Transcript For mid-term question #6

Rock and steel samples <shown in class>
The iron nail is badly rusted, while the zinc-coated nail
looks brand new.
The granite cobble stone is worn and rounded, but still
has a lot of strength. In contrast, the old man-made
concrete aggregate crumbles easily because soil
conditions dissolved it.
The moral of the story is that HOW we build things
counts a lot. Soil conditions can greatly affect how
durable and safe buildings are.
For mid-term question #6:
Think of modern cars – like a Hummer or Toyota
Tundra. A Ford F-250 weighs about 8,000 pounds
and full of technology.
Faster and safer, but very expensive when damaged
(easy to ‘total’ it).
We don’t die as often (highway deaths are down
even with increasing population, but we sure lose a
lot of money because our stuff is so expensive
This week’s weather
<fits Chapter 9>
104 degrees F – what if today were humid also?
n humid regions, 90 degrees F can be a deadly
heat wave.
Heat stress index adds a humidity factor to heat
In winter, we add a ‘wind’ chill factor to the cold.
See page 312 in
the textbook
Page 70 – Heat Waves
Europe 2003 – 35,000 deaths due to heat, 14,500 in France
Temperature Inversions
Temperature Inversions
Peter Sinks presents ideal
conditions for deep winter
weather inversions – cold air has
no where to go, so it
concentrates.
Utah has some of the
nation’s coldest winter
temperatures – we are far
from the ocean, far from
sea level and far from the
equator.
Heating & Cooling Degree Days - USA
White and pink
areas have no
summer cooling load
(> 65 degrees F)
Red areas > 9,000
cooling degree days
What’s wrong with lots of water in the
air on a hot day?
- The water is hot also
- Body perspiration by evaporative cooling can’t
occur if the air is already full of evaporated
water
- Why is there no wind ‘chill’ factor with
hot/humid air? <ordinarily wind brings you air
that is cooler than your own body, but . . . .>
Wind Chill and Heat Stress Index
pages 89 and 108
Wind chill - Skin has a boundary
layer of warm, humid air that is
removed by wind, resulting in
‘wicking’ heat away from the body,
making cold more penetrative.
Today’s earthquake in China – 6.9M
- 75 dead
- Unreinforced buildings with mud roofs
- Heavy rain preceded quake
- Water adds weight and helps loosen and
dissolve earthen material.
This is the blocked drain
at the Constitution Park
retention/detention
basin.
They used sandbags AND
a . . . . levee.
I wonder why one drain is double-blocked, but
with a gap – what is the value of sandbags
with a gap?
If a duck is settling in, is the basin for
retention or detention?
At Allred’s house
“flash flood”
conditions will be
avoided by putting
careful drains
underneath hard
surfacing so that rain
water has some place
to go – sink into the
ground.
Good drains will also
help prevent
damaging and
slippery ice on the
surface .
Excavate, remove “fines” (fine
material) and replace
By removing clay and silt, the
remaining cobblestones add
strength underground and
provide pore spaces for
collecting rain water until it
can finish draining into the
soil.
Even in dry Utah, flash
rainstorms can cause severe
surface flooding. Drains can
easily get blocked by debris.
Is it true that
it’s not so
much where
you build as
HOW you
build?
Miller campus
steel-frame
building, with
lightweight walls
and ceiling –
easily shaken by
a passing train,
but is probably
won’t fall down
in a quake.
Reverse the concept that modern
life is turning hazards into disasters
and disasters into catastrophes:
instead, by making hard choices to
fund better infrastructure and
building practices, we turn
catastrophes back into merely
‘cracks in the sidewalk.’
Some Intervention Terminology:
Drain tiles, surface & underground
Grading: terraces, lower angles
Reduce ‘loading’ by buildings and vegetation
Earth anchors and other retaining structures
such as gabions, pilings, seed mats, engineering
fill, bolts, spread footings.
Do these play a role in Chapter 8 “Soils and
Subsidence”?
Creep
Slump
Flow
Fall
<once again a function of slope and water>
But what about soil structure?
<rock, sand, silt, clay>
Lava beds in
southern Idaho
Geothermal
heat on
west side of
Utah
Volcanoes and
cinder cones
Lava beds in
southern Utah
old sediments
(sandstone) with
fossil fuels – oil, coal,
gas, shale, tar sand
But it is also true that we are
running out of good building sites
on the best ground:
<page 227>
Not too wet and not too steep?
<yes>
Has this slope changed its “angle of
repose”?
Depends on what is done
with the steepened portions
Gabions, retaining walls, earth anchors,
drain pipe, surface water removal,
‘engineered fill’ material
Some students conclude to be
cynical –
‘We’re damned if we do and
damned if we don’t.’
Is that really true?
Many land formations have been
“vertically deforming” for millions of years,
but that does not mean we must:
- add load to vulnerable soils
(such as by heavy buildings);
- pump out water;
- pump in water;
- remove minerals;
- use weak foundations;
- build in ‘chutes’ or flow paths;
Chapter 8
Mr. Allred’s “Sets of Threes”
in Soils
Core, mantle and crust.
Crust as bedrock, regolith, soil
Soil as mineral, air/water, organic
Mineral as sand, silt, clay
Regolith:
blanket rock, fractured, crumbling
transition between bedrock and soil
Regolith is being weathered – physical
and chemical breakdown
Soils Pyramid
page 246
This set of “three”
is mostly about
how well soils
drain, how
permeable they
are, how well
water
percolates
through.
In the case of clay,
how stable the soil
is when wet.
Source unknown: probably googleimages.com and USDA, undated.
Highland campus ash can
Why?
<freeze/thaw, salt, gravity weight>
Page 243
Soil Profile
or
“Horizons”
Point out
bedrock,
regolith, soil
Source: EnchantedLearning.com and
Googleimages.com
The presence of distinct soil
horizons suggests stability of the
ground – it takes hundreds, even
thousands of years to develop soil
horizons (except in some extremely
wet/hot climates)
What can you conclude if excavation
shows unconsolidated, unsorted
materials of different types?
1. Un-layered, un-sorted soils are likely
produced by recent cataclysm, like quakes,
landslides, etc.
2. Strongly layered soils indicate long-term
stable conditions at that location, probably
less prone to soil failure.
Allred
excavation:
1. Humus layer
2. Root layer
3. Salt layer
4. Cobbles
Hardpan or compacted soils have been
‘cemented’ by chemical action to be
nearly impermeable.
In contrast, permeable soils allow
water to percolate through, helping
prevent surface flooding or soil
saturation that can cause building
damage by subsidence or collapse.
Alluvial fans or river deltas
page 248
Implications?
What about a ‘fan off-set’?
<shown on the board>
What is wrong with building on:
- alluvial fan?
- river delta?
Alluvial fan with an off-set?