Landslides

1
Landslides Slope Stabilisation
2

• BGS367 LANDSLIDES SLOPE STABILITY

SCHOOL OF EARTH ENVIRONMENTAL SCIENCES Part 5
Landslides Slope Stabilisation
3
Overview

• Landslide slope monitoring
• Slope Stabilisation
• Drainage
• Mass Support
• Profile Modification
• Rock fall Measures
• Ground Improvement
• Ground Anchoring

4
Landslide Slope Monitoring
Slope Indicator www.slopeindicator.com/pdf/applic
ation20guide.pdf
5
Landslide Slope Monitoring
Grasse
6
Landslide Slope Monitoring
Landslide track sensor La Valette, Barcelonette
7
InSAR
C. Squarzonia et al (2003) Nine years of spatial
and temporal evolution of the La Valette
landslide observed by SAR interferometry.
Engineering Geology 68 5366
8
InSAR
Multitemporal interferometric series from July
1995 to April 1996.
Displacement vectors for the 1995 1996 data set
for each of the four mapped landslide zones
9
GPS
J.-P. Malet, O. Maquaire, E. Calais (2002) The
use of Global Positioning System techniques for
the continuous monitoring of landslides
application to the Super-Sauze earthflow
(Alpes-de-Haute-Provence, France). Geomorphology,
43, pp 33 54, www.elsevier.com/locate/geomorph
10
Aerial Photos
B. Casson, C. Delacourt, D. Baratoux, P. Allemand
(2003) Seventeen years of the La Clapiere
landslide evolution analysed from ortho-rectified
aerial photographs. Engineering Geology 68, pp
123 139. www.elsevier.com/locate/enggeo
11
Aerial Photos
Example of ortho-rectification of image 60 of
mission FP 3540-3840 (above Saint-Etienne-De-Tine
e (France) in 1991). (a) Image 60 in acquisition
geometry before ortho-rectification the scale
and the north direction are not represented on
this photograph because it has no sense on an
image in acquisition geometry. (b) Image 60 in
cartographic geometry after ortho-rectification
with the scale and the north direction the
control points used for the absolute orientation
of DEMs are figured (in white) on this image.
12
Aerial Photos
Ortho-rectified images used to study the
landslide evolution. They are presented with the
accuracy map of each DEM which points out the
high precision of the landslide region. (a) Image
of 1983 and its accuracy map. (b) Image of 1991
and its accuracy map. (c) Image of 1999 and its
accuracy map.
13
Aerial Photos
Landslide evolution Landslide boundaries and
scarp surfaces in 1983 Landslide boundaries and
scarp surfaces in 1991 Landslide boundaries and
scarp surfaces in 1999 Major faults Alluvial
fans Rivers Roads
14
Remote Sensing Techniques
SPOT satellite image of the Blackhawk Landslide,
California
Franco Mantovani, Robert Soeters and C. J. Van
Westen (1996) Remote sensing techniques for
landslide studies and hazard zonation in Europe.
Geomorphology, 15, pp 213 225.
Engineering Geology 68 (2003) Volume 68, Issues
1-2, Pages 1-139 Special issue from the symposium
on Remote Sensing and Monitoring of Landslides.
www.elsevier.com/locate/enggeo
15
Slope Stabilisation

• Slopes may be stabilised by one or more of the
  following
• Improving slope drainage
• Supporting or anchoring the existing profile
• Modifying slope profile

16
Drainage
17
Slope Landslide Drainage

18
Slope Landslide Drainage
Schematic diagram of subhorizontal and vertical
drains used to lower groundwater in natural
slopes. After Gedney Weber (1978) Design
Construction of Sol Slopes. In Landslides
Analysis Control Special Report 176. National
Research Council, Washington.
19
Drainage Surface Drains
Overstrand, Norfolk
20
Drainage Surface Drains
Overstrand, Norfolk
21
Drainage Surface Drains
Overstrand, Norfolk
22
Drainage Surface Drains
Overstrand, Norfolk
23
A46 Batheaston Bypass
24
A46 Batheaston Bypass
25
A46 Batheaston Bypass
26
A46 Batheaston Bypass
27
A46 Batheaston Bypass
28
A46 Batheaston Bypass
29
A46 Batheaston Bypass
30
Drainage Surface Deep Drains
Nr Blaina, Ebbw Fawr Valley
East Pentwyn
31
East Pentwyn
32
East Pentwyn
33
Deep Drains Interceptor Tunnels
East Pentwyn
34
Drainage Surface Shallow Drains
Cwmtillery
35
Drainage Surface Shallow Drains
Blaencwm
36
Drainage Slope Modification
Tyn-bedw
37
Drainage Deep Drains
Sinard
38
Electro - osmosis
If a DC electric potential is applied to a
saturated day soil, the cations will be attracted
to the cathode the anions will be attracted to
the anode. The cations anions will carry
their water of hydration with them as they move
move additional water by viscous drag. Due to the
net negative charge the net flow of pore water of
the clay particles, there are more mobile cations
than anions, so will be toward the cathode. If
the cathode is a wellpoint, the water collected
at the cathode can be removed the soil between
the electrodes will consolidate. Consolidation
will be greatest at the anode least near the
cathode. No consolidation will occur at the
cathode itself. The process of electroosmosis
will result in a lower moisture content, lower
compressibility increased strength. There may
be an additional increase in strength a
decrease in plasticity due to electrochemical
hardening, which occurs when the application of a
DC electric potential to a saturated clay causes
electrode corrosion ion exchange, mineral
alteration. US Army Corps of Engineers Technical
Letters Publication Number ETL 1110-1-185
Engineering and Design - Guidelines on Ground
Improvement for Structures and Facilities
http//www.usace.army.mil/publications/eng-tech-l
trs/etl1110-1-185/toc.htm
39
Electro - osmosis
C. J. Athmer B. E. Huntsman, A Case For
Electroosmosis Remediation Terran Corporation,
www.Terrancorp.Com/techdocs/ektri/ektri.Htm
40
Electro - osmosis
LasagnaTM is the integration of electroosmosis
with in-situ treatment designed to provide
uniform treatment of non-homogenous soils or clay
silt-laden soils. Electroosmosis is used to
move soil pore water contaminants to
treatment zones placed in the contaminated area.
USEPA www.epa.gov/region1/assistance/ceit_iti/tech
_cos/terla.html
41
Mass Support
42
Rock Slope Stabilisation

• Methods of stabilization fall into three
  categories
• Reinforcement - Rock removal - Protection

43
Mass Support Systems Retaining Walls
Tinee Valley
44
Mass Support Systems Dental Masonry
Barreme
45
Mass Support Systems Shotcrete
Barreme
46
Mass Support Systems Shotcrete
Barreme
47
Mass Support Systems Concrete Walls
Lamphrey
48
Mass Support Systems Gabion Walls
Blaencwm
49
Profile Modification Hanging Blocks
Tinee Valley
50
Profile Modification Hanging Blocks
Tinee Valley
51
Profile Modification Berm Ledges
Tinee Valley
52
Profile Modification Berm Ledges
Delabole
53
Profile Modification Berm Ledges
Ubaye Valley
54
Profile Modification Slope Regrading
Aberfan
55
Profile / Mass Support Toe Weight
Overstrand, Norfolk
56
Folkestone Warren, Kent
57
Profile Modification Erosion Control
St Andres les Alpes
58
Rock Fall Measures
59
Rock Fall Measures Earth Bank
Barreme
60
Rock Fall Measures Earth Bank
Barreme, France
61
Rock Fall Measures Shelters
Montenyard
62
Rock Fall Measures Shelters
Montenyard
63
Rock Fall Measures Rock Catch Nets
Barreme
64
Rock Fall Measures Rock Catch Nets
Barreme
65
Rock Fall Measures Rock Catch Nets
Geobrugg Rockfall Test http//www.geobrugg.com/sit
e/geobrugg.lasso?typArtikelcategory200_Rockfall
subcategoryLandSpracheen-gb1id35637
66
Rock Fall Measures Predictive Models

• Trajectory Prediction
• RockfallTM
• Rock fall simulation analysis for catchment
  design
• RocFall Demo\RocFall.exe

An effective method of minimizing the hazard of
rock falls is to let the falls occur to control
their distance direction of travel.
67
Rock Slope Reinforcement
The common feature of most rock reinforcement
techniques is that they minimize the relaxation
and loosening of the rock mass that may take
place as a result of excavation, unloading or
natural triggering mechanisms.
68
Ground Anchoring Rockbolts Netting
Foel Goch
69
Ground Anchoring Rockbolts Netting
Foel Goch
70
Ground Anchoring Rockbolts Netting
Tinee Valley
71
Ground Anchoring Rockbolts Netting
Tinee Valley
72
Ground Anchoring Rockbolts Netting
Tinee Valley
73
Ground Anchoring Rock Anchors
Foel Goch
74
Ground Anchoring Rock Anchors
Foel Goch
75
Ground Anchoring
Getting Remedial Works Wrong In this case, a
failure to allow for movements on a deeper
possible slide surface - one that is not exposed
by the works. Differential movements in the
slide mass wrenched off some anchor heads because
of the grillage details.
Bromhead, E. (2000) Landslides and how to treat
them. ISL, Cardiff
76
Ground Anchoring
Taiwan
77
Ground Improvement Vegetation
Broadway
78
Ground Improvement Geotextiles
A2 M2 Widening
79
Ground Improvement Liming
Lime-Cement Stabilization of Slopes - Experiences
and a Design Approach www.geotek.sintef.no/LimeCem
ent.htm
80
Ground Improvement Liming
Schematic cross-section illustrating process of
lime-slurry pressure injection of embankment
slope (Boynton Blacklock, 1985).
81
Ground Anchoring Soil Nails
82
Ground Anchoring Soil Nails
83
Ground Anchoring Soil Nails
A2 M2 Widening
84
A2 M2 Widening
85
A2 M2 Widening
86
Ground Improvement Reinforced Earth
87
A2 M2 Widening
88
Ground Improvement Reinforced Earth
89
Lamphrey Ramp, France
90
Ground Improvement Vegetation

• Vegetation contributes to slope stability
  through root reinforcement rainfall
  interception evapotranspiration, which
  reduces pore pressures

Biotechnical Stabilisation
Classification of different biotechnical slope
protection and erosion control measures (Gray
Sotir, 1992).
91
Ground Improvement Vegetation
Grasse
92
Ground Improvement Vegetation
Grasse