自然电位法在滑坡监测中的应用研究

滑坡是最主要的地质灾害之一，其中降雨诱发型滑坡分布范围最广、造成的损失最大。降雨入渗会增加近地表岩土体的含水饱和度从而使其容重增大、抗剪强度下降，进而降低坡体稳定性。研究坡体雨水入渗及浅地表水的流动过程对滑坡的监测预警至关重要。基于动电机制下的双电层模型，降雨入渗过程中孔隙水的流动可产生自然电位（SP）响应。目前，自然电位方法已被用于环境监测、矿产勘探等领域，在滑坡监测中应用相对较少，国内相关研究尚不多见。因此，本研究基于室内控制试验，开展自然电位法在滑坡监测中的应用探索，旨在获取流体入渗过程中的自然电位响应，探讨自然电位响应与变饱和流动的定量关系，为基于自然电位数据反演地下流场打下基础。

   首先，我们建立了室内自然电位观测系统，通过试验发现市面已有的测量电极在室内小尺度试验中存在显著的尺度效应，严重影响试验结果。为此，本文研制了一种适用于短期室内模拟试验的微型铅-氯化铅固体不极化电极。利用3D打印技术快速制备复杂结构、高精度微型电极壳体；在电解质制备中添加亲水性强和离子传导性高的纳米级气相二氧化硅，提升电极的稳定性。电极性能测试结果显示，自制的微型铅系固体不极化电极具有尺寸小、温度系数低、电极电位稳定性好及自噪音与市面上体积大的电极相当等特点，达到了室内模拟试验的要求。

然后，基于开发的微型不极化电极，开展了室内一维渗流试验和二维滑坡控制试验。试验结果表明，自然电位对流体流动敏感，可准确反映流体的一维变饱和渗流过程。通过对观测数据的定量分析，标定了饱和状态下的动电耦合系数，推导了基于动电耦合过程的达西流速和基于孔隙渗流过程的达西流速，发现两者具有较好一致性。上述结果表明自然电位观测能够定量地反映一维渗流流速的大小，揭示了自然电位响应与变饱和流动的定量关系。二维滑坡试验中，在砂土没有完全饱和时自然电位能反映水的流动方向和水分汇集区域，可在一定程度上反映非饱和土体的渗流过程。

   综上，本研究开发小型室内滑坡控制试验平台，研制了适用于室内模拟试验的新型微型铅系固体不极化电极，开展了降水入渗滑坡试验。通过入渗过程中岩土内的高密度自然电位、孔隙压力、温湿度等物理量的同步观测，获取了流体入渗过程中的自然电位响应，建立了一维渗流过程中自然电位场与流场的定量关系，为自然电位法在滑坡监测中的应用提供基础。

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