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Analysis of Geotechnical-Assisted 2-D Electrical Resistivity Tomography Monitoring of Slope Instability in Residual Soil of Weathered Granitic Basement
Frontiers in Earth Science ( IF 2.9 ) Pub Date : 2020-09-23 , DOI: 10.3389/feart.2020.580230
Oladunjoye P. Olabode , Lim H. San , Muhd H. Ramli

Prolong heavy rainfall is increasingly inducing slope instabilities on the high-risk hills of weathered granitic basement in Penang. These slope instabilities are spatially controlled with changes in geotechnical properties of the slope soils. A reliable method to include density as part of geotechnical properties to calibrate electrical resistivity tomography (ERT) resistivity distribution in slope instability monitoring is still rare. Hence, we present six ERT data that were acquired with a survey length of 60 m and 1.5 m electrode spacing using Wenner–Schlumberger array from 2019 to 2020. The results were calibrated with the laboratory-determined geotechnical properties: moisture content (MC), particle-size distribution, density, and hydraulic conductivity (HC). The result of the analysis of ERT models classified resistivity distribution into saturated zones of <600 Ωm with a high percentage of >20% silt and clay, weak zones of 600–3,000 Ωm, and basement rocks of >5,000 Ωm. The presence of floaters and boulders of resistivity >4,000 Ωm overlie saturated zones coupled with multiple rainfall events that act as triggering factors for slope instability and failure. Geotechnical results show strong correlation of R ≈ 0.94 between density and resistivity values which are crucial for the calibration of the ERT models because low-resistivity <600 Ωm areas have high MC, 30.1% with low density, 1,176 kg/m3, and HC, 2.02 × 10–5 m/s, whereas high resistivity <3,000 Ωm areas have lower MC, 11.4% with relatively high density 1,458 kg/m3, and HC, 1.34 × 10–2 m/s. Therefore, we conclude that low-resistivity areas are composed of earth materials that are less-dense low-permeable unstable zones of displacement which constitute subsurface drainage paths that are precursors to slope instability.



中文翻译:

岩土辅助二维电阻层析层析成像监测风化花岗岩基底残留土体边坡失稳的分析

长时间的强降雨越来越导致槟城风化花岗岩地下室的高风险山坡发生边坡失稳。这些边坡的不稳定性是通过边坡土力特性的变化在空间上控制的。在边坡失稳监测中,将密度作为岩土属性的一部分来校准电阻层析X射线照相术(ERT)电阻率分布的可靠方法仍然很少。因此,我们展示了从2019年到2020年使用Wenner–Schlumberger阵列以60 m的测量长度和1.5 m的电极间距采集的六个ERT数据。这些结果已通过实验室确定的岩土特性进行了校准:含水量(MC),粒度分布,密度和水力传导率(HC)。ERT模型的分析结果将电阻率分布划分为<600Ωm的饱和带,其中粉砂和粘土的百分比高于20%,薄弱的区域为600–3,000Ωm,基底岩层的密度大于5,000Ωm。电阻率大于4,000Ωm的漂浮物和巨石的存在覆盖了饱和区域,再加上多个降雨事件,这些降雨事件是斜坡失稳和破坏的触发因素。岩土工程结果表明,密度与电阻率值之间的R≈0.94有很强的相关性,这对于ERT模型的校准至关重要,因为低电阻率<600Ωm的区域具有较高的MC,低密度的为30.1%,低密度为1,176 kg / m 4,000Ωm覆盖饱和带,并伴有多次降雨事件,这些降雨事件是边坡失稳和破坏的触发因素。岩土工程结果表明,密度与电阻率值之间的R≈0.94有很强的相关性,这对于ERT模型的校准至关重要,因为低电阻率<600Ωm的区域具有较高的MC,低密度的为30.1%,低密度为1,176 kg / m 4,000Ωm位于饱和带上,并伴有多个降雨事件,这些降雨事件是边坡失稳和破坏的触发因素。岩土工程结果表明,密度与电阻率值之间的R≈0.94有很强的相关性,这对于ERT模型的校准至关重要,因为低电阻率<600Ωm的区域具有较高的MC,低密度的为30.1%,低密度为1,176 kg / m3和HC为2.02×10 –5  m / s,而高电阻率<3,000Ωm的区域则MC较低,为11.4%,密度相对较高,为1,458 kg / m 3,HC为1.34×10 –2  m / s。因此,我们得出的结论是,低电阻率地区由土质材料组成,这些土质材料是密度较低的低渗透不稳定位移区,构成地下排水路径,是斜坡失稳的先兆。

更新日期:2020-11-12
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