Engineering Geology Flashcards
Types of building and construction materials - Building stone
Must be - Competent, well jointed, attractive, impermeable and resistant
Types of building and construction materials - Aggregate
Natural aggregate is sand and gravel mainly extracted from recent quaternary river, must be clean with no impurities
Crushed rock aggregate - mainly for roadstone
Types of building and construction materials - Roadstone
Must be - Strong and high impact and crushing strength, resistant to abrasion and mechanical weathering, Impermeable and resistant chemical corrosion
Skid resistant - Each chipping must be made of more than one mineral with different hardness, and bond with bitumen well
Types of building and construction materials - Brick clay
Thick beds with constant composition are required
Geological conditions affecting the construction of dams and reservoirs - general conditions
A lack of seismic and volcanic activity in the area
Valley sides need to be stable so mass movement is unlikely
The river catchment needs to have sufficient rainfall and be underlain by impermeable rocks to promote surface runoff for collection in the reservoir
Geological conditions affecting the construction of dams and reservoirs - Foundations
Strong and competent with a high load-bearing strength too support the combined weight of the dam
Impermeable to prevent leakage
Ground improvement methods to prevent leakage from reservoirs
Grouting - holes are drilled into the rock and liquid cement pumped in. The cement fills pore spaces, joints and fissures, reducing permeability and increasing rock strength
Clay or pore lining - Reservoir is lined with impermeable material such as clay or plastic
Cut off curtain - Impermeable barrier, usually made of concrete, constructed as an extension below the dam
Ground improvement strategies used to stabilise slopes and rocks
Slope modification - Slope is reduced to a lower angle
Gabion - Wire mesh boxes filled with rocks and placed as lateral toe support at the bottom of slopes to prevent failure by slumping
Rock bolt - Steel rods several meters long are drilled and cemented into rock faces to prevent rock falls
Rock drains - Addition of water is a common cause of slope failure, so drains of broken rock can be constructed, this removed pore fluid pressure
Wire netting - This will fix surfaces in place and catch small rock falls
Shotcrete - Concrete is sprayed at high pressure onto rock surfaces, this increases strength and protects from weathering
Vegetation - Plants fix soil in place and reduce infiltration of water
Strategies to reduce coastal erosion and flooding - Sea walls and banks
Protect from erosion swell as flooding
Can be vertical or curved to reflect wave energy effective in short term but not long term
Strategies to reduce coastal erosion and flooding - Rock buttresses, revetments and rip rap
Cheap way of protecting against coastal erosion, large blocks are piled up to reduce wave action
Strategies to reduce coastal erosion and flooding - Groynes
Reduce sediment loss from LSD
Strategies to reduce coastal erosion and flooding - Bech nourishment
Soft engineering, very popular, import sand used to build up beaches
Geological factors affecting landfill sites - Rock type
Fine grained impermeable such as clay is most suitable for landfill sites
Geological factors affecting landfill sites - Geological structures and attitude of the strata
Faults increase the permeability of rocks and provide escape routes for leachate
Joints in rocks such as limestone also allow downward leakage of leachates
Tilted or folded beds allow down-dip from the landfill site through permeable beds
Anticlines may have tension joints at their crests
Geological factors affecting landfill sites - Groundwater
If the water table is high then there is less distance for the leachate to travel to reach underlying ground water
