ENGINEERING GEOLOGY

ENGINEERING GEOLOGY
(ACE003)
B.Tech II YEAR I SEM
Prepared By:
Mr. K Tarun kumar
Asst. Professor
Department of Civil Engineering

Definition:-
• The science which deals with the physical
structure and substance of the earth, their
history, and the processes which act onthem.
• The geological features of adistrict.
• The geological features of a planetarybody.
Geology Earthscience
Geo
logous

The importance of geology in civil engineering may
briefly as follows:
• Geology provides a systematic knowledge of construction
material, its occurrence, composition, durability and other
properties. Example of such construction materialsisbuilding
stones, road metal, clay, limestones andlaterite.

• The knowledge of the geological work of natural agencies
such as water, wind, ice and earthquakes helps in planningand
carrying out major civil engineering works. For example the
knowledge of erosion, transportation and deposition helps
greatly in solving the expensive problems of river control,
coastal and soilconservation.

• Ground water is the water which occurs inthe
subsurface rocks. The knowledge about its
quantity and depth of occurrence is required in
connection with water supply, irrigation,
excavation and many other civil engineering
works.

• The foundation problems of dams, bridges and buildings are
directly concerned with the geology of the area where they are
to be built. In these works drilling is commonly undertaken to
explore the ground conditions. Geology helps greatly in
interpreting the drillingdata.
• In tunneling, constructing roads, canals, docks and in
determining the stability of cuts and slopes, the knowledge
about the nature and structure of rocks is verynecessary.
• Before staring a major engineering project at a place, a
detailed geological report which is accompanied by geological
maps and sections, is prepared. Such a report helps in planning
and constructing theprojects.

Physical Geology:
• Physical Geology uses the scientific method to
explain natural aspects of the Earth - forexample,
how mountains form or why oil resources are
concentrated in some rocks and not inothers.
• This chapter briefly explains how and why Earth's
surface, and its interior, are constantly changing. It
relates this constant change to the majorgeological
topics of interaction of the atmosphere, water and
rock.

Petrology:-
• Petrology is the branch of geology that studiesthe
origin, composition, distribution and structure
of rocks.
• (from the Greek language : petra-"rock" andlogos-
"study")
• “Lithology” was once approximately synonymous
with petrography, but in current usage, lithology
focuses on macroscopic hand-sample or outcrop-scale
description of rocks while petrography is thespecialty
that deals with microscopicdetails.

Branches:
• There are three branches of petrology,corresponding
to the three types of rocks:
Igneous, metamorphic, and sedimentary.
• Igneous petrology focuses on the compositionand
texture of igneous rocks (rocks such
as granite or basalt which have crystallized from
molten rock or magma). Igneous rocks
include volcanic and plutonic rocks.

• Sedimentary petrology focuses on the compositionand
texture of sedimentary rocks (rocks such
as sandstone, shale, or limestone which consist of
pieces or particles derived from other rocks or
biological or chemical deposits, and are usually bound
together in a matrix of finer material)

• Metamorphic petrology focuses on the composition and
texture of metamorphic rocks (rocks such as slate,
marble, gneiss, or schist which started out as
sedimentary or igneous rocks but which have undergone
chemical, mineralogical or textural changes due to
extremes of pressure, temperature orboth).
• Metamorphic rocks arise from the transformation of
existing rock types, in a process called metamorphism,
which means "change in form". The original rock
(protolith) is subjected to heat (temperatures greater
than150to 200°C) causing
profoundphysicaland/orchemicalchange.

Structural geology:
• Structural geology is the study of the three-
dimensional distribution of rock units with respect to
their deformationalhistories.
• The primary goal of structural geology is to use
measurements of present-day rock geometries to
uncover information about the history of deformation
(strain) in the rocks, and ultimately, to understand the
stress field that resulted in the observed strain and
geometries.

Weathering of Rocks:
• Weathering breaks down and loosens the surface minerals
of rock so they can be transported away by agents oferosion
such as water, wind andice.
• There are two types of weathering: mechanical and
chemical.
• Mechanical or physical weathering involves the breakdown
of rocks and soils through direct contact with atmospheric
conditions, such as heat, water, ice andpressure.
• The second classification, chemical weathering involves the
direct effect of atmospheric chemicals or biologically
produced chemicals also known as biological weathering in
the breakdown of rocks, soils andminerals.

Excavation:
• The section reviews standard excavation
practices
slopes
used to construct and
and provides current
modify rock
design and
construction guidelines for theiruse.
• The most commonare
1.Blasting (which includes drilling the holes to be
filled withexplosives)
2. Ripping
3. Drilling

• Blasting—the contr1olle.BdLusAeSofTeIxNploGsiv:es to excavate rock—has
been part of construction engineering for hundreds ofyears.
will• In any blasting situation, the geologic structure of the rock mass
be the most important consideration.
• It is practiced most often in mining, quarrying and civil engineering
such as dam or road construction. The result of rock blasting is often
known as a rockcut.
• Blasting is used for rock excavation on both small- andlarge-scale
projects. There are two generaltypes:
1. productionblasting
2. Controlledblasting.

2. RIPPING:
• Uses a tractor with an attached tooth or teeth that is lowered
into the rock and dragged to break up material forexcavation.
• The tooth of the ripper can leave scars on the rock surface. The
tractor cannot be used on steep slopes because of risk of
overturning. Ripping is limited to relatively low densityrocks.

3. DRILLING:
• Blast holes are drilled at various orientations,fromvertical
throughhorizontal.
• To create vertical holes, which are used almost exclusivelyin
production blasting, rock slope excavation uses two types of
drilling:
1. Downhole
2. Step drilling
• Horizontal drilling is used for both production and controlled
blasting because of limited drill rig access or geometry
requirements.
• Angled drilling can be performed as determined by slope face
anglerequirements.

• The modes of failure can be groupedinto
four primarymechanisms:
1.Planar Failure (A)
2.Wedge Failure (B)
3.Circular Failure (C)
4.Toppling Failure(D)

STRATIGRAPHY:
• Stratigraphy is a branch of geology which studiesrock
layers (strata) and layering(stratification).
• It is primarily used in the study of sedimentaryand
layered volcanicrocks.
• Stratigraphy includes two relatedsubfields:
1. Lithologic stratigraphy orlithostratigraphy,
2. Biologic stratigraphy orbiostratigraphy.

• Application of stratigraphy was by William Smith in the
1790s and early 1800s. Smith, known as the "Father of
Englishgeology“.

1) Lithostratigraphy:
Lithostratigraphy is the geological scienceassociated
with the study of strata or rock layers.
Litho logy:
The litho logy of a rock unit is a description of its
physical characteristics visible at outcrop, in hand or core
samples or with low magnification microscopy, such as
color, texture, grain size, or composition.

Strata:
Strata are layers of rock, or sometimes soil.
Innature, strata come in many layers. It is a
term in sedimentary and historical geology; the
singular is stratum. These layers are laid down
as sediment, often in the sea, and are slowly
changed by pressure, heat and chemical action
into rocks.

2) Biostratigraphy:
• Bio stratigraphy is the branch of stratigraphy which
focuses on correlating and assigning relative ages of rock
strata by using the fossil assemblages contained within
them.
• Biologic stratigraphy was based on William
principle of faunal succession, which predated,
Smith's
and was
evidence for,one of the first and most powerful lines of
biologicalevolution.

DEFINITION:
• Paleontology is the study of what fossils tell us aboutthe
ecologies of the past, about evolution, and about our
place, as humans, in theworld.
• Paleontology incorporates knowledge from biology,
geology, ecology, anthropology, archaeology, andeven
computer science to understand the processes that have
led to the origination and eventual destruction of the
different types of organisms since lifearose.

• It includes the study of fossils to determine
organisms' evolution and interactions with eachother
and theirenvironments.
• The simplest definition is "the study of ancientlife”.
• Paleontology seeks information about severalaspects
of past organisms: "their identity and origin, their
environment and evolution, and what they can tell us
about the Earth's organic and inorganicpast".

GEOLOGICAL TIME SCALE:
• The geological time scale (GTS) is a system of
chronological measurement that relates stratigraphy to
time, and is used by geologists, paleontologists, and
other Earth
relationships
scientists to describe the timing and
between events that have occurred
throughout Earth’shistory.

OUTCROP:
• An outcrop or rocky outcrop is a visible exposure of bedrock
or ancient superficial deposits on the surface of the Earth.
• However, in places where the overlying cover is removed
through erosion or tectonic uplift, the rock may be exposed, or
cropout.
• It may also exposed at the Earth's surface due to human
excavations such as quarrying and building of transportroutes.

STRIKE AND DIP:
• Strike and dip refer to the orientation or attitudeof
a geologic feature.
• The strike line of a bed, fault, or other planar feature, is aline
representing the intersection of that feature with a horizontal
plane.
• On a geologic map, this is represented with a shortstraight
line segment.
• Strike (or strike angle) can be given as either a quadrant
compass bearing of the strike line or in terms of east or westof
true north or south oriented parallel to the strikeline.

DIP:
• Thedipgivesthesteepestangleofdescentofatiltedbedor
feature relative to a horizontal plane.
• One technique is to always take the strike so the dip is 90°to
the right of thestrike.
• The angle of dip is generally included on a geologic map
without the degree sign.

FOLDS:
• Folds are one of the most common geological structuresfound
inrocks.
• When a set of horizontal layers are subjected tocompressive
forces, they bend either upwards or downwards.
orcurvedor
• The bends noticed in rocks are calledFolds.
• Folds are described variously as wavyor arch
warping appearances found inrocks.

Types of Folds:
Anticline:
• When the beds are bent upwards, the resulting fold iscalled
anticline. This folds is convex upwards.
Anti = Opposite
Cline= Inclination

Syncline:
• Syncline is just opposite to anticline in its nature, when thebeds
are bent downwards the resulting fold is called syncline.
• This fold is convexdownwards.

Symmetrical:
• When the axial plane divides a fold into two equal halves in such
a way that one half is the nature image of another, then such fold
is called Symmetricalfolds.

Asymmetrical:
• If the two halves are not mirror images, then the fold is called as
asymmetrical fold.
• If the compressive forces responsible for folding are not of the
same magnitude, asymmetrical folds areformed.

Open folds:
• Depending on the intensity of deformation, the beds of the
folds may or may not have uniform thickness.
• If the thickness of bed is uniform throughout the fold it is
called Openfold.

Closed Folds:
• In a fold if the beds are thinner in the limb portions andthicker
at crests and troughs, such fold is called a closed fold.

FAULTS:
or zoneoffractures betweentwo blocks of• A fault isafracture
rock.
• Faults allow the blocks to move relative to eachother.
• This movement may occur rapidly, in the form of an earthquake -
or may occur slowly, in the form ofcreep.
• Faults may range in length from a few millimeters to thousands of
kilometers.
• During an earthquake, the rock on one side of the faultsuddenly
slips with respect to the other.

CAUSES OF FAULTING:
• Faults mainly occur in regions of structuralinstability.
• It may be recollected that faults develop mainly due to shearor
sliding failures resulting from tensional, compression forces.
• When an earthquake occurs on one of these faults, the rock on
one side of the fault slips with respect to theother.

FAULT PLANE:
• This is the plane along which the adjacent blocks are relatively
displaced.
• In other words, this is the fracture surface on either side of
which the rocks had moved past oneanother.

FOOT WALL AND HANGING WALL:
• When the fault plane is inclined the block which liesbelowthe
fault plane is called “Foot wall”.
• And the other block which rests above the fault plane iscalled
“Hangingwall”.

SLIP:
• The displacement that occurs during faulting is called theslip.
• The total displacement is known as the netslip.
• This may be along the strike direction or the dipdirection.

EARTHQUAKES
DEFINITION:
A sudden violent shaking of the ground, typically causing great
destruction, as a result of movements within the earth's crust or
volcanic action.
A sudden release of energy in the earth's crust or upper mantle,
usually caused by movement along a fault plane or by volcanic
activity and resulting in the generation of seismic waves which
can be destructive.

Sesimic Waves:
Seismic waves are waves of energy that travel through
the Earth's layers, and are a result of an earthquake,
explosion, or a volcano that gives out low-frequency
acoustic energy.
Seismic waves are studied by geophysicists called
seismologists. Seismic wave fields are recorded by a
seismometer, hydrophone (in water), or accelerometer.ncy
acoustic energy.

•The propagation velocity of the waves depends on
density and elasticity of the medium.
• Velocity tends to increase with depth and ranges from
approximately 2 to 8 km/s in the Earth's crust, up to
13 km/s in the deep mantle.

Classification and causes of Earthquake:
Based on depth of their origin, earthquake are described as
shallow or intermediate or Deep.
•Earthquake with a focus depth less than 60km are called shallow
earthquake.
•If the depth more than 60km but less than 300km, they are called
Intermediate earthquake.
•Which have focus depth more than 300km, they are called Deep
earthquake.

Based on the causes responsible for their occurrence,
earthquakes are described as Tectonic or non Tectonic.
•Tectonic earthquake are exclusively due to internal
causes, due to disturbances or adjustments of geological
formations taking place in the earth’s interior, they are
les frequent, but more intensive and hence more
destructive in nature.
•The Non Tectonic earthquake on the other hand, are
generally due to external or surfacial causes. This type
of earthquake is very frequent, but minor in intensity
and generaly not destructive in nature.

Types:
Among the many types of seismic waves, one can
make a broad distinction between body waves and surface waves.
•Body waves travel through the interior of the Earth.
•Surface waves travel across the surface.
•Surface waves decay more slowly with distance than do body
waves, which travel in three dimensions.

Includes Primary and Secondary waves:
Primary waves(P-wave):
•Primary waves are compression waves that are
longitudinal in nature.
•P waves are pressure waves that travel faster than other
waves through the earth to arrive at seismograph stations
first, hence the name "Primary".
•These waves can travel through any type of material,
including fluids, and can travel at nearly twice the speed
of S waves.
•In air, they take the form of sound waves, hence they
travel at the speed of sound.
•Typical speeds are 330 m/s in air, 1450 m/s in water and
about 5000 m/s in granite.

Secondary waves(S-Waves):
•Secondary waves (S-waves) are shear waves that are transverse in
nature.
•Following an earthquake event, S-waves arrive at seismograph
stations after the faster-moving P-waves.
•S-waves can travel only through solids, as fluids (liquids and
gases) do not support shear stresses.
• S-waves are slower than P-waves, and speeds are typically around
60% of that of P-waves in any given material.

Definition:
•An Earthquake is a sudden and rapid shaking of the ground due to
passage of vibrations beneath caused by transient disturbance of
elastic or gravitational equilibrium of rocks.
•The scientific study of earthquakes is called Seismology.
•Earthquakes are measured using observations from seismometers.
• Seismic waves are recorded on instruments called seismographs.
•The time, locations, and magnitude of an earthquake can be
determined from the data recorded by seismograph stations.

RICHTER MAGNITUDE SCALE:
•The Richter magnitude scale was developed in 1935 by Charles
F. Richter.
•Earthquakes with magnitude of about 2.0 or less are usually
called micro earthquakes; are generally recorded only on local
seismographs.
•Events with magnitudes of about 4.5 or greater, are strong
enough to be recorded by sensitive seismographs all over the
world.
•Great earthquakes have magnitudes of 8.0 or higher.
•On the average, one earthquake of such size occurs somewhere
in the world each year.

CAUSES :
Natural Causes of Earthquake:
•Tectonic Movement
•Volcanic Activity
•Pressure of gases in the interior
•Landslides and avalanches
•Faulting and folding in the rock beds are responsible for causing
minor earthquakes.

Man-made Earthquakes:
•The impounding of large quantities of water behind dams disturbs
the crustal balance.
•The shock waves through rocks set up by the underground testing
of Atom bombs or Hydrogen bombs may be severe to cause
earthquake.

Man-made Earthquakes:
•The impounding of large quantities of water behind
dams disturbs the crustal balance.
•The shock waves through rocks set up by the
underground testing of Atom bombs or Hydrogen
bombs may be severe to cause earthquake.

EFFECTS:
Destructive Effects:
•Earthquake causes dismantling of buildings, bridge and
other structures at or near epicenter.
•Rails are folded, underground wires broken.
•Earthquakes originate sea waves called Tsunamis.
•Earthquakes result in the formation of cracks and
fissures on the ground formation.
•The earthquakes cause landslides.
•Landslide due to earthquake may block valleys to form
lakes.

SEISMIC BELT:
Narrow geographic zone on the Earth's surface along
which most earthquake activity occurs.
The outermost layer of the Earth (lithosphere) is made
up of several large tectonic plates.
There are three main seismic belts in the world：
1.Circum-Pacific seismic belt
2.Alpine-Himalayan seismic belt
3.Ridge seismic belt

SEISMIC WAVES:
•Seismic waves are waves of energy that travel through the Earth's
layers, and are a result of earthquakes, volcanic eruptions, magma
movement, large landslides and large man-made explosions that
give out low-frequency acoustic energy.
•Seismic wave fields are recorded by a seismometer, hydrophone
(in water), or accelerometer.
P-waves:
•P-waves are a type of body wave, that travel through a continuum
and are the first waves from an earthquake to arrive at a
seismograph.
•Typical values for P-wave velocity in earthquakes are in the range
5 to 8 km/s.

S-WAVES:
• S-waves, secondary waves, or shear waves (sometimes called an
elastic S-wave) are a type of elastic wave.
• The S-wave moves as a shear or transverse wave, so motion is
perpendicular to the direction of wave propagation.
•Velocity tends to increase with depth and ranges from
approximately 2 to 8 km/s in the Earth's crust, up to 13 km/s in the
deep mantle.

L-WAVES:
• The third general type of earthquake wave is called a surface
wave, reason being is that its motion is restricted to near the ground
surface.
• Such waves correspond to ripples of water that travel across a
lake.
• The typical range of velocities is between 2 and 6 km/second.

PRECAUTIONS:
•First do the soil test. Structures will be constructed after testing the
soils compaction tendency.
•Design of the structures or buildings should be made by professional
engineer.
• Use rods according to the foundation type.
• The rod must provide necessary earthquake resistance to the building
or structure.
•Maintain the quality of cement, rod and sand. Provide necessary rod in
the joint of foundation and grade beam.
• This helps to provide extra earthquake resistance to the structures or
buildings.
•Check column and slab design requirements by the authority.

•For earthquake resistance purposes, there will be no connection in
the intersection of beam column.
•Columns of the structures or buildings need to be made strong to
provide needed resistance. Column size can be increased from the
foundation necessarily.

LANDSLIDES:
•A landslide is the movement of rock, debris or earth down a
slope.
•They result from the failure of the materials which make up the
hill slope and are driven by the force of gravity.
•Landslides are known also as landslips, slumps or slope failure.
•This is the most destructive and turbulent form of landslide.
• Flows have a high water content which causes the slope material
to lose cohesion, turning it into a slurry.

LANDSLIDES HAZARDS:
•Although landslides are primarily associated with mountainous
regions, they can also occur in areas of generally low relief.
• In low-relief areas, landslides occur as cut-and fill failures
(roadway and building excavations).
•Slope saturation by water is a primary cause of landslides.
•This effect can occur in the form of intense rainfall, snowmelt,
changes in ground-water levels.

Natural causes include:
• Elevation of pore water pressure by saturation of slope material
from either intense or prolonged rainfall and seepage
• Vibrations caused by earthquakes
• Undercutting of cliffs and banks by waves or river erosion
• Volcanic eruptions
Human causes include:
• Removal of vegetation
• Interference with, or changes to, natural drainage
• Leaking pipes such as water and sewer reticulation
• Modification of slopes by construction of roads, railways,
buildings, etc

5. Modification of slopes by construction of roads, railways,
buildings, etc
6. Mining and quarrying activities

ENGINEERING GEOLOGY

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