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“Rainfall-induced Landslides: Investigation of Structure & Hydraulic Processes”
1 2 1 1Andrew Merritt , Jonathan Chambers , William Murphy & Jared West 1School of Earth & Environment, Earth Surface Science Institute, University of Leeds; 2Geophysical Tomography & Transportation Geotechnics, British Geological Survey
Introduction
Conventional Landslide Monitoring
The need to develop geophysical imaging techniques which are capable of not [1], [2]only characterising subsurface geological structure but also of informing
about processes taking place in the subsurface are an essential step towards understanding the trigger mechanisms responsible for landslide activation and subsequent movement.The main aim of this presentation is to present the results of a conventional landslide monitoring investigation, plus, preliminary results of a landslide geophysical monitoring campaign using Electrical Resistivity Tomography.
Electrical resistivity tomography (ERT) is a geoelectrical geophysical method which is sensitive to subsurface lithology changes and structure, as well as
[4] [5]subsurface moisture saturation . Due to the sensitivity of ERT it is particularly appropriate for monitoring rainfall-induced landsliding as it has the potential to
[6]monitor subsurface hydraulic changes associated with slope failure .
Fig.3. Plot of Peg Movement by RTK-GPS , showing movement along geophysical survey lines (See fig.1 & 2).
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g M
ov
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t (m
)
Date (DD/MM/YYYY)
Fig.2. Peg Number(x-direction perpendicular to survey line, y-direction parallel to survey line
The Landslide at Hollin Hill is investigated by several means, including:
Fig.4. Effective Rainfall & Piezometry Plot at Hollin Hill
Eff
ecti
ve D
ail
y R
ain
fall
(m
m)
Pie
zom
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evel
(m)
Date (DD/MM/YYYY)
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Abstract
Fig.1. Aerial Image of Hollin Hill Research Site.
Geoelectrical Monitoring of Landslides
Fig.5. Tiltmeter Results from 2009 Fig.6.Interpreted Stratigraphy of Hollin Hill Landslide System
Borehole 1 Borehole 5 Borehole 7
References
The study area is located at Low Mowthorpe, 12 miles west of the North Yorkshire town of Malton. Geographically, the study area is located within a south-facing Lias Group escarpment and is bound to the south by a broad topographic embayment (Fig.1).
Z-a
xis
(m)
X-axis (m)
Results of ERT Survey
Fig.9. (left) Interpreted profile of an ERT survey o f t h e H o l l i n H i l l Landslide System.
FlowSlumping
Fig.8. (below) Two volumetric images of resistivity distribution from Hollin Hill.
Fig.10. Photograph of an active flow deposit from Hollin Hill Landslide System.
North South
Peg Movement by GPS
Rainfall & Piezometric Level
Borehole Tiltmeter Intrusive Investigation - Drilling Campaign
N
N
This poster presents the results to date of a landslide monitoring campaign featuring both geophysical and conventional monitoring methods. The landslide system is within Lias group formations of the Lower Jurassic. The landslide is monitored using a three-dimensional geophysical method, affording the ability to observe a three-dimensional subsurface geological structure in its entirety. This is as opposed to discrete sampling or two-dimensional geophysical methods, which do not permit volumetric observations.
Geological Model
Research Site
[2] FRIEDEL, S., THIELEN, A. & SPRINGMAN, S. M. 2006. Investigation of a slope endangered by rainfall-induced landslides using 3D resistivity tomography and geotechnical testing. Journal of Applied Geophysics 100-114.
[3] JONGMANS, D. & GARAMBOIS, S. 2007. Geophysical investigation of landslides : a review. Bull. Soc. géol. Fr. , 178, 101-112.
[1] PERRONE, A., IANNUZZI, A., LAPENNA, V., LORENZO, P., PISCITELLI, S., RIZZO, E. & SDAO, F. 2004. High-resolution electrical imaging of the Varco d'Izzo earthflow (southern Italy). Journal of Applied Geophysics, 17-29.
[4] CHAMBERS, J. E., GUNN, D. A., MELDRUM, P. I., WILKINSON, P. B., OGILVY, R. D., HASLAM, E., HOLYOAKE, S. & WRAGG, J. 2011a. Volumetric imaging of earth embankment internal structure and moisture movement as a tool for condition monitoring. Railway Engineering 2009, 11th International Conference and Exhibition, University of Westminster, London, UK, 29th-30th June.
[5] CHAMBERS, J. E., MELDRUM, P. I., GUNN, D. A., WILKINSON, P. B., MERRITT, A., MURPHY, W., WEST, L. J., KURAS, O., HASLAM, E., HOBBS, P., PENNINGTON, C. & MUNRO, C. Year. Geophysical-geotechnical sensor networks for landslide monitoring. In: The Second World Landslide Forum, 3-7 October 2011b Rome.
Staithes Sandstone Formation
Whitby Mudstone Formation
DoggerFormation
Redcar MudstoneFormation
North South
Mainscarp
Minorscarp
Ancient Flow Deposits
Recent Flow Deposits
Failure Surface
BH7 BH5Topsoil0.0
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Agricultural soil0.13
Flow deposits
0.670.921.05
1.56
2.983.05
4.15
5.20
5.80
Slump deposits
SSF in-situ
De
pth
(m
)
LevelmOD
Lab Trough Samples
Topsoil0.30
0.82Agricultural soilClay
1.20
2.10
2.70
Flow deposits
3.65
4.21
Slump deposits
Depth(m)
5.07
6.66
7.00
SSF in-situ
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
79.22
78.22
77.22
76.22
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74.22
73.22
72.22
De
pth
(m
)
LevelmOD
Depth(m)
Fig.7.Geological Model of Hollin Hill research site.
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