Engineering Geology for the practical applicaitons and field

Dr. N. VETRIVEL
D.C.E, B.E, M.Tech, Ph.D., LMISTE, LMIJRULA
Associate Professor –Water Resource Engineering
JIGJIGA UNIVERSITY -
IOT
Engineering Geology
(Geol-2078)
Regular Class

Introduction to geology: The earth & its interior, Geology & its applied branch, importance of
geology in water resource Engineering.
Crystals, minerals and rocks: Crystals and their characteristic features, minerals and physical
properties in mineral identification, origin, texture, primary structure and classification of main groups
of rocks
Geological work of natural agencies: Weathering, types of weathering, geological work of rivers
(streams), geological work of sea (ocean), geological work of wind, geological work of glaciers
Secondary structural features of rocks, landslides and earth quakes: Folds, faults, joints and
their engineering considerations, landslides and earth quakes causes and effects
Geological investigation: Phases and methods of investigation, geological considerations in
structures (dams, reservoirs, tunnels, road &bridges, buildings), Introduction and application of rock
mechanics
Quarries and their products: quarry types and controlling factors for selection of quarry site,
properties of building materials, common types of building stones with their properties and uses
Outline Syllabus

Weathering is a natural geological process
where rocks, minerals, and soils are broken
down or dissolved by exposure to natural
environmental factors such as air, water, and
biological organisms.
This process happens in situ, meaning that
the rocks and minerals are broken down
without being transported to another
location.
Weathering is an essential part of the
Earth's geological cycle and contributes to
soil formation, landscapes, and sediment.
Weathering

Agents of Weathering and Controlling Factors

Effects of Natural Agencies
• Geological Work by River
• During the life while flowing from head to mouth, the rivers are
capable of exerting greatly modifying influence over the topography
of the region through which they flow.
• The geological work by river may be broadly divided into three well-
defined phases: erosion, transport and deposition.

Geological Work by River
• Method of River Erosion
• By erosion is meant disintegration and decomposition of the
rocks and soil material by a natural agent through mechanical,
chemical, and other physico-chemical processes accompanied
by removal of the disintegrated or decomposed product to far
off places by the same agent.
• Stream and rivers are the most powerful sub aerial agents of
erosion. Others are wind and ice.

Feature of Stream Erosion
• Prolonged erosion by a river and the associated streams
produces many interesting and important surface features
along their channels directly and in the drainage basin in an
indirect manner some of these features develop, with the
passage of time to major geomorphological landforms.

Potholes
• Potholes
• These are various shaped depressions
of different dimensions that are
developed in the river bed by excessive
localized erosion by the streams. The
pot holes are generally cylindrical or
bowl shaped in outline these are
commonly formed in the softer rocks
occurring at critical location in the
bedrock of a stream.
• The formation process for a pothole
may be initiated by a simple plucking
out of a protuding or outstanding rock
projection at the river bed by hydraulic
action.

River Valleys
River Valleys
• A valley may be defined
as a low land surrounded
on sides by inclined hill
slopes and mountain.
Every major river is
associated with a valley
of its own. In fact, rivers
are responsible for the
origin, development and
modification of their
valleys through well-
understood process of
river erosion.

River Valleys
• (a) Origin. A river valley may have a modest origin when traced backward
in the geological history of the area. On a gentle sloping surface, river
water gets collected along lower level and flows as small streamlets. In a
short time small gullies are produced where rainwater gets naturally
collected from adjoining slopes, further erosion deepens and widens an
original gully that can accommodate bigger volumes of water.
• (b) Valley deepening It is achieved by cooperative action of all the
processes involved in erosion. Deepening is obviously caused due to
cutting down of the river bed.
• (c) Lengthening of river Valley. A peculiar type of process called
headword erosion is generally held responsible for lengthening of river
valleys.
• River capture (Piracy) A peculiar phenomenon of capture of draining
basin of one river by another river fast eroding its channel in headword
directions has been seen at many places.
• (d) Stream achieved valley widening. The stream cut down more their
channels and also remove away the loose soil and rocks from the banks
thereby widening the valley directly.

Georges and Canyons
• The process of valley
deepening often gives
rise to magnificent
surface features known
as Georges and canyons.
• Georges are very deep
and narrow valley with
very steep and high walls
on either side.
• A canyon is a specific
type of George where the
layers cut down by a river
are essentially stratified
and horizontal in
attitude.

Waterfalls
• These are defined as magnificent jumps made by stream or
river water at certain specific parts of their course where
there is a sudden and considerable drop in the gradient of
the channel.
• Many falls are easily attributed to unequal erosion of the
channel rocks within a short distance due to the inherent
nature of the rocks.

Stream Terraces
• These are bench like ledges or flat surfaces
that occur on the sides of many river valley.
From a distance they may appear as
successions of several steps of a big natural
staircase rising up the riverbed.

Sediment Transport by Rivers
• Every river receives enormous amount of material during its flow from head to
mouth. This material includes the rock and soil particles that the river acquires
by its own work of erosion along the channel. Heterogeneous type of materials
comprising of branches and trunks of trees washed down by rills and material
contributed from processes of mass wasting such as rock falls, soil creep, rain
wash and landslides from another distinct category of material that are
transported by river.

Sediment Transport by Rivers
• The load as all the material being transported in running water of a
stream or river, may thus be distinguished into following categories.
• Suspended load: It is made up of fine sand, silt and clay sediments
that are light enough to be transported in the stream water in a state
of suspension.
• Bed Load : This fraction of the river loads comprises the heavier
particles of sand, pebbles, gravels and cobbles and other type of
materials which are moved along the other side of the roads.
• The dissolved load This fraction include particles of material soluble in
water, which the river may gain due to its solvent action on the rock of
the channel. Numerous rivers from the land part carry calcium
carbonate, calcium sulphate and sodium Chloride and other
soluble salts from limestone, gypsum, anhydrite and rock salts etc.

Deposition by Rivers
• The entire load of a stream or a river will normally remain in
transport unless there is a change in one or other factor responsible
for its transport. The process of dropping down of its loads by any
moving natural agent is technically called deposition. Wind rivers,
glaciers and marine water are important natural agent that make
typical deposits.

Types of Deposits
• Alluvial fans and cones: These are cone shaped
accumulation of stream deposits that are commonly found
at places where small intermittent streamlets coming down
from hill slopes enter the low lands.
• Natural Levees: these are essentially riverbank deposits
made by a river along its bank during floods.
• The natural leeves are sometimes helpful in preventing
further flooding in a river provided the volume of water a
new prospective flood is not much higher than that of a
previous floods.

Types of Deposits
• Deltas: deltas are defined as alluvial deposits of roughly
triangular shape that are deposited by major river at their
mouth, i.e.. where they enter a sea.
• Channel deposits: Many streams are forced by some
natural causes to deposit some of their loads along the river
bed. These are so-called channel deposits. They are of great
economical use being the source of sands and gravel quite
suitable for use as construction materials.

River Meandering
• When a stream flows along a curved, zigzag path acquiring a loop-
shaped course, it is said to mender. Menders are developed mostly in
the middle and lower reaches of major stream where lateral erosion
and depositions along opposite banks become almost concurrent
geological activities of the stream, when a stream is flowing through
such a channel it cannot be assumed to have absolutely uniform
velocities all across its width. Thus the same river is eroding its
channel on the concave side and making its progress further inland
whereas on the convex side it is depositing. A loop shaped outline for
the channel is a natural outcome where a stream seen from a
distance.

The Oxbow Lakes
• In the advanced stages of a meandering stream only
relatively narrow strips of land separate the individual
loops from each other. During high-water times, as
during small floods, when the stream acquires good
volume of water, it has a tendency to flow straight,
some of the intervening strips of land between the
loops get eroded. The stream starts flowing straight in
those limited stretches, thereby leaving the loops or
loops on the sides either completely detached or only
slightly connected. This isolated curved or looped
shaped area of the river, which often contains some
water are called oxbow lakes.

Geological Works by Winds
• Air in motion is called Wind.
Wind is one of the three major
agents of change on the
surface of the earth, other
two being river and glaciers.
• Wind act as agent of erosion,
as a carrier for transporting
particles and grains so eroded
from one place and also for
depositing huge quantities of
such wind blown material at
different places. There are
three modes of activities i.e.
erosion, transportation and
deposition by wind.

• Wind Erosion
• Wind perform the work of erosion by at least three different methods:
Deflation, abrasion and attrition
• Deflation
• Wind posses not much erosive power over rocks the ground covered with
vegetation. But when moving with sufficient velocity over dry and loose sand
it can remove or swept away huge quantity of the loose material from the
surface. This process of removal of particle of dust and sand by strong wind
is called deflation.
• Wind Abrasion
• Wind becomes a powerful agent for rubbing and abrading the rock surface
when naturally loaded with sand and dust particles This type of erosion
involving rubbing, grinding, polishing the rock surface by any natural agent
is termed as abrasion.
• Attrition by wind
• The sand particles and other particles lifted by the wind from different
places are carried away to considerable distances. The wear and tear of load
particles suffered by them due to mutual impacts during the transportation
process is termed as attrition

Sedimentation Transport by wind
• Sources of sediments: Wind is an active agent of sediment transport in nature.
Materials of fine particle size such as Clay, silt and sand occurring on surface of the
earth are transported in huge volumes from one place to another in different
regions of the world.
• Methods of Transport: The wind transport is carried out mainly by two distinctly
different processes:
• Suspension: The light density clay and silt particles may be lifted by the wind from
the ground and are carried high up to the upper layer of the wind where they move
along with the wind. This is called transport in suspension.
• Siltation: the heavier and coarse sediments such as sand grains, pebbles and
gravels are lifted up periodically during high velocity wind only for short distance.
They may be dropped and picked up again and again during the transport process
Siltation is therefore, a process of sediment transport in a series of jumps.
• The transport power of wind: The transporting power of wind depends on its
velocity as also on the size, shape and density of the particles. The amount of load
already present in the wind at a given point of time also determines its capacity to
take up further load.

• Deposition by Wind Aeolian deposits.
• Sediments and particles once picked up by the wind from any source on the
surface are carried forward for varying distances depending on the carrying
capacity of the wind. Wherever and whenever the velocity of wind suffers a check
from one reason or another a part or whole of the wind load is deposited at that
place. These wind made deposits may ultimately take the shape of landform that
are commonly referred as aeoline deposits. These are of two main types of
deposits Dunes and loess.

• (a) Dunes These are variously shaped deposits of sand-grade
particles accumulated by wind. A typical sand dune is defined as
broad conical heap. A dune is normally developed when a sand
laden wind comes across some obstruction The obstruction
causes some check in the velocity of the wind , which is
compelled to drop some load over, against or along the
obstruction when the process is continued for a long time, the
accumulated sand takes the shape of mound or a ridge. A typical
dune is characterized with a gentle windward side and a steep
leeward slope.

• Loess: The term Loess is used for wind blown deposits of silt and clay
grade particles. Typically Loess is unconsolidated, unstratified and
porous accumulation of particles.
• Strong winds blowing over very extensive area of deserts, outwash
plains and soil loosened by plough pick up vast amount of fine grade
particles for transportation in suspension, when such dust laden
winds passing over steppes and other flat surfaces are intercepted by
precipitation they drop their entire loads on the surface below. This
process is repeated for years. Accumulations of such sediments over
years have resulted in the present loess deposits.

Geological Work of Groundwater

Geological Work of Groundwater
• Ground water like surface water, is also a very powerful
natural agent responsible not only for modifying the
existing features but also for creating many other
geological features on and below the surface of the earth.
• Geological works of ground water may be conveniently
studied under two headings namely chemical work and
mechanical work.

Geological work of Groundwater
• Water is a great solvent. Groundwater becomes an active agent of
dissolution of many rocks like lime stone, dolomites, gypsum, rock
salt and the like with which it comes into contact during its
downward journey below the surface. It has been observed that
water dissolves limestone at a variable rate that depends upon its
temperature, composition and above all its carbon dioxide content.
• The dissolution of soluble rocks by groundwater is controlled by a
number of factors such as climate, geological structure, topography,
porosity and permeability of rocks, composition of rocks,
composition of ground water, especially its salts and gaseous
content , flow velocity, temperature, pressure, pressure and depth
at which the water comes in touch with the rocks.

• Quite a number of forms are developed due to solvent action of
water few are mentioned as below:
• Dolines: These are also termed as swallow holes, sink holes and
sometimes simply as sinks. A typical dolines is circular or oval
depression, which when followed in depth becomes bowl-shaped or
cylindrical in cross section.
• Caves: these may be defined as naturally carved out underground
cavities of various dimensions that always have horizontal opening
on the surface. They are similar to tunnels with the exception that a
cave does not normally have an exit on the other end.
• Blind Valley: A blind valley is a valley like feature where a stream
flowing through it in the upper reaches suddenly disappears in the
lower reaches.

• Groundwater is also an active agent of deposition in regions of proper
climate and geology. These deposits are typically found to occur in
caves and other underground openings and also fissures and crakes in
the form of mineral bands, mineral streak or even as distinct mineral
layer. Among the minerals very often deposited from the groundwater
by precipitation etc. may be mentioned varieties of calcite, silica,
flourite and barite.
• The two most commonly known cave deposits are stalactites and
stalagmites.
• Stalactites: are carbonate projections that hang down from the roof of
the caves. They may acquire fantastic shapes like slender rods and
cones with flattered bases attached firmly with the roof.
• Stalagmites: are also groundwater deposits of carbonate rich droplets
from ground upwards.

• Mechanical Work: Subsurface
water is also invariably
characterized with some motion
due to one or another reason for
instances, under the influence of
gravity in the zone of aeration and
that of hydrostatic head in the
Aquifer and underground streams.
The velocity of subsurface flow
however, is much less when
compared to surface water. Hence
the mechanical work of subsurface
water is more in theory than in
practice.

Geological Work of Oceans
• Marine water is spread over more than two third of the earth’s surface and is
classed among the most powerful geological agents operating on the earth.
Marine geology is fast acquiring the status of a separate branch of geology
where the study of oceans, as said above has become the domain of specific
branch of science.
• Like other geological agencies, seawater also acts as an agent of erosion,
transport and deposition. Since seawater is almost confined within
boundaries and broadly standing in nature unlike river that flows downwards,
the mechanism of geological work of sea differ in detail from that of river. All
the geological work performed by marine water is due to regular and
irregular disturbances taking places in the body of water. Mostly in the surface
layer and distinguished as waves and currents.

• Marine Erosion
• Marine water erodes the rocks at the shore and elsewhere with
which it comes in contact in a manner broadly similar to that of
stream water. The work of erosion is accomplished in three ways.
Hydraulic action, abrasion, and corrosion.
• Hydraulic Action: This is the process of erosion by water involving
breaking, loosening and plucking out of loose, disjointed blocks of
rocks from their original places by the strong forces created by the
impact of sea waves and currents.
• Marine Abrasion This involves the rubbing and grinding action of
seawater on the rocks of the shore with the help of sand particles
and other small fragments that are hurdled up again these rocks.
• Corrosion: It is the solvent action of seawater which is particularly
strong in environment where the shore is of vulnerable chemical
composition.

• Feature of Marine Erosion:
• Some very common features of marine erosion are headlands, bays,
sea cliff and wave-cut terraces.
• Headlands and Bays
• In an originally uniform sloping shoreline composed of materials of
unequal hardness, the softer rocks get eroded easily and quickly.
Seawater enters the inland spaces so created along the shore, These
form the bays. The stronger rocks, however, resist erosion to a great
extent and stand for a considerable time. These may get smoothened
and variously modified but still stand as projecting parts of original as
headlands.

• Sea Cliffs
• A Sea cliff is seaward facing steep front of a moderately high
shoreline and indicates the first stage of the work of waves on the
shore rocks. There may be a number of sea cliffs seen on a shore
line. They are outstanding rock projection having smoothened
seaward sloping surface.
• Wave-Cut Terraces
• A wave-Cut Terrace is a shallow shelf type structure, carved out
from the shore rocks by the advancing sea waves. The waves first
of all cut a notch where they strike against the cliff rock again and
again. The notch is gradually extended backward to such a depth
below the overlying rock that the latter becomes unsupported from
below. The cliff eventually falls down along the notch. A platform or
bench is thus created over which the seawater may rush
temporarily and periodically. The resulting structure is called a
wave curt terrace.

Marine Deposition
• Seas are regarded as most important and extensive sedimentation basins, this becomes
evident from the fact that marine deposits of practically of all the geological ages. These
deposits are exposed at many places in almost all the continents all the marine deposits are
conveniently classified into two groups: Shallow water deposits and Deep-water deposits.
• Shallow Water( Neritic Deposits)
• These include marine deposits laid down in neritic zone of the sea, which extends from the
lowest tide limit to the place of the continent shelf where the slope becomes steeper.
• (i) Beaches: These are loose deposits made by the sea near the shore from the materials
eroded from nearby regions. The lower margin of a beach is commonly beneath the waves
whereas the upper margin is a few meter above the still water. Waves and currents play a
greater role in formation of a beach.
• (ii) Splits and Bars: These are ridge shaped deposits of sand and shingle that often extends
across the embayment.
• (iii) Tombola: It is the form of marine deposit that connects a headland and an island or one
island with another island.

Marine Deposition
• Deep Water Deposits: These deposits consists mostly
of Mud and oozes and are called as pelagic deposits.
The oozes that form bulk of some such deposits
consist of small organisms known collectively as
planktons. Death and decay of these organisms and
plants followed by their accumulation in regular and
irregular shapes These deposits are commonly called
as reefs.

Marine Deposition
• Coral Reefs: These are peculiar type of ridge like
marine deposits that have been found due to
accumulation of dead parts of certain type of sea-
organisms. Corals a typically a calcium secreting
organisms predominate the source for such reefs
hence they are commonly designated as coral
reefs.
• Economic Importance: reefs have acquired
considerable strategic and economic importance
during recent years. Strategically some of the reef
deposits are ideal as air bases in the vast expanse
of sea. Economically, the old reef are known to be
the source rock for the oil deposits.

Geological Work of Glaciers
• Glaciers are defined as huge bodies of ice characterized with downward and outward
movement. They are formed in suitable climate and topography in favorably located
regions.
• Under its own load after falling over an area for considerable time, the snow undergoes
a process of progressive compaction. With continued compaction due to increasing
mass of snow from above after every snowfall,firn undergoes further change towards a
very compact, dense, coarsely crystalline mass. This condensed compacted and solid
mass of snow is defined as ice. A glacier is composed mostly of ice and firn.

Geological Work of Glaciers
• Glaciers like other geological agencies, perform their work in three ways: erosion, transport and
deposition. Glaciers have been particularly active in recent geological past and are held
responsible for development and modification of many land features on the globe.
Glacier Erosion: Erosive work is accompanied by glaciers in two ways: by plucking and by abrasion.
Glacier Plucking
• It may be broadly defined as loosening and breaking of rock masses by the pressure of glacier ice.
It is also called as glacier quarrying. Thus, a block is torn out of position and moves away long
with the glacial ice and leaving behind a rough and rugged rock surface.
• These plucked-out surfaces are observed conspicuously in many glaciated areas on the steeper
sides of hill-like structures called the stross and Lee forms.
Glacial Abrasion.
• It is the rubbing, scratching, grooving and polishing action of the glaciers on the rock surface
along or over which these ice mass happens to move. Ice itself is capable of abrading the soft
rocks only. But when it is carrying along its stone fragments and rock pieces, sand, silt and clay, it
acts as a powerful abrading medium.

Features of Glacial Erosion
Whaleback forms:
• These are commonly called roaches moutonee and may be
described as glacially eroded residual hillocks or hummocks. One
side of such a feature rises up very gently and is smooth, curved
and much longer than wide. The other side of the same hillock
may be rugged, rough and steep. The direction of ice is indicated
by gentle slope.
Crag and Tail:
• When in the course of glacier a highly resistant rock stands as an
obstruction, it generally retards the erosive action of ice on the
soft bed rock sheltered behind the obstruction thus a peculiar
feature results in which the obstructing rock facing the ice is
known as CRAG. The sheltered and softer bed rock is termed as
the TAIL . And the combined structure as CRAG and TAIL.

• Glacial Valley: Most Valley-glaciers originate and disappear in pre-existing valleys
carved out by stream. These glaciers stream valley, however are eventually so much
modified in their longitudinal and transverse profile because of prolonged glacial
erosion that their origin due to stream erosion may become doubtful. In their
transverse profile, glacial valleys presnt a typical U-Shaped outline, tending more
towards a semi-circle.
• Hanging Valleys: A valley glacier may have one or more small tributary glaciers
meeting it from sides. The rate of glacial erosion being more in the main valley glacier, a
time may come when the side glacier are no longer in contact with main valley. Their
small valleys are gradually left higher at junctions with main valley. Such Tributary
glacial valleys are called Hanging Valleys.

• Cirques (Corries): A cirque may be defined as a
semicircular or half-bowl shaped depression within an
otherwise uniform glaciated valley slope. Such a
depression is invariable bounded on sides by Steep
Wall. Cirques range in diameter from a few meters to
a few kilometers and occur commonly at the heads of
valley glaciers.
• Fiords: these are highly over deepened narrow
elongated valley-like channels that have been
excavated by the glacial ice between high walled rock.
It is typical of many of the fiords that they reach the
coastline below the sea level. Due to this reason, many
of the fiord become inland extensions of the sea.

• Glacial erosion modifies the original form of mountainous
regions to a great extent with development of valley and
cirques. Further growth of these glacial excavation assisted by
mechanical disintegration results in the development of
certain peculiar forms. Are’tes, horns and cols are some such
noteworthy features.
• An Are’te is a knife-edge sharp and narrow crest of a glaciated
mountain. A horn is pyramidal, multi-facetted projecting form
in mountainous region. A col is a pass or depression on a
ridge in a glaciated mountain.

Glacial Transport
• Glaciers are defined as moving bodies of ice, As such they are capable
of transporting any load they gather during the movement. Such loads
consists of all sorts of heterogeneous materials. The load being
carried by glaciers may be located along its base or it may be
embedded within its body. The rate of movement of the glacial load
depend on the position that the load material occupies in a glacier.

Glacial Deposits
• Glaciers carry enormous quantities of hetrogeneous load with them
which is kept in a state of transport till the conditions are favorable or till
the glacier reach their lower ends or terminal points. the load is then
deposited or dropped and may form huge accumulations of glacial debris
varying shapes and characters.
• Drift: All such accumulation of glacial debris that have been deposited by
glaciers directly or indirectly from glacial meltwaters are collectively
known as drift. This is further distinguished into two types: Till and Fluvio-
glacial drift.
• Till it is also called unstratified drift and is the most common form of
glacial deposit. Till may consist of an unassorted mixture of boulders and
clay having an undisputed glacial origin.

Engineering Geology for the practical applicaitons and field

More Related Content

Similar to Engineering Geology for the practical applicaitons and field (20)

More from VetrivelNagarajan2 (7)

Recently uploaded (20)

Engineering Geology for the practical applicaitons and field