Lecture 10: CE Applications Flashcards
CE applications of Geology
• Foundation • Excavation • Tunnelling • Dams and Reservoirs • Construction Materials • Slope Stability (Discussed in Geol Hazards as application and hazard)
COARSE GRAINED SOIL
– it means that majority of its particles are
bigger or on the coarser range of soil sizes
FINE GRAINED SOIL
– majority of the particles are on the finer side
COHESIONLESS SOIL
it means that the soil does not “stick”
together and cannot oppose pulling forces (think sand, if you try
to pull sand apart, there is no resistance and it just pulls apart)
COHESIVE SOIL
it means that the soil can oppose pulling forces
think clay, you can try to pull apart clay but it has resistance
The bottom part of a structure that serves to transfer the load of the structure to the Earth
Foundation
The soil/rock directly beneath the
foundation
Foundation Bed
The goal of a foundation
to transfer the load safely to the ground (ground does not give or collapse) and without too much
deformation (too much deformation means that the
purpose of the structure is no longer served efficiently)
2 limits in Designing Foundation
1 Strength Limit
2 Serviceability Limit
the limit when one part breaks due to
too much load.
Strength Limit
the limit related to the function
or useability of an object.
Serviceability Limit
For foundations, the relative parameters for strength limit and serviceability limits are
1 Foundation Capacity
2 Settlement
the maximum load that the foundation, based on its dimensions and soil supporting it, can carry
FOUNDATION CAPACITY
the amount of “sinking” that will happen to a
foundation (and hence the structure) once the loads of the structure are in place.
SETTLEMENT
2 Types of Settlement
1 Typical
2 Differential
settlement is the same for all points
of structure, hence the structure simply “sinks”.
Typical Settlement
settlement is different for different points of the structure, hence it may seem to “sink” and “rotate” at the same time.
Differential Settlement
Settlement that can lead to distortion damages to the structure
Differential
Settlement is not much of a limiting value when the foundation sits on_________
Rock
2 Parts of Settlement Foundation
1 Immediate
2 Consolidation
settlement that happens while
it is being constructed or immediately after
Immediate
settlement that happens over a long period of time. Way after the structure has been constructed, settlement still happens. This happens due to clays not allowing water to be expelled quickly, hence, it loses water over time, and as it does, it settles more.
Consolidation
DENSELY packed soils will allow __________ to happen compared to loosely packed soils.
less settlement
Is the ability of cay soils to hold water a good or a bad thing?
this is bad since it can take years before the building is able to force the water out in between clay minerals and this will result to settlement of clay over a long
period of time. This means that if your building is on clay, after a few years, you will find your building still sinking into the ground.
Why is long-time sinking a problem?
Because this is hard to remedy, compared to settlement that will be seen as you construct the
structure.
SHALLOW FOUNDATION
- Isolated Spread Footings
- Wall Footings
- Combined Footings
- Strap or Cantilevered Footings*
- Mat Foundation*
DEEP FOUNDATION
- Pile Foundation
- Driven Piles
- Bored Piles
- Pier/ Caisson Foundation
Foundations usually formed at shallow depths
Shallow Foundation
Shallow foundation is used when
- Material near the surface is strong enough for the structure
- While soil and rocks usually tend to be denser and stronger the deeper you go, this is not always the case. As such, it must be made sure that layers underneath the foundation bed are not weak as well.
1 footing for each column
Isolated Foundation
Continuous strip of footing supporting a wall of the structure.
Wall Footing
Footings with more than 1 column on them
Combined Footing
3 kinds of combined footings
(1) Rectangular
(2) Trapezoidal
(3) Strap/Cantilevered
2 separate spread footings and
then joined together by a strap beam
Strap footing
used to connect an eccentrically loaded
footing (footing where the load from the column is not located at the center of the footing) to another footing
Can also address differential Settlement
Strap Footing
Large foundation supporting more than 1 line of columns
Mat Footing
When is mat footing used?
Usually used when the soil is too weak but using (the more expensive) pile foundations proves to be uneconomical.
Used when the top layers are too weak to support the structure
Pile footing
2 types of Pile Footing
1 Driven
2 Bored
2 Ways Piles carries load
1 Skin Friction - friction on its sides
2 End Bearing Capacity -transferring the load on the other end
Situations encountered during rock excavation
- There are rocks that are solid and can be cut without much problem of instability
- There are rocks that crumble or weaken greatly when exposed to the elements
- There are rocks with naturally occurring weakness planes that make them safe or unsafe depending on how they are excavated and cut.
Ways of Excavating Rocks
- DRILLING
- BLASTING
- RIPPING
- DIGGING
Drilling of hard rocks are affected by
Rock hardness, abrasiveness, grain size, rock discontinuities
using explosives, put in blastholes, to break up rocks
Blasting
Factors that affect blast spacing
- ROCK STRENGTH – the stronger the rock, the closer the blastholes may need to be.
- ROCK DENSITY – the denser the rock, the closer the blastholes as well.
- ROCK’S FRACTURE PATTERN – blasting needs to be done such that the weaknesses are exploited, such that minimal blast strength will be needed.
Coditions that makes blasting harder
- ROCKS WITH HIGH SPECIFIC GRAVITY AND INTERGRANULAR COHESION (ex. Gabbro, Breccia, etc.)
- ROCKS THAT ARE BRITTLE BUT LOW RESISTANCE TO DYNAMIC STRESS (ex. Certain granites, marbles, etc.)
- ROCKS WITH PREFERRED ORIENTATION/WEAKNESS PLANES (ex. Mica schist)
This is a process where drilling and blasting is used to make a shear surface (or weakness) in a rock.
Pre-Splitting
This is breaking the rocks just enough so that they can be loaded to trucks, etc.
Ripping
Factors that affect ripping
- Rock’s intact strength (strength before it is ripped/broken into pieces)
- Fracture index
- Abrasiveness
Factors that affect digging
- ground’s intact strength
- Water content
- Bulk density and bulk factor
When excavation requires vertical face or side a ________ is used
support structure
2 Types of Excavation Support
BRACED SYSTEM
SHEET PILE
system that uses bracing in the excavation to
support the excavated walls. The braces may run from one side to the other of the excavation.
Braced System
system where the supporting wall is embedded
deep enough so that it can support the excavated wall and prevent it from caving into the hole
Sheet Pile
transfer the force of the soil from one side (trying to push into the hole) to the other side – such that the walls trying to cave in are stopping each other from doing so
Internal Braces
Supporting structures that are embedded deep enough, hence not needing supports like wales and struts
Sheet Piles
defines the form and kind of tunnel, as well as the cost
Geology
Various ways used to study the geology
- Pits
- Drilling
- Pilot Tunnels
Best way to study the geology and is usually
reserved for major tunnels and the site is suspected to have major geological issues/features relevant to the tunneling.
Pilot Tunnels
Geologic factors for determining the axis of the tunnel:
- Rock jointing
- Beds
- Dip angle and Strike
- Weathering
What do faults indicate with relation to the pressure on the rocks
Faults means there is non-uniform pressures in the rocks
rocks are released with explosive force
Rock Bursting
similar to rock bursting but is basically a milder form
where the sides bulge before breaking
Popping
These are giant machines that tunnel through rock and soil and create the tunnel support system as they go along as well.
Tunnel Boring Machine
amount of time the
rock mass can remain stable unsupported
Bridging Capacity
For tunnels done via drilling or blasting, support systems may include:
- Rock Bolts
- Shotcrete
- SteelArches
special “bolts” that attaches the sides of a tunnel to the
material behind it. Shown below are rock bolts as seen from inside the tunnel
and a 3D model of it
Rock Bolts
concrete shot at the sides to be the lining and provide
support. It can be used with rock bolts and reinforcing mesh as shown.
Shotcrete
arches to hold the tunnel shape much like how arches may support the interior of any structure. This is usually done as an extreme
measure for the weak segments of tunnels.
Steel Arches
Structure that traps/stops water from flowing further.
Dam
The body of water that the dam controls
Reservoir
Primary purpose of Reservoirs
Control water supply to:
• Ensure that there will be enough water supply at any time for the community it serves.
• Make sure the river it connects to never overflows.
Always located at the front of a reservoir
Dam
Located at the sides of a reservoir
Higher landforms
Factors affecting reservoir
- Dam location
- Water transport
- Reservoir’s water permeability
- Stability of reservoir sides
- Sedimentation
- Water Quality
- Possible Earthquake Effects
water flowing on land surface from rains, snow melts, etc.
Runoff
dictates the water transport/run-off characteristics
Topography
For dams, it is important that the location can
carry/support the
forces that the dam will carry and pass on to the ground or sides of
a mountain.
Dams may fail in several ways, but some of the simplest are by:
- Sliding
- Foundation Failure
- Overturning
Happens when the Force from water > “Friction” from ground
Sliding
The dam’s weight is too much for the ground to
hold
Foundation Failure
The forces are located such that the dam is
lifted at its upstream end and overturns/tips about the toe. (imagine your feet is a dam, and you are falling forward, hence the heel and toe of a dam)
Overturning
Kinds of Dams
Gravity dam, earth dam
Relies on weight of the dam to keep it stable (heavier dam is harder to slide and overturn).Typically made of reinforced concrete
Gravity Dam
Dam made of soil
Earth Dam
impermeable core of Earth dam
Clay
Earth Dams have mild slopes to
prevent the slopes from
failing
an example of arch-gravity dam it is a gravity dam that exploits the arches as well as additional support on its sides.
Hoover Dam
Rocks that are cut to desired sizes for decoration or for building purposes.
Dimension Stone
Sources of dimension stone
Granite, Limestone, MArble
Usually used as walls, roof materials, countertops, etc.
Dimension stone
Blocks of rock (may be single or collection of widely-graded rocks like riprap) that protect structures
Armorstone
Crushed rock that is used for concrete making.
Aggregates
Materials to create Cement
Limestone, silica, Alumina, and Iron
The ingredients of cement are ground and heated in the _________ to produce ______. The _________ is further grounded with additives such as ________ resulting in cement.
Rotary Kiln, Clinker, Clinker, Gypsum
• DAO NO. 2000-28
orders that, aside from the requirements to get
an Environment Compliance Certificate, an additional
ENGINEERING GEOLOGICAL AND GEOHAZARD ASSESSMENT is to be done.
EGGAR
ENGINEERING GEOLOGICAL AND
GEOHAZARD ASSESSMENT REPORT
EGGAR is accomplished by a
Geologist/ Engineer
EGGAR contents
- General information about the project
- Regional setting information
- Site geology that includes topography, hydrology, bedrock lithology, surficial deposits, and structural features information.
- Hazard assessment including Geologic hazards (seismic, slope related, etc.) and Hydrologic hazards (flooding, erosion, etc.)
- Conclusions and recommendations
- Maps
Hazard Maps
are made for specific hazards like earthquake, slope
movement, liquefaction, etc.
