小；随着煤田火区埋藏深度的增加，磁异常突变的程度也不断扩大到周围地区。Abstract: By comparing the change law of magnetic susceptibility of Ordos coal rock at normal temperature and during the temperature increase: as the temperature increases, the magnetic susceptibility also increases, and the composition of coal rock before and after heating is analyzed by X-ray diffractometer. It is found that the main reason for this change is that the ferromagnetic mineral composition of coal rock is changing during the heating process. This is used as the basis for the magnetic anomaly changes in the coalfield fire area. According to the theory of the gravitational potential field and magnetic potential field of the classic point, the coal bed fire area is used as a typical physical model to determine, and the Poisson formula method is used to determine the gravitational potential and magnetic potential. The second-order derivative of the cuboid gravitational potential is derived from the Poisson relationship, and the forward relationship of the magnetic anomaly of the coal field fire zone is obtained by integration. The magnetic anomaly characteristics of the coalfield fire zone model are calculated and simulated using Matlab. The results show that: as the depth increases, the extreme value of the magnetic field strength exhibited by the target body continues to decrease; the mutation rate of the intensity decreases continuously as it approaches the range of the anomaly; as the burial depth of the coalfield fire increases, the extent of magnetic anomalies has also continuously expanded to surrounding areas.
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Keywords:
- coal field fire /
- magnetic anomaly /
- magnetic susceptibility /
- mutation /
- buried depth /
- spontaneous combustion /
- fire control
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