采掘扰动岩体破坏自然电场近源效应

Near-source effect of natural electric field responding to mining-induced rock mass destruction

在地下全空间地电场探测工作中,将自然电场对具体岩体动力过程(岩体破坏、地下水渗流、流固耦合演变等)的时域超前感应能力与直流电阻率法、激电法对物性的空间表征能力相结合,有望获取多相耦合系统演化探测及灾变预警的新突破,但须厘清自然电场对不同岩体动力过程的响应机理及特征。为克服跨尺度研究的困难并突破自然电场多种参数(自电位、自然电位、表面电位、感应电荷等)耦合分析的瓶颈,引入了矿山岩体力学相似材料模拟手段;基于对岩体破坏自然电场异常成因的阐述和对岩样加载实验(厘米级)、物理模拟实验(米级)、矿山原位实验(亚千米级)3种尺度的实测成果的系统论述,提出并阐述了采掘扰动岩体破坏自然电场响应过程中的近源效应的内涵、科学意义,同时指出了面向岩体破坏探测的自然电场法研究尚面临的关键问题。3类实测成果共同表明:自然电位的波动幅度、频率、相位都可指示采掘扰动岩体破坏特征,且因自然电场受破裂成因主导,近破裂区(近源区)自然电位的波动与远破裂区(远源区)有所不同,相对表现为高幅、高频、异相,故将其定义为一种近源效应;该效应的物理内涵为:自然电位波动幅度越大(近源区会更大),岩体释放能量越多、岩体破坏程度越高;幅度相当时,频率越高(近源区会更高),破裂事件越频繁,破坏程度越高;相位相异点越多(近源区会相异,远源区多相同),破裂点越多,破坏程度越高。对工程岩体破坏自然电场响应机理的深层揭示须受特定工程场景约束且有赖于多学科交叉研究的深入、模拟水平与测试技术的提升、对非线性信号分析方法的引入等,基于此可推动自然电场法、直流电阻率法、激电法并行探测及多参数特征融合方法的构建,为灾害源智能、精准探测及临灾预警提供新的地电学理论支撑。

In whole-space geoelectric field detection,new breakthroughs may be obtained in multiphase media coupling system evolution detection and disaster early warning as long as the temporal advanced sensing abilities of the natural electric field for specific dynamic processes in rock mass(rock mass destruction,groundwater seepage,fluid-solid coupling evolution,etc.)can be effectively combined with the spatial characterization abilities of direct current resistivity methods and the induced polarization methods,provided that these detection abilities and their mechanisms of the natural electric field are clarified.In this paper,similar material simulation methods in mine rock mechanics field were introduced to overcome the difficulties both of the cross-scale research and the coupling analysis of multiple parameters of natural electric field,including self-potential,spontaneous potential,surface potential,induction charge,et al.The cause of abnormal response of the natural electric field was discussed as well as the experimental results at three different scales,including rock sample loading experiments( cm level),physical simulation experiments( m level),and mine in-situ experiments(sub-km level).Thus,its connotation and scientific significance were put forward and explained of the near-field effect in natural electric field responding to mining-induced rock mass destruction.Additionally,kay problems in further research of natural electric field method(self-potential method) for rock mass destruction detection were pointed out.The experimental results jointly show that the phase,frequency and amplitude of the self-potential signal can all be used to characterize mining-induced rock mass destruction,and compared with far area,it is different in near area of the fracture source with the distinguishing feature as the higher frequencies,bigger amplitudes and different phases.The greater the self-potential amplitudes(even greater in near area),the more energy the rock mass releases and more seriously it would destruct.With the same amplitude level,the higher the self-potential frequencies( even higher in near area),the more frequently the rock mass fractures and more serious it would destruct.The more the points with different self-potential phases(in near area would be different while in far area would be same),the more fracture points in the rock mass and more seriously it would destruct.The in-depth disclosure of the natural electric field response mechanism to engineering rock mass destruction must be constrained by specific engineering scenarios and depend on the in-depth multidisciplinary cross-discipline research,improvement of simulation level and testing technology,employment of nonlinear signal analysis methods,etc.The construction of parallel detection and multi-parameter feature fusion of the self-potential method,the direct current resistivity methods and the induced polarization methods is expected to provide new geoelectrical theory in order to support the intelligence,accurate detection of disaster sources as well as disaster warning.