Using Nuclear magnetic resonance sounding to characterise groundwater distribution in Yangjiashan landslide, China

Abstract:

Geophysical methods has been widely used in landslide investigation to determine the geometric parameters of landslide structure, geotechnical composition, distribution and activity characteristics of groundwater in landslides. In particular, the commonly used ERT method can infer the water saturation and porosity information of rock and soil in the landslide body by observing the resistivity change of the medium. However, the conductivity of soil (especially clay) is not only related to water saturation, but also to the surface conduction mechanism of clay. This presents a new challenge for ERT method to be applied in landslides with rich clay content. In recent years, the near surface geophysical method based on the newly developed nuclear magnetic resonance theory has made a breakthrough in groundwater information detection. By observing the relaxation process of hydrogen nuclei in groundwater, MRS method can effectively avoid the influence of clay indicating conduction mechanism on the detection results. At the same time, important hydrogeological parameters such as water content per unit volume and permeability coefficient can be obtained according to the initial amplitude and time constant of relaxation signal. However, few reports have been published on the application of MRS method in landslide investigation. In this paper, we applied MRS method to the investigation of Yangjiashan landslide in Enshi city, China. The investigation results showed that MRS method can provide the groundwater distribution information and permeability coefficient information in the landslide body, and the detection results of MRS method are consistent with the in-situ drilling information after comparison. This proves that MRS method has important application value and prospect in landslide investigation.