Geology for Civil Engineering

Introduction to Geology in Engineering

• Geology, also known as earth science, is derived from the Greek words "geo" (Earth) and "logos" (Science).
• Explores Earth's formation, structure, composition, and the natural processes acting upon it.
• Integrates the 4.5 billion-year history of Earth.
• The thorough examination of a structure's surroundings, especially foundation materials, should precede design.
• Focuses on safe, economical designs that consider Earth's structure and features essential to civil engineering.
• Engineers use this geological data during the planning, designing, and construction phases of civil engineering projects.

Relevance of Geology in Civil Engineering

• Geological site investigations are conducted before construction to prevent unexpected disasters
• Understanding subsurface is critical to ensure stability and safetly
• Geological hazards like earthquakes, landslides, and sinkholes must be evaluated to prevent structural failures.
• Engineering geologists analyze data, soil composition, and seismic activity to assess risks and implement precautions.
• Identifying soil load-bearing capacities is important

Foundation Design and Slope Stability

• Foundation design and slope stability are important factors in determining long-term durability.
• Geological studies aid engineers in designing foundation based on soil and rock characteristics.
• Understanding how soils respond to weight and measure is essential in choosing foundation types.
• Natural slopes can become unstable due to rain, seismic activity of human actions.
• Ground improvement techniques like compaction, gouting, and geotextiles are used when the ground is weak

Material Selection and Resource Evaluation

• Geology provides ways to obtain building materials
• Identifying suitable building materials from rock and minerals are used in construction depending on material properties.
• Granite is used for countertops, while basalt is ideal for road construction due to its strength.
• Durability determined based on environmental factors.
• Coastal buildings require salt-resistant materials.

Tunneling and Underground Construction

• Ensure structural integrity of tunnels, which require understanding geology.
• Rock mechanics and support design ensure the best support systems are in place.
• Uncontrolled groundwater can flood tunnels, so engineers use pumps and trenches to manage this.
• Environmental and hazard mitigation are important during construction.
• Use of techniques to stabilise slopes and prevent soil erosion.

Cost Reduction and Project Sustainability

• Incorporate geological insights to lower costs on geological engineering projects.
• Cost reduction is achieved by preventing construction delays, optimising design and materials and enhancing sustainability.
• Early identification of geological challenges allows for informed planning.
• Geological assessments ensures the efficient use of materials.
• By understanding and mitigating geological risks, structures are designed to be more durable.

Branches of Geology

• Geology studies Earth's composition, structure, processes, and history.

Physical Geology

• Studies Earth's surface features like mountains, valleys, rivers, lakes, glaciers, and volcanoes.
• Examines changes like marine transgression and regression, along with natural events like landslides, earthquakes, and weathering.
• Crucial for site selection, risk assessment, and designing structures to withstand geological forces.

Crystallography

• Studies crystals solid materials with a regular polyhedral structure.
• Essential for mineral identification in construction.
• External shape of crystal, aka habit, influenced by atomic arrangement
• Habit affected by space, temperature, pressure, and chemical composition.

Mineralogy

• Study composition, structure, and properties of mineral.
• Mineral compotisition essentiel for construction materials.
• Engineers analyze mineral stability to assess structure building durability.
• Identifying harmful minerals, such as expansive clays or pyrite, helps prevent structural failures.

Petrology

• Petrology, the study of rocks and their formation processes in vital in building
• Helps in determining suitable foundation materials
• igneous, sedimentary, and metamorphic rocks help engineers evaluate rock strength, permeability, and weathering resistance.
• Allows the design of stable structures, bridges and tunnels

Structural Geology

• AKA Tectonic geology
• Studies rocks formed by tectonic plates
• Helps select suitable sites for consturction zones
• Aids in accessing rock formations to reduce risk

Stratigraphy

• Studies rocks and correlations to gain climate insight
• Also know as historical geology to understand earths history
• Civil engineering essential for site anaylsis for construction

Paleontology

• Study of fossil and past lifeform
• Contribute insights into geological history of an area
• Fossils aid in determining soil and layers of rock

Economic Geology

• Studies of mineral, rock, and econommic significance
• Resource is essential for industries and consturction
• Helps select appropriate material and resrource planning for project development

Mining Geology

• Applies principles to locate and acquire material
• For selecting quarrying and material to make resources
• Crucial for infrastructure material and resourcing

Civil Engineering Geology

• Apply the principle to project
• Involves site investigation and analyisis to make slope safety
• Assessment to prevent failures due to weak bedrock

Hydrology

• Studies the movements and properties of water
• Crucial for designing drainage systemd
• Analysis on groundwater and aquifer characateritics

Photo geology involves the use of aerial photographs and satellite imagery to analyze geological features.

• Aids in terrain building
• Helps asses land
• Helps monitor geologicalhazards

Earth Structure and Composition

• Earth is divided into three main layers: the crust, the mantle, and the core.

Crust

• The outermost part and thinnest layer of the Earth.
• Makes up less than 1% of planet's mass.
• Divided into continental and oceanic crust.
• Continental crust is rich in slica and alium, which makes it also called the SIAL Layer and it's thicker
• Oceanic Crust is thinner than continental crust, made of silica, magnesi, and made of SIMA Layer
• It separates the crush from the upper mantle.
• It separates the crush from the upper mantle.
• Discovered in 1909 by Andrija Mohorovicic.

Composition of the Crust

• 98.5% of Earth's crust is composed of eight elements
• Top 2 elements are are Oxtgen (46.6%) and Silicon (27.7%)
• Total crust volume is 93%

Mantle

• The solid rock layer between earth and core
• It extends to a depth of 2885km and consists of 68%mass
• Located when most internal heat of Earth is
• Movement of material causes convection currents
• Main made of peritote, which is denser than basalt and granite
• Lithosphere 70-100km
  • Layer that includes portion of mantle
• Asthenosphere 100-350km
  • Upper layer
  • Low seismic zone
• Upper mantle
  • Primarily composed of olivine and pyroxene
• Lower mantle
  • silicon, magnesium, and oxygen with smaller amounts of iron

Core

• Makes up 31% of Earth's mass
• Mostly made of iron and lighter elements
• Two layers
• Outer core
  • liquid iron and nickel with sulfur and oxygen amounts
  • Generates planet magnetic field
• Inter core
  • Primarily of iron and nickel
  • Still solid though because of pressure

Continental Drift Theory

• A german geophysicist spotted something odd on the map in 1912.
• The continents of Africa and South America appeared to fit together quite well if the Atlantic Ocean were removed.
• Fossils were discovered on divided continents that were similar and provide more evidence.
• Pangaea meaning all lands, was a landmass supercontinent and exsisted before the plates split it 250 - 220 million years ago

Continental Drift terminologies

• Continental drift are movements of continents
• Alfred Wegener supported his theory with maps and evidence
• Pangea is a supercontinent broken a part
• Panthalassa is the water surrounding Pangea
• Laurasia vs. Gondwanaland are two continent masses
• Evidences are supported by rock, fossils, an climate

Plate Tectonics

• Pangea and Laurasia split
• Wegener expanded concept original hypothesis
• Earths produce significant land form -outermost layer known outermost rocky plates divided which is the lithosphere which sit partially on the Asthenosphere ,semi molten layer
• Plates relative and speeds causes distinct geo-features
• Numerous distinct geological structures exist on the East African Rift , California's San Andreas Fault, and Himalayan mountain range.
• Earthquakes happen due to movement alogn zone plate bounaries
• The structure and movements shape Earth

Types of Plate Tectonic Boundaries

• Divergent boundaries, plates move apart and earthquakes are frequent
• Mid-Atlantic Ridge are created when Earth molten layer rises to the surface to form oceanic crusts
• Convergent boundary the edges may collapse on a seafloor or collapse into mountain edges
• Meltin creates chain of volcanos
• Pacific ring strong is a convertgent plate
• At the undersea San Andreas fault a transform plate slide past each other. When transform, natural, or man-made structures are offset or broken

Weathering

• Weathering is the natural process of breaking down rocks at Earth's surface through environmental factors like rainwater, temperature fluctuations, and biological activity, unlike erosion which transport

• Three main types

  • Physical
    • Physical weathering happens for temp changes with force
    • Types include thaw freeze
  • Chemical
    • Chemical weathering happens with rain water and minerals to make salts
    • Common in water bound region
    • Types: Solution, Hydrolysis, and oxidation
  • Biological
    • Biological weathering happens within living organisms breaking rock

• Process that occurs with

  • Root petration
  • Burrowing animals

Rivers

• Engineers concern is water flow, while geological perspective focus transporting surface
• River start at the head which ends at the mouth which slopes for material to carru
• Playfairs explain the formation of deep valleys by Eroion, tranportation, and deposition
• Erosion, a function of rivers, is when the turbulence cause the river shape

1. Attrition Causing particles rub to break each other down

2. Corrosion Water dissolves material which carry through solution

3. Abasion Physically scraping riverbeds occurs

4. Hydraulic Action Flowing rivers get dislodged materials

• River transport through three ways such as dissolve and suspendin three ways: 1. Dissolved load

2. Suspended load: Fine particles stay and settle on the riverbed moving by jumps or roll

• For Deposition, when water is slow particiles settle

• Largest deposits near the source, with the size decreasing as the water nears it

• These shape the rivers through

  • River Deepening
  • River Shortning
  • River WIdeining

River Stages

• Youth Stage (Upper course): this stage has Vertical erosion and characteristics shapes like V valleys
• Maturity Stage (Middle course): gentle gradient, features like flood plines
• The river bends into Meander.
• Old Age (Lower course): Last stages is Delta and has smooth and gentleness

Wind

• Wind plays an important role as it erodes, transports and helps deposit
• This all is called Easion work defilation:
• process of lifting a surface
• notable for forationa of Oases to make groundwater

Abrasion: Abrasion wears and striks rocks leading to uniques structure in deserts , creating dust storms , which carry and deposit and can obstrucr roads and bulidng

Sand Dunes: Wind deoposit to change winds location 4 type: crescent, rid, ridge

• Types of sand dunes:
  • Shore Lines
  • Riverbed
  • Desert:

Loess Deposits: fine grains found on wind , can be prone to engineer problems

• Can collapse when wet, as it will damage structure

Structural Stability, Soil Management, Infrastructure Planning

• Structures will require design to wind withstand loads
• Techniques that mitigate soll erosion and damage
• Highway, railways and can consider shifing and solutions

The sea and oceans cover 70% of Earth

• Seas the sea depth is generally less than 4 KM
  • seas get energy from dissipation along coastal and get wavelength when at rest
• Processes in seas
  • Erosion rock gradual breaks and waves, and water moves sand
• This effect lead coasts

1. Abrasion
2. Hydraulic Action
3. Attrition
4. Solution

Effects of Coast

• Creates material accumaltion that builds beaches
• The Deposition effect shapes and gives beach spits or long sand sea
• Can leave behind a water body known as a lagoon

Seismics

• Earthquake, hazard, and resource groundwater and water supply

1. There can be Seismic causes fluctuation when earthquake wells
2. There can be quality increase when earthquake occure, as in increase the shaking to contaiminate the water.
3. Aquifers can trigger and creat new shift by causing geological layer change
4. Can impact ground