Rock Final

Dam Construction: Materials

Large amounts of clay, sand and gravel (or concrete aggregate) are needed for dam construction.
If available, these materials will be collected as near to the site of the dam as possible.

-Poorly sorted, non-stratified moraine deposit
-Sorted, stratified outwash deposit (gravels and sand)

Earthquakes: Surface Waves

- Transmit energy along Earth's surface, causing the Earth's surface to vibrate

- Love Wave
- Rayleigh Waves

Chemical Weathering: Oxidation

-Reaction of free oxygen with metallic minerals
- Most affected rocks: Pyrite, pyrrhotite, Biotite, Amphibole, Pyroxene
-Causes coloration of rocks

Hydrologic Cycle

Precipitation, Infiltration, Runoff, Evaporation, Transpiration, Sublimation

Precipitation

Rain or snowfall on land or oceans

Infiltration (Percolation)

surface water soaks into the ground (fills cracks and pore spaces in soil or rock)

Runoff

the portion of precipitation (rain + snow) that DOES NOT infiltrate into the ground, but flows over the surface and eventually collects in streams, lakes, oceans

Evaporation

transformation of fluid form to gas form (water from open bodies of water become vapor in atmosphere)

Transpiration

Groundwater is absorbed into plant roots, carried up to the leaves and re-enters the atmosphere as water vapor

Evapotranspiration

Evaporation + Transpiration

Sublimation

snow or ice transform directly from solid form to gas form (water vapour) and return to the atmosphere

Water Balance

Flow in = Flow out
-Total flows between the various reservoirs
-approximately balance each other.

Dynamic Exchange

Groundwater

- water beneath earth's surface
- about 1/5 of all fresh water on Earth
- to use it source must be
1. Be economical to extract from subsurface
2. Satisfy certain criteria regarding quality

Water Table

- Ground is saturated below water table
- Roughly follows the topography of the landscape, changes seasonally

Groundwater Use

- Domestic use
- Irrigation
- Community water supply
- Pulp mills
- Mining
- Industrial processes

Where is Groundwater stored?

pores spaces and fractures of sediments and rocks

Groundwater Availability

Porosity, permeability, sustainability

Porosity (n)

- Defines how much void space is present per volume of rock/sediment
- If saturated with water, it defines how much water is present per unit volume of rock or sediment.

Typical Intergranular Porosity Values

•Sediments: loose sand, gravel, silt, clay (0.40

40%)
• Sandstone (

30%)
• Shales (

10%)
• Granite (<< 0.01

1%)

Permeability (k)

- Capacity of rock/soil to transmit water (or other fluids)
- How pore spaces in a porous medium are connected
- Depends on grain size distribution and connectivity of pores

Most permeable: sand, gravel, sandstone, limestone, fractured rock
Least permeable: silt, clay, shale, unfractured crystalline rock (ig,met)

-reflects ONLY the medium properties

-Influences
•size, shape, packing of grains,
•degree of cementation, and
•amount/nature of fracturing (especially rock)

Hydraulic Conductivity (K)

- the ability of a porous medium to transmit fluids

- includes properties of
the porous medium (e.g., permeability)
AND properties of the fluid (e.g., viscosity)

Hydraulic Head (h)

- a combined measure of pressure and elevation, relative to a specified datum (z=0) in an aquifer, and is expressed in units of length.

Hydraulic Gradient (i)

-Measure of the driving force for groundwater movement or flow (~slope)
- Water flows from High head to low head

Darcy's Law

-Empirical law of one‐dimensional flow in a fully saturated medium (sand used in experiments)
-Flux (flow) is the amount of fluid through a given cross-sectional area per unit of time
- q=Ki

q=flux
K= Hydraulic Conductivity
i = dh/dL Gradient

- Flow in a permeable medium is:
•directly proportional to hydraulic conductivity
•directly proportional to hydraulic gradient
•directly proportional to head difference
•inversely proportional to distance

What does Darcy's Law tell us?

-How much water can be pumped from an aquifer?
-How much water is leaking through a clay liner beneath a landfill?
-How much water will enter an excavation at a construction site?
-How much water will leak into a tunnel?
-How much water will leak through a dam?

Recharge Area

-Precipitation and infiltration
-Usually topographically high area
-Hydraulic head highest

Discharge Areas

-Areas where water seeps out of the ground as springs or enters rivers, lakes, or the ocean
- topographically low areas
- Hydraulic head lowest

Gaining Streams

-streams that gain water from groundwater discharge
-Streams that gain water from the inflow of groundwater through the streambed.

Losing Streams

The channel lies above the water table and loses water into the unsaturated zone.

Aquifers

- Transferring water
- Permeable layers of rock and sediment that contain groundwater in many small spaces.
- transmit significant amount of water
- can be tapped by wells for a water supply
- Confined, Unconfined, Perched
-Commonly sands, gravels, limestones, sandstones, basalts

Aquitards

-retards the movement of water
-geologic formation that can store water, but can transmit it only slowly
-cannot provide sufficient quantities to sustain pumping wells
- clays, shales, tight crystalline rocks

Unconfined Aquifers (water table aquifers)

- aquifers that are not confined by an overlying aquitard

Confined Aquifers

- confined below and above by aquitards

Artesian aquifer

-A confined aquifer containing groundwater under positive pressure
-a confined aquifer containing groundwater under pressure.
-flowing artesian wells

Perched Aquifer

-"puddle" of water atop a clay lens. Can be easily drained of water and cause a dry well
-an aquifer that rests on a layer of impermeable rock at a higher elevation

Cone of Depression

-cause the water table to decline locally and form a cone of depression.
-Water saturated pore space is drained
-Ceasing pumping, water table will rise to its original level
-The rate of recovery depends on both porosity and permeability of the aquifer

Groundwater extraction from a CONFINED aquifer

-saturation of pores remain unchanged
-fluid pressure reduced

Tides

Fluctuations in sea level caused by Earth's rotation, the gravitational effects of the Moon and Sun, and local topography and bathymetry

Storm Surge

General rise of water level caused by high wind and low atmospheric pressure

Seiche

Resonant oscillations in lakes/reservoirs (often following a storm surge)

Eustatic Sea Level Change

- Global sea level changes
- due to melting of glacier ice
- rate has increased recently due to global warming

Isostatic Sea Level Change

- Local sea level changes
- Due to loading or unloading of the crust (subsidence/uplift)
- uplift along the coast (Rebound due to unloading of glacier ice)

Tectonic Sea Level Change

- local sea level changes
- due to tectonic processes

Waves

- wind-generated waves
- travel downwind
- amplitude depends on wind speed, duration and fetch
- fetch: Distance over which the wind acts on the waves

Tsunamis

- Large displacement waves
- Can be generated by landslides, earthquakes, calving of glaciers and volcanic eruptions

Breakers

- a turbulent mass of agitated water rushing onshore
- release energy as
-heat: Mixed back into the ocean water
-motion: Sediments and rocks
-Reflects energy back to sea

Wave Breaks when...

-Steepness is too high
-Depth is too shallow

Wave Base

- the depth to which a passing wave causes significant water motion

Slope of the shore

- determines the type of breaker
- doesnt change daily

Wave At the Beach

- wave swash up the beach at a small angle
- backwash directly back to sea
- Due to refraction and reflection

Refraction

- wave approach the shore at an angle
- wave in shallow water slow and bunch up
- Wave in deep water continue and spread
- waves bend towards the shore

Longshore Current

- A flow vector parallel to the coastline due to wave refraction
- Can transport large volumes of sediment along the coast

Coastal Morphology: Erosional Features

- Wave-cut cliffs
- Wave-cut platforms
- Sea stacks
- Sea Arches
- Sea Caves

-Formed by longshore drift
(transportation of sediment by longshore current)

Coastal Morphology: Depositional Features

- spits
- Tombolos
- Barrier islands
- Tidal inlets
- Longshore bars

Longshore Drift

transportation of sediment by longshore current

Wave Rays

Lines Perpendicular to wave crests

Winter Beach

- Rough weather
- sand/longshore bar stored offshore

Summer Beach

- Calm weather
- Sand/longshore bar stored on the beach

Coastal Hazards

- Tropical storm: winds, rain, flooding (Cyclones, hurricanes, typhoons, monsoons
- Storm Surges (esp. at high tide)
- Tsunamis: Rapid displacements of water (Earthquakes, landslides, glacier calving, volcanic eruptions
- Sea Level Rise

Coastal Engineering

- Protection of property and infrastructure
-Erosion
-Inundation (flooding)
-Wave Energy
-Navigation
-Maintain water depth
-Shelter for vessel berthing, loading, storage

Five Generic Approaches to Coastal Management

1. Do nothing
2. Retreat
3. Hold the line
4. Advance
5. Limited Intervention

Coastal Engineering: Soft Solutions

-Beach Nourishment: add sediments, plants
-Dredging: remove sediments

Coastal Engineering: Hard Solutions

• Jetties - trap sediments
• Groynes (groins) - trap sediments
• Breakwaters - reflect or absorb wave energy
• Seawalls - reflect wave energy
• Revetments - absorb wave energy

Beach Nourishment

- add sediments

-Temporary (Eventually erode again)
-expensive
-commonly on popular (tourist beaches)

Dredging

-remove sediment

-temporary (eventually deposit again)
-expensive
-Commonly in major shipping channels

Jetties

- Structure perpendicular to shoreline
- Prevent blockage of inlet by longshore drift
- Designed to enhance and maintain navigation

Groynes

- Structures perpendicular to the shoreline
- Capture sediment transported by longshore drift
- Create/widen beaches and/or reduce shoreline erosion

Breakwaters

• Structures offshore &
parallel to the shoreline
• Break (block) incoming
waves before they reach
the shore
• Protect facilities
(marinas) or beaches
• Solid: reflect waves &
block sediment transport
• Porous: dissipate
waves & allow sediment
transport

-Used to protect harbours

Good: Protects boats from wave energy
Bad: Sediment build-up infills harbours

Sea Walls

• Vertical structures parallel to and along the shoreline
• Separate water from land
• Prevent erosion and damage due to wave action
• Reflect wave energy
• Sediments are stripped by waves
• Eventually erosion may undercut the wall

Revetments

• Sloping structures parallel to the shoreline
• Constructed to mimic natural slope of the shoreline profile
• Dissipate wave energy

Weathering

-Mechanical and/or chemical breakdown of rocks exposed at the Earth's surface into smaller particles
=that may differ in composition from the original substance
- Occurs in situ. with NO movement

Mechanical Weathering

Processes that split large rocks into smaller ones by exerting forces that exceed the strength of the rock.

Mechanical Weathering: Frost Wedging

-Water along fractures in rocks freezes, expands, and exceeds the tensile strength of the rock, causing it to split
- The volume of ice is ~9% more than water volume
• Frequent freeze thaw cycles
• Produces large angular blocks of rock called talus (scree)

Mechanical Weathering: Salt Wedging

- pressure created by crystallization of salt particles in pore spaces and along fractures
- As water evaporates, minerals are left behind to grow and exert pressure on the surrounding rock
-Common in coastal areas, arid climate, polluted air

Mechanical Weathering: Exfoliation (sheeting)

- Removal of overlying rock releases the elastic deformation and the rock expands.
- Commonly results in the formation of 'fractures' parallel to the ground surface

Mechanical Weathering: Root Wedging

- Tree roots grow in existing cracks
- relatively minor weathering force in rocks

Chemical Weathering

-Disintegration of rock-forming minerals by chemical reactions with water and/or atmospheric gases.
-Agents: Oxygen, Water, Minerals

-Rocks originate from deep inside Earth or without gases are unstable (rapid disintegration)

Chemical Weathering: Solution (Dissolution)

"Soft rocks" (evaporites, carbonates) dissolve, because their minerals react with water and acids

Chemical Weathering: Hydrolysis

-Over time, silicates such as feldspar react with the H+ ion in water and "breakdown"
-They produce clay minerals such as kaolinite and release ions such as K and Si that are removed in solution

What Aids in Mechanical/chemical Weathering of rocks and minerals?

• Faults/Fractures/Conduits
• Porosity of the rocks
• Increase of (exposed) surface area
• Climate (temperature, moisture)
• Composition of minerals

Effect of Temperature

1. Mechanical: freeze‐thaw effects
2. Thermal expansion
3.Chemical: rates increase with temperature
-Rule of thumb: chemical reactivity rates increase by a factor of 2 for every 10 degrees C

Best Climate to Avoid Weathering

Dry and hot

Acid Rock Drainage (ARD)

-Sulfide minerals undergo oxidation under atmospheric conditions

Manage Abandoned mine sites to minimize environmental impacts

-Cover waste rock piles and tailings
-Dry cover
-Wet cover
-Water cover
-Treat seepage prior to discharge to streams or lakes

ARD Treatment

- Limit exposure to atm
- Blend reactive rock with non-reactive rock
-Add alkaline materials such as lime to waste prior to deposition

Agents of Erosion

Gravity, wind, ice and water

Soil: A Geologist's Perspective

-Origins, depositional environment and tranportation agent
-Residual soils: no transportation
- Transported soils: accumulate after being eroded

Soil: Engineers' Perspectives

- Soil: Topsoil and subsoil
- Bedrock

-Anything that can be excavated by a shovel
-Particle size(texture)
- Particle-size distribution/gradation
-density
-shear strength
-Water content of soil

Soil: Soil Scientists' Perspectives

- interested in soil's ability to support plant life

Unified Soil Classification System

G- Gravel
S- Sand
M- Silt
C- Clay
O- Organic

Gradation

Sieve test

Soil Hazards

- Soil Liquefaction
- Subsidence due to dewatering
- Expansive (Swelling) Soils
- Soft soils
- Collapsible soils
- Sensitive Soils (Quick Clays)

Expansive Soils

- Most costly source of damage in N.A.
- soil contains a high proportion of swelling clays
- Only operates in the upper part of the soil profile (repeated wetting/drying)
-Expansive clay (water get into silicate structures)

Damage:
-Differential expansion to structural damage

Loam

A type of soil that is good for growing plants