Geotechnical engineering

name some examples of problems with ground conditions

Slope instability

Changing state

Dispersion of soils/rocks in water

Dissolution of salts in soils/rocks

Voids within rocks/soil

Chemically aggressive ground conditions

how to solve the problem of soft ground?

develop foundation design to reduce or redistribute loading

how to solve the problem of weak ground or presence of voids?

ground improvement techniques, identify and avoid hazards zone

how to solve the problem of unstable slopes and potential failure?

change slope angles, provide slope support, identify and avoid hazadous locations

how to solve the problem of river/coastal erosion?

slow processes down with rock or concrete defences

how to solve the problem of potential earthquake zones?

structural design to withstand vibrations, avoid unstable ground

how to solve the problem of potential volcanic hazards?

avoid hazard zone, attempt to predict eruption

name the three best known classification systems

Rock structure rating systems (RSR)

Geomechanics classification

Rock mass rating

geology

study of the earth

What does geology deal with?

The Earth’s physical structure and substance

HIstory

Processes that act on it

give a brief description on the structure of the Earth

The planet is in a constant state of change

Geological and geomorphological processes continually modify and change the Earth’s surface

List some examples of processes that tend to be cyclic

Rock/soil formation

weathering/deterioration

Destruction

New rocks formed

What lengths of time does the geological time scale work on?

the earth is approximately 4.5 billion years old, and geological process take time to occur

geological time is a very different concept to that which we are comfortable with

How do plate tectonics work?

Heat from the core radiates out into the mantle

this is not uniform in nature and results in convection currents within the mantle, causing Earth’s crust to move

movement of the plates results in a relative change in position of the land masses over time

Subduction

Oceanic and continental plates being driven into each other can result in the denser one being forced under one another

when does volcanic activity occur?

when molten magma breaches the ground surface to form lava; which cools to form new rocks

the chemistry of the lava dictates how it emanates from the volcano along with the properties of the newly formed rock

what’s the difference between mafic and felsic lava?

Mafic lava is rich in iron minerals and normally results in extruded flow

Felsic lava is rich in silicates and normally results in more explosive eruptions with rapid escape of previously trapped gases

does volcanic normmally result in single volcanoes?

No, it can cover significant tracts of land

why can faults encountered on site prove to be problematic?

Geology on either side of the fault can vary significantly

The faults themselves can also be planes of weakness e.g. act as preferential flow pathways

How can faults vary in size?

they can range from the small scale with microcracks to the large scale where failure planes extend for many kilometres

what do the variable properties of rock depend on?

Properties of the mineral constituents

Interlocking and weaknesses in the mineral structure

Fracture bedding and larger rock structure

what are the three types of rock?

Igneous

sedimentary

metamorphic

What are the characteristics of igneous rock?

Crystallised from molten magma

found both above and below ground

interlocking crystals

mostly massive

high strength

What are the characteristics of sedimentary rock?

Erosional debris on Earth’s surface

Found in terrestrial and marine depositional basins

granular, cemented

layered, highly structured formation

normally low strength

What are the characteristics of metamorphc rock?

Altered by heat and pressure

mainly found deep underground

interlocking crystals

Aligned structures

Normally high strength

Name some examples of igneous rock

basalt, granite

Name some examples of sedimentary rock

Sandstone, limestone, siltstone

Name some examples of metamorphic rock

Schist, gneiss, slate, marble

What types of rock is the UK home to?

LITERALLY EVERYTHING

The UK has a large variety of different rock types and projects can often be built across multiple types of rock

What are the different types of igneous rock?

Pyroclastic

extrusive igneous

intrusive igneous