回线源地-空瞬变电磁系统及其在滑坡探测中的应用

Loop source semi-airborne TEM system and its application in landslide detection

中国南方地区地质灾害频发,遭受经济损失巨大,其中滑坡灾害危害最为严重.目前对于复杂地区滑坡地下结构探测方面的研究还存在薄弱环节,还缺少快速可靠的探测地下结构的手段.常规地面地球物理方法在复杂地形条件下存在施工困难的问题.应用数值模拟对比分析了回线源和电性源发射条件下场的分布特征和变化规律,为仪器研制和野外采集方案提供参考.针对滑坡地质灾害调查研制了基于旋翼无人机的回线源地-空瞬变电磁系统.该系统使用旋翼无人机作为飞行平台,目前地面发射机功率为10 kW,最大电压为250 V,最大电流为40 A,发射时基4/10/20 ms可选,下降沿为线性沿,同步方式为晶体+GPS;机载接收机采样率250 kHz,在关断后采集二次场并自动组道叠加,连续点号采集,输入等效噪声0.5μV;空中接收线圈为空心线圈,频率为30 kHz,等效面积3100 m^(2).利用新研发的基于旋翼无人机的回线源地-空瞬变电磁系统在贵州发耳典型滑坡体上开展试验研究.对野外试验中地-空与地面瞬变电磁的实测曲线进行了对比分析.试验结果表明,新研制的地-空瞬变电磁系统稳定可靠,能够快速获取复杂地形条件下小范围内的地电结构,适合于滑坡体地质结构的快速探测.

Geological disasters occur frequently in southern China and they can cause significant economic losses.Landslides are one of the most frequent geological disasters.At present,research still needs to be done in the detection of complex subsurface structure under areas where landslides might occur,and the number of fast and reliable methods used to detect underground structures is limited.Conventional surface geophysical methods face logistical difficulties when carried out in areas with significant topography.The characteristics and distribution patterns of the electromagnetic field excited with loop and galvanic sources are compared and analyzed with numerical simulation,which can facilitate the instrument development and field survey configurations.A loop source semi-aerial transient electromagnetic(TEM)system based on rotor unmanned aerial vehicle(UAV)is developed for the investigation of landslide geological hazards.At present,the power of ground transmitter is 10 kW,with a maximum voltage of 250 V and a maximum current of 40 A.The transmission has a timebase of 4/10/20 ms,with a linear ramp-off stage.Crystal and GPS are used for the synchronization between the transmitter and receivers.The receiver has a sampling rate of 4μs.After the transmitter is switched off,the receiver collects the secondary dB/dt field,and the collected data are automatically stacked continuously collect point numbers.The input equivalent noise of the receiver is 0.5μV.The air receiving coil is a hollow coil with a frequency of 30 kHz and an equivalent area of 3100 m^(2).The new equipment is used to carry out experimental research on the Faer landslide area located in Guizhou province.During the field test,the measured data of semi-airborne and surface TEM are compared and analyzed.The test results show that the newly developed semi-airborne TEM system is stable and reliable,and the geoelectric structure below the complex terrain could be quickly recovered from the measured data.The system is found to be suitable for the rapid detection of landslide geological structure.