Landslide investigation in field. describe the procedure to find the shallow or large scale landslide in field. To understand Landslide you should walk through whole Landslide.

1. FIELD
INVESTIGATION OF
LANDSLIDE
Prepared by:
Saurav Poudel
Roll no: 11

2. INTRODUCTION
Field investigations for landslides involve gathering
information about the physical characteristics and behavior of
a landslide in order to understand its causes and potential
hazards.
The goal of a field investigation is to understand the cause and
mechanism of the landslide, assess the potential for future
movement, and identify any hazard or impacts to structures or
infrastructures.
A field investigation typically includes steps such as
reconnaissance, site mapping, data collection, analysis, and
report writing.

3. Scope of Site investigations
The scope of a site investigation for a landslide typically includes:
• Conducting a through field investigation to identify the location and extent of the
landslide.
• Collecting data on the geology, soil, and hydrology of the area.
• Conducting laboratory tests on soil and rock samples to determine their physical and
mechanical properties.
• Analyzing the collected data to identify the cause of the landslide, such as soil type,
groundwater conditions and slope stability.
• Developing recommendations for mitigating or managing the landslide, such as
stabilizing the slope or redirecting water flow.
• Prepare a detailed report of the finding and recommendations of the client.

4. Phases of site investigation
Preliminary Phase
• Includes the site visit,
information collection
and planning of a study
program.
General Phase
• Involves the collection of
data to understand and model
the landslide.
• The line of borings are put
through the center of the
landslide to;
• determine the geological
conditions,
• measure the depth of
slippage,
• measure groundwater levels
near the slip surface, and
• collect samples for
laboratory testing of
classification and strength.
Specific Phase
• To provide more details
of the subsurface
conditions.
• Special sampling.
• Additional groundwater
data.
• Extra borings to
complete the landslide
model.

5. Preliminary Site Investigation
Data Collection
Site Reconnaissance
Site Plan
Measuring height and distance from a baseline
Section through the landslide
Measuring height and distance on a slope
Global Positioning System
Photographs
Observations

6. Geological mapping
Conducting geomorphological mapping to understand the landform and geology of the
area
Conducting geotechnical mapping to identify soil types, rock formations and slope
stability
Conducting hydrological mapping to identify drainage patterns and water sources
Conducting geophysical surveys to identify subsurface features and potential hazards
Conducting remote sensing analysis to identify changes in land cover and vegetation
Conducting geochronological dating to determine the age of the landslide
Conducting hazard and risk assessments to identify potential threats and areas of
vulnerability
Preparing a detailed map and report of the findings, including recommendations for
management and mitigation.

7. Topography
The shape and elevation of land can provide important information
about the causes of a landslide, as well as the potential for future
landslide in the area.
Topographic features such as slope angle, aspect, and elevation can
give clues about the stability of the land and can help identify the areas
that are more susceptible to landslide.
The direction of slope, or aspect, can also be important as it can
indicate the direction of water flow, which can help identify areas
where water saturation may be causing instability.
Topography study is done using various techniques such as GPS,
Aerial Photography, LIDAR or Total Station Surveys.

8. Survey Monitoring
It during filed investigation of landslide involves overseeing the
collection of data and observation related to the landslide event.
This includes monitoring the survey tram as they gather
information on the location, size and extent of the landslide, as
well as any change caused by the event.
During the field investigation, the survey team may use a variety
of tools and techniques to gather data, such as GPS equipment,
total station, and drones.
The survey monitor should oversee the use of these tools to ensure
that they are being used correctly and that the data being collected
is accurate and reliable

9. Difficult Access
Many landslides occur on very difficult terrain at a time of inhospitable weather.
Talus and other steep soils at marginal stability present very difficult access for
drilling rigs because even small temporary cuts may become locally unstable.
Inclinometer probes can be used in the steep soil slopes.
Flatter slopes with difficulty access, a drill crew can dig out a small level area to
erect a drilling platform on scaffolding.
Overwater drilling is used to drilling over water typically cost 3 to 4 times the cost
of drilling on land for the same amount of footage.

10. Overburden drilling
Hollow Stem Auger
Rotary Drilling with Mud
Overburden drilling
Power Auger
Odex method, Down the Hole Hammer
Wireline Drilling with casing Advancer
Shell and Auger(Cable Tool)

11. Standard Penetration Test
This test is the most common used in-situ test, especially for cohesion less soil
which cannot be easily sampled.
The test is extremely useful for determining the relative density and angle of
shearing resistance of cohesion less soils.
It can also determine the unconfined compressive strength of cohesive soils.
SPT Procedures:
1) The bore hole is to be drilled up to the desired depth.
2) The drilling tools are removed, and sampler is lowered to the bottom of the hole.
3) Three markings @150 mm are made on the rod of sampler.

12. 4) The sampler is driven into the soil by drop hammer
falling through the height of 762 mm @30
blows/min.
5) The number of blows required to drive each 150mm
of the sampler is counted.
6) The number of blows recorded for the first 150mm
is disregarded.
7) The number of blows recorded for the last two
150mm intervals are added to give the standard
penetration number.
8) Likewise, another samples of soil are collected at the
interval of 1.67m or where the soil profile or strata
changes.

13. The many different types of SPT hammer in use around the world may
conveniently be divided into the following categories:
1) Automatic trip hammers
Automatic trip hammers, which are standard in the UK, are also used in
Israel, Australia and Japan. This is the best type of hammer, because the
energy delivered per blow is consistent. Clayton (1990) reports tests on a
Dando automatic trip hammer which gave an average energy of 73% of the
free-fall energy, with a standard deviation of only 2.8%.
2)Hand-controlled trip hammers
Hand-controlled trip hammers are not widely used. An example is given in
Ireland, Moretto and Vargas (1970). The weight is lifted by hoist to what is
judged to be the correct height, and then tripped to give a free fall.
Inconsistencies can occur if the driller is careless in assessing how high to
lift the weight.

14. 3) Slip-rope hammers
Slip-rope hammers are widely used over much of the
world, including the USA, Japan, and South America.
Common types of slip-rope hammer are shown in fig
below.
The weight is lifted by a rope which passes over a sheave
on the top of the mast of the drilling rig and is pulled via a
cathead.
4) The cone penetration test (CPT) :
 The cone test is considered very useful determining the
bearing capacity of the pits sin cohesion less soils,
particularly in fine sand of varying density.

15. Relatively Undisturbed Sampling
Undisturbed sampling is used in field investigation of landslide to collect soil samples
without altering the natural state of the soil or the structure of the slope.
Techniques such as hand augering, soil coring, or push tube sampling are used for
undisturbed sampling.
The goal of undisturbed sampling is to obtain a representative sample of the soil
conditions and characteristics at the site.
The information can be used to better understand the cause and potential hazard
associated with the landslide.
The undisturbed samples will help to identify the soil properties and soil structure that
are related to the landslide and help to understand the mechanism of the landslide.

16. Test Pits, Trenches, Shafts and Adits
Test pits are small excavations used to examine soil and rock layers at a specific
location.
Trenches are longer and deeper excavations used to examine a larger area.
Shafts are deep vertical excavations used to study subsurface geology and collect
soil and rock samples.
Adits are horizontal excavations used to access underground mines or study
subsurface.
These methods can provide valuable information for understanding the cause of
landslide and developing mitigation strategies.

17. Geophysical Explorations

18. Geophysical techniques, such as ground-penetrating radar (GPR) and electrical
resistivity imaging (ERI), can be used to map subsurface geology and identify
potential failure planes or areas of weakness in the soil that may contribute to
landslides.
Techniques such as electrical resistivity tomography (ERT) and self potential
(SP) can be used to detect the presence of ground water and to identify areas of
high-water saturation that may contribute to landslides.
Geophysical methods such as magnetic and gravity surveys can be used to
identify areas of high rock densities or low porosity.
Geophysical techniques such as LiDAR and photogrammetry can be used to
estimate the volume of a landslide and to monitor any changes in the volume
over time, which can help to identify the areas of active movement and assess
the stability of the slopes.

19. Field Vane test
The field vane test is a form of direct shear test that is used to measure the shear
strength of soil in the field.
A vane is pushed into the soil at a certain depth, and force required to rotate the
vane is measured. This measurement can used to calculate the shear strength of the
soil.
The test can be conducted at different depths to measure the shear strength profile
of the soil, which help to identify areas of weakness or failure planes that may
contribute to landslides.
Field vane test can be used to measure the shear strength of soil in situ, which can
help to provide more accurate result than laboratory.
Field vane tests are particularly useful for investigating landslide on steep slopes,
as they can be conducted at the slope face, providing the best possible
representation of the soil conditions at the locations.

20. Conclusions
Field investigations are crucial for understanding the causes and
mechanism of landslides, as well as for assessing the stability of
slopes and identifying areas of high susceptibility.
A variety of techniques, such as geophysical methods, in-situ tests,
and remote sensing techniques, can be used in field investigation to
gather information about subsurface geology, soil properties, and
slope Stability.
Results from field investigations can be used to develop landslide
hazard and risk assessments, ass well as to inform the design of
mitigation and stabilization.
It is important to note that field investigations should be conducted
by a qualified geotechnical engineer or geologist with experience in
landslide investigation.

21. THANK YOU!