CE-6301 Engineering Geology Two Marks Questions With Answers 2014

Anna University, Chennai


UNIT – I Introduction

1.Explain about Earth Materials and Processes.

The materials that make up the Earth are mainly rocks (including soil, sand, silt, dust). Rocks in turn are composed of minerals. Minerals are composed of atoms, Processes range from those that occur rapidly to those that occur slowly Examples of slow processes

Formation of rocks

· Chemical breakdown of rock to form soil (weathering

· Chemical cementation of sand grains together to form rock


· Recrystallization to rock to form a different rock (metamorphism)

· Construction of mountain ranges (tectonism)

· Erosion of mountain ranges

· Examples of faster processes

· Beach erosion during a storm.

· Construction of a volcanic cone

· Landslides (avalanches)

· Dust Storms

· Mudflows

Processes such as these are constantly acting upon and within the Earth to change it.

Hydrologic Cycle

Rain comes from clouds - falls on surface, picks up sand, silt and clay,

carries particles to river and into ocean. Water then evaporates to become

clouds, which move over continents to rain again.

Internal Processes

Processes that produce magmas, volcanoes, earthquakes and build

mountain ranges. Energy comes from the interior of the Earth, Most from radioactive decay - nuclear energy.

2.Explain about Earth structure.

The Earth has a radius of about 6371 km, although it is about 22 km

larger at equator than at poles.

Internal Structure of the Earth:

Density, (mass/volume), Temperature, and Pressure increase with depth in the Earth.

Compositional Layering

Crust - variable thickness and composition

Continental 10 - 50 km thick

Oceanic 8 - 10 km thick

Mantle - 3488 km thick, made up of a rock called peridotite

Core - 2883 km radius, made up of Iron (Fe) and small amount of

Nickel (Ni)

Physical Properties

· Lithosphere - about 100 km thick

(deeper beneath continents)

· Asthenosphere - about 250 km thick to depth of 350 km - solid rock, but

soft and flows easily.

· Mesosphere - about 2500 km thick, solid rock, but still capable of flowing.

· Outer Core - 2250 km thick, Fe and Ni, liquid

· Inner core - 1230 km radius, Fe and Ni, solid

All of the above is known from the way seismic (earthquake waves) pass through the Earth as we will discuss later in the course.

Surface Features of the Earth

Oceans cover 71 % of Earth's surface -- average depth 3.7 km. Land covers remaining surface with average of 0.8 km above sea level

Ocean Basins

Continental Shelf, Slope, and rise

Abyssal Plains Oceanic ridges Oceanic Trenches Plate Tectonics

Tectonics = movement and deformation of the crust, incorporates older theory of continental drift.

Plates: are lithospheric plates - about 100 km thick, which move around on top of the asthenosphere.

3.Geological work of Groundwater?

Groundwater makes up about 1% of the water on Earth (most water is in

oceans). But, groundwater makes up about 35 times the amount of water in lakes and streams. Groundwater occurs everywhere beneath the Earth's

surface, but is usually restricted to depths less that about 750 meters.

The Water Table


The rate of groundwater flow is controlled by two properties of the rock:

porosity and permeability.


Porosity is the percentage of the volume of the rock that is open space

(pore space)

usually have higher porosity than finegrained


Permeability is a measure of the degree to which the pore spaces are interconnected, and

the size of the interconnections. Low porosity usually results in low permeability, but Groundwater

high porosity does not necessarily imply high permeability.

Movement in the Zone of Aeration

Rainwater soaks into the soil where some of it is evaporated, some of it adheres to grains in thesoil by molecular attraction, some is absorbed by plant roots, and some seeps down into the saturated zone. During long periods without rain the zone of aeration may remain dry.

Movement in the Saturated Zone

In the saturated zone (below the water table) water percolates through the interconnected pore spaces, moving downward by the force of gravity, and upward toward zones of lower pressure.Where the water table intersects the surface, such as at a surface stream, lake, or swamp, the groundwater

returns to the surface.


An aquifer is a large body of permeable material where groundwater is present in the saturated zone.

Unconfined Aquifers - the most common type of aquifer, where the water table is exposed to the Earth's atmosphere through the zone of aeration. Most of the aquifers depicted in the drawings so far have been unconfined aquifers.

Confined Aquifers - these are less common, but occur when an aquifer is confined between layers of impermeable strata. A special kind of confined aquifer is an artesian system, shown below. Artesian systems are desirable because they result in free flowing artesian springs and artesian wells. Geologic Activity of Groundwater

Dissolution - Recall that water is the main agent of chemical weathering. Groundwater isan active weathering agent and can leach ions from rock, and, in the case of carbonate rocks like limestone, can completely dissolve the rock.

4. Explain about EARTHQUAKES

Most of us must have personally experienced earthquakes, and are,

therefore, aware of them. Earthquake is something which causes the shaking of the Earth ; and as such, all our buildings and structures erected on the Earth's surface start trembling, as and when a quake comes. An earthquake, is therefore, defined as a natural vibration of the ground (or the Earth's crust) produced by forces, called earthquake forces or seismic forces.


In fact, the term epicentre is important as it represents the point on the Earth, where the earthquake waves reach for the first time, after they are generated from the focus. The area around the epicentre will be subjected to earthquake vibrations, and is generally indicated as epicentral area.

Causes of Earthquakes and Their Types:

(1)Tectonic earthquakes ; and

(2)Non-tectonic earthquakes.

Earthquake Waves, Their Recording and Types:

P-Waves (i.e. Primary Waves). The P-waves are com-pressional in nature, and travel like sound waves

S-waves (i.e. Secondary Waves). These waves are transverse or distortional like those of light waves. The particles, therefore, travel in a direction at right angles (i.e. transverse) to the direction of propagation of the wave

L-waves (Le. Long Waves). These waves travel alongthe Earth's surface, following a circumferential path.

Intensity and Magnitude of an Earthquake:

Intensity of an Earthquake. Intensity of an earthquake may be defined as the rating of an earthquake based on the actual effects produced by the quake on the Earth.

Intensity Scale For Earthquakes with Approximately Corresponding

Inte n-

sity clas s

Maximum Acceleration of

the ground in mm/sec2

Name of the shock

Effects observed

Magnitude (M) corres- ponding to



sity reached




Recorded only by sensitive seismographs

3.5 to




Recorded by all


and may be felt by some sensitive persons at rest.




Commonly felt by all


at rest, especially on upper floors.-





Commonly felt by all

4.3 to



either at rest or in motion ; nocking of loose objects in-

cluding standing vehicles




Fairly strong

Generally felt ; most sleeping

persons are awakened ;

ringing of bells




Trees sway and all suspended

objects swing ; fall of weak

plasters : general panic ;

damage by overturning and

falling of loose objects.

4.9 to 5.5



Very strong

Damages to buildings

producing cracks in walls, etc., fall of chimneys ;


alarm and panic.

5.5 to 6.2

Magnitude (M) of an Earthquake. Magnitude of a tectonic earthquake may be defined as the rating of an earthquake based on the total amount of energy released when the over-strained •

The Assam Earthquake (1897. . The Kangra Earthquake (1905). The Bihar Earthquake (1934).

The Quetta Earthquake in Baluchistan (1935

Assam Earthquake (1950)

5. Explain about Weathering process

The physical and chemical conditions of rocks are altered when they are exposed to the atmosphere. Such an altered product is known as weathered material and the process involved is called weathering. When weathering is accompanied by erosion it results in the denudation of an area.


Weathering occurs in three ways. Rocks break due to stress developed in ti ,em, mechanically. Rocks decay due to chemical reactions on them. Organisms by way of growth and movement alter the rocks physico-chemical conditions, although these three ways of weathering seem to be separate entities they are interconnected. And further .one process induces the other process. As such, these three ways are termed: 1. Physical or Mechanical weathering, %. Chemical weathering and 3. Biotic weathering.


Rocks and minerals are disintegrated into smaller and smaller particles. The processes which bring about the disintegration without any chemical reaction as a response to the change in conditions of environment are collectively known as mechanical or physical weathering. The chief processes that result in mechanical weathering are Frost Action. Exfoliation etc.







The transformation of rocks into new substances is known as chemical weathering. Natural chemical agents alter the chemical composition, the structure' and the physical, appearance of the original. It is a complex process, involving chemical reactions, of responses of rocks to water and gases of atmosphetiM at or near the

surface of the Earth's crust. It leads to decomposition.

6. Explain about Wind As A Geologic Agent?

Moving air mass is known as the wind. Wind produces varieties of landforms ( by erosion and deposition ).

ABRASION: The wearing down of solid rocks by the impact of wind borne particles is known as cdrrasion.


Sand grains and other particles lifted by the wind from different places.


CAUSES: The wind borne particles may be deposited for the following


1. Any obstruction to wind

2. Reduction in velocity

3. Increased load

4. Rain

Unit – 2

1. what are the properties of minerals?

Physical properties of minerals allow us to distinguish between minerals and

thus identify them, as you will learn in lab. Among the common properties used are:

· Habit - shape

· Color

· Streak (color of fine powder of the mineral)

· Luster -- metallic, vitreous, pearly, resinous (reflection of light)

· Cleavage (planes along which the mineral breaks easily)

· Density (mass/volume)

· Hardness

Based on hardness scale as follows:

1. Talc

2. gypsum (fingernail)

3. calcite (penny)

4. fluorite

5. apatite (knife blade)

6. orthoclase (glass)

7. quartz

8. topaz

9. corundum

10. Diamond

2.Explain about composition of minerals.

The variety of minerals we see depend on the chemical elements available to form them.

In the Earth's crust the most abundant elements are as follows:

1. O, Oxygen 45.2% by weight

2. Si, Silicon 27.2%

3. Al, Aluminum 8.0%

4. Fe, Iron 5.8%

5. Ca, Calcium 5.1%

6. Mg, Magnesium 2.8%

7. Na, Sodium 2.3%

8. K, Potassium 1.7%

9. Ti ,Titanium 0.9%

10. H, Hydrogen 0.14%

11. Mn, Manganese 0.1%

12. P, Phosphorous 0.1%

3.What are the Mixture of minerals?

Mixtures or aggregates of minerals are called rocks. There are three basic kinds of rocks, each type is determined by the process by which the rock forms.

· Igneous Rocks - form by solidification and crystallization from liquid rock, called magma.

· Sedimentary Rocks - form by sedimentation of mineral and other rock fragments from water, wind, or ice and can also form by

chemical precipitation from water.

· Metamorphic Rocks - form as a result of increasing the pressure and/or

temperature on a previously existing rock to form a new rock.

Each of these rock forming processes results in distinctive mineral assemblages and textures in the resulting rock. Thus, the different mineral assemblages and textures give us clues to how the rock formed

4.Explain about formation of minerals?

Minerals are formed in nature by a variety of processes. Among them are

· Crystallization from melt (igneous rocks)

· Precipitation from water (chemical sedimentary rocks, hydrothermal ore


· Biological activity (biochemical sedimentary rocks)

· Change to more stable state - (the processes of weathering, metamorphism,

and diagenesis).

· Precipitation from vapor. (not common, but sometimes does occur around

volcanic vents)

Since each process leads to different minerals and different mineral

polymorphs, we can identify the process by which minerals form in nature. Each process has specific temperature and pressure conditions that can be determined from laboratory experiments.

Example: graphite and diamond, as shown previously.


1.Briefly explain about Igneous Rock

Igneous Rocks are formed by crystallization from a liquid, or magma. They include two types

· Volcanic or extrusive igneous rocks form when the magma cools and crystallizes on the surface of the Earth.

· Intrusive or plutonic igneous rocks wherein the magma crystallizes at depth in the Earth.

· Magma is a mixture of liquid rock, crystals, and gas.

Types of Magma

Chemical composition of magma is controlled by the abundance of elements in the Earth. Si,

Al, Fe, Ca, Mg, K, Na, H, and O make up 99.9%. Since oxygen is so abundant, chemical analyses are usually given in terms of oxides. SiO2 is the most abundant oxide.

1. Basaltic or gabbroic -- SiO2 45-55 wt%, high in Fe, Mg, Ca, low in

K, Na

2. Andesitic or Dioritic -- SiO2 55-65 wt%, intermediate. in Fe, Mg, Ca, Na, K

3. Rhyolitic or Granitic -- SiO2 65-75%, low in Fe, Mg, Ca, high in K, Na.

Gases - At depth in the Earth nearly all magmas contain gas. Gas gives magmas their explosive character, because the gas expands as pressure is reduced.

Mostly H2O with some CO2

Minor amounts of Sulfur, Cl , and F

Rhyolitic or granitic magmas usually have higher gas contents than basaltic or gabbroic magmas.

Temperature of Magmas

Basaltic or Gabbroic - 1000-

1200oC Andesitic or Dioritic -

800-1000oC Rhyolitic or

Granitic - 650-800oC.

Eruption of Magma

When magmas reach the surface of the Earth they erupt from a vent. They

may erupt




Igneous rocks cooled at depth. Name comes from Greek god of the underworld – Pluto

Dikes are small (<20 m


wide) shallow intrusions that show a discordant

relationship to the rocks in which they intrude.

Sills are also small (<50 m thick) shallow intrusions that show a concordant relationship with the rocks that they intrude.

2.Briefly explain about sedimentary rocks.

Rivers, oceans, winds, and rain runoff all have the ability to carry the particles washed off of eroding rocks. Such material, called detritus, consists of fragments of rocks and minerals. When the energy of the transporting current is not strong enough to carry these particles, the particles drop out in the process of sedimentation. This type of sedimentary deposition is referred to as clastic

sedimentation. Another type of sedimentary deposition occurs when material is dissolved in water, and chemically precipitates from the water. This type of sedimentation is referred to as chemical

sedimentation. A third process can occur, wherein living organisms extract ions dissolved in water to make such things as shells and bones. This type of sedimentation is called biogenic sedimentation. Thus, there are three major types of sedimentary rocks: Clastic Sedimentary Rocks, Chemical Sedimentary Rocks, and Biogenic

Sedimentary Rocks

Clastic Sediments

Classification - Clastic sedimentary particles are classified in terms of size

Name of


Size Range



Consolidated Rock


>256 mm


Conglomerate or Breccia (depends on rounding)


64 - 256 mm



2 - 64 mm



1/16 - 2mm




1/256 - 1/16 mm




<1/256 mm


Claystone, mudstone, and shale

The formation of a clastic sedimentary rock involves three processes:

Transportation - Sediment can be transported by sliding down slopes, being picked up by the wind, or by being carried by running water in streams, rivers, or ocean currents. The distance the sediment is transported and the energy of the transporting medium all leave clues in the final sediment that tell us something about the mode of transportation

Deposition - Sediment is deposited when the energy of the transporting medium becomes too low to continue the transport process. In other words, if the velocity of the transporting medium becomes too low to transport sediment, the sediment will fall out and become deposited. The final sediment thus reflects the energy of the transporting medium

Diagenesis - Diagenesis is the process that turns sediment into rock. The first stage of the process is compaction. Compaction occurs as the weight of the overlying material increases. Compaction forces the grains closer together, reducing pore space and eliminating some of the contained water. Some of this water may carry mineral components in solution, and these constituents may later precipitate as new minerals in the pore spaces. This causes cementation, which will then start to bind the individual particles

together. Further compaction and burial may cause recrystallization of the minerals to make the rock even harder.

Other conditions present during diagenesis, such as the presence of absence of free oxygen may cause other alterations to the original sediment. In an environment where there is excess oxygen (Oxidizing Environment) organic remains will be converted to carbon dioxide and water. Iron will change from Fe2+ to Fe3+, and will change the color of the sediment to a deep red (rust) color. In an environment where there is a depletion of oxygen (Reducing Environment), organic material may be transformed to solid carbon in the form of coal, or may be converted to hydrocarbons, the

source of petroleum

3. Explain about Metamorphic Rocks

From greek meta-change


Types of metamorphic;

1.Thermal metamorphic

2.Dynamic metamorphic

3.Dynamic –thermal metamorphism.

Unit – 4

1.What are the features of Topographic maps? Features of Topographic Maps: TOPOGRAPHY (RELIEF):

- printed in brown

- contour lines shows hills, mountains, plains, etc.


- printed in blue

- includes oceans, lakes, ponds, rivers, canals, etc.


- printed in black

- human-make works such as roads, railroads, buildings, land boundaries, etc.

2.What are the types of Folds? Folds:

When rocks are deformed plastically, they are bent into folds. There are Three Main Types of Folds:


This is when layers are folded upwards in what looks

like an arch. The layers are symmetrical (look alike) to either side of its center.


This is when the rock layers are folded downward.


This is when the rock layer has a gently

dipping bend in the horizontal rock layer.

3. What are the types of Faults? Faults:

When rocks are deformed (broken) brittly, they are displaced along fractures

called FAULTS.

Dip-Slip Faults:

Movement along dip-slip faults is vertical; one side moves up and the other side moves down.

The two types of Dip-Slip Faults are Normal Faults and Reverse Faults:

Normal Fault:

The hanging wall has slipped down in comparison to the foot wall.

Reverse Fault: The hanging wall has slipped up in comparison to the foot wall.

Strike Slip Fault: Two layers of rock are shifted horizontally or parallel to the fault plane.

4.Explain about Joints? Types of joints:

Systematic joints

Non-systematic joints

Strike joint Dip joint Oblique joint Cross joint

Longitudinal joint


1.Geological considerations involved in the construction of Roads

• Topography of the region – topographic maps, valleys, hills , slope,

• Hilly region – aerial surveys - contour maps preparation is required

Litho logical characters of the rocks

Type and nature of the rocks and sediments of the area.

• Rock types available for laying roads divided in to 1. massive consolidated

2. loose consolidated

• What type of construction material

• Transport with ease and economy

Massive Group of rocks

• Igneous rocks – granite , Basalt

• Sedimentary rocks – Sand stones, quartzite

• Metamorphic rocks – Gneisses, Marbles, schists, slates.

Unconsolidated group of rocks

Soil investigations – mode of origin, texture, structure, bearing capacity

Residual soils – homogenous and exhibit less complications as compared to transported soil

Presence of clay – investigated thoroughly in case of residual soil

Clay minerals may swell considerably in contact with water - thus prove to be dangerous for the stability of the road or railway.

Structural features of the rocks

• Geological structures – sedimentary origin – very important bearing on the design of the cuts as well as on the stability of a road as a whole.

• Plane of weakeness – joints , bedding planes.

• Dip and strike

• cut made parallel to dip of beds – little danger – quite safe and preferable.

Structural features

• Cut made parallel to the strike of beds – complications arise

• Firstly – strata plunge steeply across cutting

• Secondly – the slope of cutting is unequal on sides.

• Road made parallel to the dip of the beds – safe – do not need any additional treatment.

• Cuts are made either parallel or inclined to strike- special measures will have to taken to stabilise the cut slopes.

• Joints

• Faults –

Ground water conditions of the area

• Determining the position of water table

• Water bearing properties ( porosity and permeability )

• Grounwater in many cases redude the bearing capacity of the foundation soil – sub grade failures.

Construction of roads and railways in complicated regions.

• Roads in hilly regions

• Roads in Marshy regions

• Roads in water – logged areas.

• Roads in frost regions

2.Design and construction of BULIDINGS

• Multistoreyed buildings

• pillars transmit the loads to the underground soil through the foundation-constructed in different shapes – raft foundation , pile foundation- depending upon the bed rock.

• The greater is the building load , stronger should be the underground soil, to with stand the load.

Basic requirements of a building foundation

• The foundation should be capable of bearing the design loads without exceeding permissible stresses on the foundation material such as concrete.

• Building load uniformly to the subsoil zone.

• The building foundation should be laid on stable ,hard soil or hard rock to control shrinkage of the sub soil zone.

Building foundations on soils

Soil testing

Bearing capacity

Building foundations carried to the Deeper hard rocks

• Geophysical surveys – Resistivity survey

Buildings founded on surface bed rocks

• General distribution of load

• Reduction of differential settlement

• Stability against sliding and overturning

• Reduction of distress against soil movement

Remote Sensing

Definition and Origin

Generally speaking, Remote Sensing is the acquisition and analysis of information about objects or phenomena from a distance. In regards to the discipline of geography, it is the acquisition and analysis of information about the Earth (or other planetary bodies) through the use of computer and sensor systems via electromagnetic radiation. It could be argued that Remote Sensing originated with any human gaining a high perspective of

an area, but in a more sophisticated sense it began in the 1830s with the invention of the camera. Major advancements were made during World War II with the development of RADAR (Radio Amplified Detection and Ranging) and SONAR (SOund NAvigation and Ranging). Side Looking

Airborne Radar (SLAR) was also invented during World War II and its product is a high resolution image.

Early Developement

In the Late 1950's, fixed wing aerial photography was extensively

developed. In the early 1960's, the space race had begun between Russia and the United States. Image based satellite systems were developed, especially with regard to military spy satellites and civilian weather

observation satellites. Radar and was vastly improved upon. Synthetic Aperture Radar (SAR) systems were developed was also developed during this time.

Modern Era

Remote sensing came of age in the 1970's with the refinement of

satellite imaging. In 1972 the Earth Resources Technology Satellite

(ERTS) was renamed to LANDSAT (NASA). The sensor had an 80 meter/pixel spatial resolution. In 1975, constant image download was available from LANDSAT, with an 18 day temporal resolution (passing over the same geographical area every 18 days). So much data became available, that Earth Resources Observation Systems (EROS) data center was established in South Dakota. Initial cost for four band (Red, Blue, Green and Infrared) .

2. Electromagnetic Spectrum


3. Design and considerations of dams?

Basic requirements of an embankment dam.

Dams are a critical and essential part of the Nation’s infrastructure for the

storage and management of water in watersheds. To meet the dam safety requirements, the design, construction, operation, and modification of an

embankment dam must comply with the following

technical and administrative requirements:

(1) Technical requirements.

• The dam, foundation, and abutments must be stable under all static

and dynamic loading conditions.

• Seepage through the foundation, abutments, and embankment must be controlled and collected to ensure safe operation. The intent is to prevent excessive uplift pressures, piping of materials, sloughing removal of material by solution, or erosion of this material into cracks, joints, and cavities. In addition, the project purpose may impose a limitation on allowable quantity of seepage. The design should include seepage control measures such as foundation cutoffs, adequate and nonbrittle impervious zones, transition zones, drainage material and blankets, upstream impervious blankets, adequate core contact area, and relief wells.

• The freeboard must be sufficient to prevent overtopping by waves and include an allowance for settlement of the foundation and embankment.

• The spillway and outlet capacity must be sufficient to prevent over- topping of the embankment

by the reservoir.

(2) Administrative requirements.

• Environmental responsibility.

• Operation and maintenance manual. EM 1110-2-2300

30 Jul 042-2

• Monitoring and surveillance plan.

• Adequate instrumentation to monitor performance.

• Documentation of all the design, construction, and operational


• Emergency Action Plan: Identification, notification, and response


• Schedule for periodic inspections, comprehensive review, evaluation, and modifications as


c. Embankment.

Many different trial sections for the zoning of an embankment should

be prepared to study utilization of fill materials; the influence of variations in types, quantities, or sequences of availability of various fill materials;

and the relative merits of various sections and the influence of foundation condition. Although procedures for stability analyses (see EM 1110-2-1902

and Edris 1992) afford a convenient means for comparing various trial sections and the influence of foundation conditions, final selection of the type of embankment and final design of the embankment are based, to a large extent, upon experience and judgment.

d. Features of design.

Major features of design are required foundation treatment, abutment

stability, seepage conditions, stability of slopes adjacent to control structure approach channels and stilling basins, stability of reservoir slopes, and ability of the reservoir to retain the water stored. These features should be studied with reference to field conditions and to various alternatives before initiating detailed stability or seepage analyses.

e. Other considerations.

Other design considerations include the influence of climate, which governs the length of the construction season and affects decisions on the type of fill material to be used, the relationship of the width of the valley and its influence on river diversion and type of dam, the planned utilization

of the project (for example, whether the embankment will have a permanent pool or be used for short-term storage), the influence of valley configuration and topographic features on wave action and required slope protection, the

seismic activity of the area, and the effect of construction on the environment

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