GEOLOGY ENGINEERING

Geology, uses the scientific method to explain natural aspects of the earth, for example :How mountains form? How earthquake form?

Geology, benefits to everyone on this planet.Radio, clothes, car exist because of what geologists have discovered about earth.Mankind might have survived an earthquake, flood or other natural disaster because the scientists (geologists) have learned about these hazards.

Civil engineering works are all carried out on or in the ground. Ground properties & processes are therefore significant

To understand the principles of geology in civil engineering constructions AND avoid failures

Effect of geologic elements (rock, soils, landslides, earthquakes, groundwater) must be understood to ensure safety & sustainable development.

An engineering geologist is an individual who applies geologic data, principles, and interpretation so that geologic factors affecting the planning, design, construction, and maintenance of civil engineering works are properly recognized and utilized

(Geologist and Geophysicist Act 1986).

Site investigation is where civil engineers encounter geology. This involves the interpretation of ground conditions (often from minimal evidence), some 3-D thinking, & the recognition of areas of difficult ground or potential geohazards.

Earth visualised as a giant machine driven by two engines, both are Heat enginesExternalInternal

InternalDriven by heat moving from the hot interior of the earth toward the cooler exterior. Moving plates and earthquakes are products of this heat engine.

ExternalDriven by solar power. Heat from the Sun provides the energy for circulating the atmosphere and oceans. Water, especially from the ocean, evaporates because of solar heating.

Over long periods of time, moisture at the Earths surface hepls rock disintegrate.

Mountaions originally raised by Earths internal force (internal engine) are worn away by process of external engine.

The Earths internal heat engine works because hot, bouyant material deep within the earth moves slowly upward toward the cool surface and cold, denser material moves downward.

As the water immediately above the fire gets hotter, it expands, become less dense (weigh become less) and rises. Water at the top will loses heat to the air, cools, contracts, becomes denser and sinks.

The upper portion of the mantle is in contact with the relatively cool crust while the lower portion is in contact with the hot outer core. Obviously, a temperature gradient must exist within the mantle

The variation of mantle density with temperature produces the unstable situation of denser (cooler) material resting on top of less dense (warmer) material.

Eventually, the cooler, denser material begins to sink under the action of gravity and the warmer, less dense material begins to rise.

The sinking material gradually warms and becomes less dense; eventually, it will move laterally and begin to rise again as subsequently cooled material begins to sink. This process is the familiar one of convection.

Two major types of crust are Oceanic crust and Continental crust.

The crust under the ocean is much thinner. It is made of rock that is somewhat denser than the rock underlies the continents.

Uppermost part of the mantle are relatively rigid. This layer known as lithosphere. lith means rock in Greek.

Uppermost mantle underlying the lithosphere, called the asthenosphere, is soft and therefore flows more readily than the underlying mantle. It provides a lubricating layer over which the lithosphere moves (asthenos means weak in Greek)

Where hot mantle material wells upward, it will uplift the lithosphere. Where the lithosphere is coldest and densest, it will sink down through the asthenosphere and into the deeper mantle.

The forces generated inside the earth called as Tectonic Force, cause the deformation of rock as well as vertical and horizontal movement of portions of the earths crust.

Plate tectonics regards the lithosphere as broken plates that are in motion.

The plates, which are much like segments of the cracked shell on a boiled egg.

The theory that has come to be known as continental drift was not proposed until the early twentieth century (Taylor, 1910; Wegener, 1915).Wegener, for example, believed that the earth had only One large continent called Pangaea 200 million years ago. He believed that Pangaea broke into pieces that slowly drifted

The basic hypothesis of plate tectonics is that the earth's surface consists of a number of large, intact blocks called plates, and that these plates move with respect to each otherThere are three types of plate boundaries: divergent boundary, convergent boundary, and transform boundary.

The earth's crust is divided into six continental-sized plates (African, American, Antarctic, Australia-Indian, Eurasian, and Pacific) and about 14 of subcontinental size (e.g., Caribbean, Cocos, Nazca, Philippine, etc.).

Although most divergent boundaries present today are located within oceanic plates, a divergent boundary typically initiates within a continent.

It begin when a split, or rift in the continent or is caused either by extensional(stretching) forces within the continent or by upwelling of hot asthenosphere from the mantle below.

Either way, the continent plate pulls apart and thins. Initially, a narrow valley is formed. Fissures extend into magma chamber.

Magma (molten rock) flows into the fissures and may erupt onto the floor of the rift. With continued seperation, the valley deepens, the crust beneath the valley sinks, and a narrow sea floor is formed.

Underlying the new sea floor is rock that has been newly created by underwater eruptions and solidification of magma in fissures. Rock that form when magma solidifies is IGNEOUS ROCK.

The Igneous rock that solidifies on the sea floor and in fissures become oceanic crust.

By accommodating the addition of new sea floor at divergent boundaries, the destruction of old sea floor at convergent boundaries ensures the Earth does not grow in size.Platesmove toward each other

Convergent boundaries describe by the character of the plates that are involved: Ocean-continent, Ocean-ocean and Continent-continent.

Occurs where two plates slide horizontally past each other, rather than toward or away from each other.

A fault is a crack in the Earth's crust. Typically, faults are associated with, or form, the boundaries between Earth's tectonic plates.

In an active fault, the pieces of the Earth's crust along a fault move over time.

The moving rocks can cause earthquakes.

The main types of faults are

-Normal dip-slip fault-Reverse dip-slip fault-Transform (strike-slip) faults

Faults are fractures in the Earths surface along which displacement has occurredIf movement could take place continuously along faults then major earthquakes would not occur.

However, most faults become locked such that forces (movement of plate tectonics) causing the displacement continue to increase until the shear strength of the obstruction is exceeded, resulting in the sudden release of a significant amount of strain energy, causing the earthquake.

Tsunami, is preferred by geologist to represent the huge waves.

Tsunami also called as seismic sea waves.

The sudden movement of the sea floor upward or downward, during a submarine earthquake

A tsunami is generated in an ocean by a disturbance such as an earthquake, landslide, volcanic eruption, or meteorite impact.

Can be caused by large earthquakes, can also cause tsunami waves to form as water attempts to find a stable position.

Undersea earthquakes, which typically occur at boundaries between Earths tectonic plates, cause the water above to be moved up or down.

can create enough force to uplift the water column and generate a tsunami.

Asteroid impacts disturb the water from above, as momentum from falling debris is transferred to the water into which the debris falls.

Most tsunamis are caused by earthquakes generated in asubduction zone, an area where an oceanic plate is being forced down into the mantle byplate tectonicforces.

The friction between the subducting plate and the overriding plate is enormous. This friction prevents a slow and steady rate of subduction and instead the two plates become "stuck".

Stuck causes a slow distortion of the overriding plate. The result is an accumulation of energy very similar to the energy stored in a compressed spring.

Energy can accumulate in the overriding plate over a long period of time - decades or even centuries

Energy accumulates in the overriding plate until it exceeds the frictional forces between the two stuck plates. When this happens, the overriding plate snaps back into an unrestrained position

This sudden motion is the cause of the tsunami - because it gives an enormous shove to the overlying water. At the same time, inland areas of the overriding plate are suddenly lowered.

The moving wave begins travelling out from where the earthquake has occurred.

Some of the water travels out and across the ocean basin, and, at the same time, water rushes landward to flood the recently lowered shoreline

Liquefaction is a condition in which soils, typically loose saturated sands and silty sands, behave as a fluid

This is a result of strong vibration and is normally related to moderate to large earthquakesWhen liquefaction occurs the shear strength of the soil is reduced essentially to zero.

As a result, the soil will no longer be able to support the foundations for buildings and bridges.

Bearing capacity failure: an apartment block that has toppled over due to bearing capacity failure resulting from liquefaction.