Basic concepts of Engineering geology from various books and internet images, which will be helpfull to many civil, petroleum and mining engineering students at basic level.

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(UNIT-IV)
P Shiva Kumar
Sr. Assistant Professor
Department of Civil Engineering

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Unit-3 Outcomes
At the end of the Course, Student will be able to:
CO 1 : Illustrate the Outcrop, Strike and Dip.
CO 2 : Illustrate the types and mechanism of folding.
CO 3 : Illustrate the types and mechanism of faulting.
CO 4 : Illustrate the joints and unconformities.
CO 5 : Understand the importance of structural
geology and stratigraphy for civil engineers.
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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE

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Contents
Structural Geology
• Strike, Dip and Outcrop.
• Study of common geological structures associating with the
rocks such as Folds.
• Faults.
• Joints and Unconformities- parts, types.
• Mechanism and their importance in Civil Engineering.
• Engineering properties of rocks.
Stratigraphy
• Introduction & Formations in India.
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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
Module 2 : Landslides, types and how do they occur
Module 2 : Landslides, types and how do they occur

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Landslides
P. Shiva Kumar
Sr. Assistant Professor
Department of Civil Engineering

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Learning Outcomes
At the end of this lecture, Student will be able to:
LO 1 : Understand the occurrence and types of
landslides.
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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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• Landslide(s) is a self explanatory term and phenomena, which is sliding of massive portion of
soil cover on the hill and mountain slopes due to geo-tectonical (diastrophic), intrusion of
groundwater ( high fluctuation – effluence) into soil, heavy rain fall and human involuntary
disturbances.
• Landslides are classified under mass movements or mass wasting or earth movements.
• Landslides can occur in offshore, coastal and onshore environments.
• Although the action of gravity is the primary driving force for a landslide to occur, there are other
contributing factors affecting the original slope stability.
• Causes include :
• Heavy rains, Floods and Ground water fluctuations
• Earthquakes
• Volcano eruptions
• Rapid snow melt
• Quarrying

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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ORIGIN OF LANDSLIDE
A) Extensive Rainfall :
• The most prominent landslide trigger is prolonged and heavy intensity rainfall.
• A universal landslide survey held in 2003 revealed that 90% of the landslides that occurred
were activated by a heavy rainfall.
• this is due to the enhancement of the pore water pressures in the soil.
B) Melting of Snow
• In several cold mountain places, snowmelt is frequent and may be a vital process for the
occurrence of landslides.
• This consequence is particularly significant when the warm weather is supplemented by
precipitation that adds to the groundwater and increases the melt rate.

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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C) Rivers:
• Rivers can damage the slopes, particularly during the floods that trigger a landslide.
D) Change in Water Level:
• Fast changes in the ground water level along a slope may trigger landslides.
E) Seismic Shaking:
• Earthquake waves through the rocks and earth create accelerations that alter the gravitational
forces on the slope.
• These processes are significant in the hilly areas where the seismic waves cause an increase in
the ground accelerations (topographic amplification).

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Landslide classification
The landslide classification based on Varnes' (1978)system has two terms:
A) The first term describes the material type - Rock, Earth, Soil, Mud and Debris
B) The second term describes the type of movement.
The five kinematically distinct types of movement are described in the sequence: -
Fall, Topple (overbalance ), Slide, Spread, Flow.
• Combining the two terms gives classifications such as:
• Rock fall,
• Rock topple,
• Debris slide,
• Debris flow,
• Earth slide,
• Earth spread, etc.

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Earth movements
A) Solifluction
B) Creep
C) Rapid Flow
A) Debris slides and slump
B) Rock slides
C) Rock fall
A) Due to Plastic outflow
B) Due to Compaction
C) Due to collapse
Earth Flow Landslide Subsidence

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Solifluction Floods or rapid flows

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Creep

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P Shiva Kumar, Sr. Assistant Professor, CE
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P Shiva Kumar, Sr. Assistant Professor, CE
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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Debris slide and slump Rock slide

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Rock fall from cliffs and razor
ridges

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Subsidence

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Types of landslides based on movement

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E) Lateral spreading: occurs
when the soil mass spreads
laterally and this spreading
comes with tensional cracks in
the soil.
F) Debris Flow: occurs down
slope movement of collapsed,
unconsolidated material
typically along a stream
channel.

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Causes of Landslides are classified as immediate cause and internal causes.
1. Immediate causes are seismic vibrations triggered from earthquakes, volcanic eruption, Tsunami and
landslide themselves.
2. Internal causes are factors that are influencing the portion of land to slide when the immediate
cause is triggered.
They are:
• Effect of slope
• Effect of water
• Effect of lithology
• Effect of associated structures
• Effect of human factors
• Effect of gravity

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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• Effect of water

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Engineering Geology
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• Effect of associated structures

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Effects of landslides
From the civil engineering point of view, if landslide occur at vulnerable places, they
may cause:
• Disruption of transportation or blocking of communications by damaging roads and
railways and telecommunication poles.
• Obstruction to the river flow in valleys, leading to their overflow and floods
• Damage to sewer and other pipelines
• Burial or destruction of buildings and other constructions
• It may also cause earthquakes.

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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Preventive measure of landslides
1. To counter the effect of slope
2. To counter the effect of water
3. To counter the structural defects
4. Not to reduce the stability of existing slopes
5. To counter the loose nature of overburden
6. Avoiding heavy traffic and blasting operations.

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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After completion of module 2 the student is now able to understand the
occurrence and types of landslides.
Summary

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Engineering Geology
P Shiva Kumar, Sr. Assistant Professor, CE
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