Engineering Geology (Introduction)

Engineering geology is the application of the geological sciences to engineering study for the purpose of assuring that the geological factors regarding the location, design, construction, operation and maintenance of engineering works are recognized and accounted for.

What’s the purpose of Engineering Geology on Engineering students?

Geology provides a systematic knowledge of construction material, its occurrence, composition, durability and other properties. Example of such construction materials is building stones, road metal, clay, limestones and laterite.

The knowledge of the geological work of natural agencies such as water, wind, ice and earthquakes helps in planning and 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 harbour work and soil conservation.

Ground water is the water which occurs in the 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.

In the study of soil mechanics, it is necessary to know how the soil materials are formed in nature.

The cost of engineering works will considerably reduced of the geological survey of the area concerned is done before hand.

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 drilling data.

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 very necessary.

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 the projects.

The stability of civil engineering structure is considerably increased if the geological feature like faults, joints, bedding planes, folding solution channels etc. in the rock beds are properly located and suitably treated.

Earth’s Size & Shape

I. Model

A representation of an object, a process, or a phenomenon.Ex.– Globe – best, most to scale model

of the Earth– Computer Climate

models/Simulations

Part of the Universe that can be studied separately

– Closed System- a system in which energy can enter or leave, but matter cannot

– Open System- a system in which there is a free exchange of both energy & matter between the system & its surroundings.

II. A System

The Structure of the Earth

Structure of the Earth

The Earth is made up of 3 main layers:– Core– Mantle– Crust

Inner core

Outer core

Mantle

Crust

The Crust

This is where we live.

The Earth’s crust is made of:

Continental Crust

- thick (10-70km)

- buoyant (less dense than oceanic

crust)

- mostly old

Oceanic Crust

- thin (~7 km)

- dense (sinks under continental crust)

- young

III. Structure of the Earth

A. Inner Core - layer of the Earth composed of solid iron & nickel

B. Outer Core - layer of the Earth composed of liquid iron & nickel

Structure of the Earth Cont’

C. Mantle - largest Earth layer composed of silicon, oxygen,

magnesium, & ironD. Crust - outer most layer of Earth

the deepest mines & caves go no further than the crust

thicker under the continents than the ocean

Layers of the Earth

IV.Temperatures Below the Surface

Deep caves stay about the same temperature all year

From 0 m to 20 m below, a cave usually remains equal to the avg. yearly temperature

Every 40 m below the 1st 20 m, the temperature in a cave 10C for each 40 m (120ft)

Heat is from:

Radioactive Minerals– Ex Uranium & Thorium

Compression of the crust by gravity

V. Earth’s Shape

A. Evidence that Earth is Spherical

1. The mast of a ship is the 1st part to appear over the horizon & the last to disappear.

Earth From Space

2. Photographs of Earth from space

Earth’s Shape Cont’

3. An eclipse of the moon occurs when Earth's shadow falls on the moon

The shadow is always an arc of a circle

http://www.rit.edu/~andpph/eclipse-01-20-00.htm l

4. Ships sailing north or south observed changes in the nighttime sky.

North Star appears higher in the sky as a ship travels north

Ships sailing south lose sight of the Big Dipper & begin to see the Southern Cross

Earth’s Shape Cont’

B. Oblate Spheroid

Sphere that is slightly flattened at the poles & bulged at the equator

Caused by Earth's rotation

C. Weight on Earth

VI. Earth’s Density

A. Density – The amount of matter (mass) in a given space (volume)

Average density = 5.5 g/cm3

VII. Measuring Earth's Circumference

A. Eratosthenes (er uh Tos thuh neez)

Of Greek heritage, born in Cyrene, now

Shah hat, (Libya) Studied at Alexandria & Athens Appointed Director of the Alexandrian

Library, 236 BC

Eratosthenes Cont’

Lived in Egypt1st Scientific Measurement of Earth’s

CircumferenceWent blind 195 BC Starved himself to death 194 BC

Facts Eratosthenes knew:

At noon on June 21st (Summer solstice):

The sun casts a shadow of 7.2o from an obelisk in Alexandria

The sun cast no shadow in a well in Syene (called Aswan today)

Facts Eratosthenes knew:

Believed the suns rays hit the Earth as parallel lines

Eratosthenes figured Syene was due south of Alexandria (He was slightly off on this one)

Distance between Syene & Alexandria (925km) slightly off

Thought both cities were on the same line of longitude (off on this by 30)

VIII. Types of Data

Qualitative – data that is relative but not numeric. – Ex. The color of an object or stating

someone is tall or taller than another person

Quantitative – data where a numeric measurement or a count of objects has been made

IX. 4 Spheres/Subdivisions of Earth

1. Atmosphere

2. Geosphere

3. Hydrosphere

4. Biosphere

1. Atmosphere

Atmos- Greek, Meaning vapor– Ozone- O3, protects Earth from Sun’s

harmful UV rays– Oxygen & Carbon Dioxide provided for

living things– Water vapor forms

clouds

2. Geosphere

Geo –Greek, meaning Earth– Rocks, Mountains, Beaches

3. Hydrosphere

Hydro- Greek meaning water– All the water of the Earth’s System

OceansGlaciersGroundwaterRiversLakes

4. Biosphere

Bio- Greek meaning Life– All forms of life on Earth from microscopic

to Human