Insights into moisture-driven landslides using electrical and seismic methods
: case studies from Hollin Hill, UK and Thungsong, Thailand

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

The reduction of shear strength and landslide slope failure is directly associated with elevated soil moisture content and pore water pressures in the subsurface, particularly during heavy rainfall. The aim of this thesis is to investigate the use geophysical methods to study moisture-related landslides at two deferent sites. The first field site is a slow moving landslip located at Hollin Hill, UK. Self-potential (SP) measurements are used to characterise and monitor groundwater movement related to landslide reactivation in this site. The SP results show a strong relationship with rainfall, water levels and soil moisture content in the subsurface with correlation coefficients of approximately 0.91. Furthermore, the SP results reveal the pattern of fluid flow and characterise regions of negative and positive charges related to percolation and storage of ground water in the subsurface. In particular, before landslide reactivation, the main scarp (the top of the slope) reveals significantly negative SP value (less than -15 mV), due to water infiltration. In future work, the SP method could become a more commonly used technique for monitoring groundwater conditions as it provides important information precursory to landslides. The second field site is a shallow landslide located at Thungsong, in southern Thailand. Electrical resistivity tomography (ERT) and P-wave seismic refraction tomography (SRT) are applied to characterize internal structure and to study deformation mechanisms along 4 profiles. The integrated results of the SRT and ERT are used to produce a conceptual ground model, which delineates the remarkable contrast between the displaced material and the underlying bedrock. This model delineates zones of relatively low seismic velocity (less than 900 m/s) and low resistivity (less than 300 Ωm), which reveal high amounts of clay in the colluvium on the relatively steep slopes.
Date of Award28 Sep 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorJames M Wookey (Supervisor) & Juliet J Biggs (Supervisor)

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