Soil Texture Triangle - Soil Classification, Soil Mechanics Video Lecture - Civil Engineering (CE)

so in this video we're going to learn
how to use a soil texture diagram or
it's called a soil triangle to determine
the amount of sand silt and clay in a
soil sample so at the bottom of this
sheet we have a table the table has the
percent of each sand silt and clay the
texture name and then the properties of
that clay which are dependent on the
different types of minerals that it has
so for the first example we have 75
percent sand 10 percent silt and 15
percent clay now remember if you add
sand silt and clay makes loam so it
makes sense that that would be sandy
loam but you can figure this out by
going here's the percents and so there's
seventy-five percent of that so here's a
hundred percent here seventy here's
eighty and there are two lines there's
one that goes on the left and there's
one that goes on the right so you're
going to figure out seventy-five you're
going to go in between seventy and
eighty and you're going to go towards
the left
so in between seventy and eighty is
about right here and you will just put a
little you can use a highlighter if
you'd like you're going to get in
between the lines that are 70 and 80 70
and 80 then you're going to go figure
out where it's ten percent silt so
you'll find the silt line move the paper
so now you see that's ten percent silt
so anything where along this line is 10
percent 20 percent 30 percent so you're
always going to look at the line on the
left okay so we're looking for 10
percent silt so we'll take our
highlighter and we're going to highlight
10 percent silt and where these two
lines intersect that is should be where
your clay
so if we go to clay you want to turn it
to the clay side all of this is 10% 20%
etc so it looks like between 10 and 20
is 15 percent it's 15 percent clay and
indeed that was 15 percent clay so
that's where we got sandy loam here so
let's do the second one together got ten
percent sand
eighty-three percent silt and seven
percent clay so we're going to go to the
sand we're going to go fine ten percent
sand so it's going to be somewhere and I
might use a different color you can
start off with a few different color
highlighters remember I told you to go
the line on the left not the right now
we're going to go to eighty-three
percent silt so you can turn up to the
silt side and you will find the 83 here
70 here's 80 hears 90 and you're going
to go to the left so 83 is probably
closer a little bit closer to 80 okay
and so far we could figure out just
based on those two that it's silt but
let's double check seven percent clay so
we're going to go to the clay parts face
it towards you
to where this line is towards you
and we're going to go to here's 10
here's five so we're going to go to
seven so seven would be about probably
between ten and five so we're gonna just
kind of make a line here and indeed then
we're going to write SIL here okay so if
you use the if you look at this um table
here silt has medium nutrient holding
capacity it filters water pretty good
it can hold water pretty well aeration
is the amount of pore space so it has a
pretty decent pore space and it's
moderately easy to work with so I would
put properties under properties pretty
good all around so now let's look at
this third example see 42% sand we're
not sure how much silt 37% clay so to
figure out that the amount of silt the
whole thing has to add up to 100 so
we'll add these two together 42 plus 37
is 79 100% minus 79 so that's 21 percent
silt so let's start with the sand 42%
sand and I might use a blue one this
time so here's sand 42% sand so 40 50
and remember I'm always looking at the
line on the left so 42 is going to be
fairly close somewhere along that line
21 percent silt so I'm going to get over
to this silt I go to 20 always look at
the line on the Left there's 20 there's
30 so 21 is probably going to be close
really close to 20 and I can mark this
right here and it would be classified as
a clay loam but before I totally feel
comfortable with that
I'm going to double check to make sure
my clay matches up to 37 percent mmm
situated so clay is directly in front of
me and then I'm going to find here's 30
here's 40 and I'm looking at the lines
on the left
so 35 is probably in the middle so 37
would be about right here and so we're
all three of those intersect would be a
clay loam and clay is pretty good
because it's negative and nutrients a
lot of the nutrients are positive it's
good nutrient retention and because it
is a limb it's has good porosity and
permeability is equally as good so it's
probably very workable as well
so 4d if you want to continue listening
to this then you can walk you through
one or two more otherwise you can go to
the end of the video and I will show you
the answer key so 4d we're going to have
to figure out again 52 and 27 is a
hundred is 79 and 100 minus 79 would be
21% sand so 21% sand will start the
chart 21 and I'm just going to do it in
this pen here so 21% sand would be
somewhere around in here remember you're
going to go not the right line but the
one that goes to the left so 21% sand
how much silt 52 percent silt so I'm
going to get over to the silt have that
right in front of me here's 50 or 60 so
52 is going to be again on the left it's
going to be between this line and this
line so 52 it's going to be somewhere in
52 might be somewhere come on that line
let's do let's figure out how much clay
there is 27% clay
so I'm going to go back to the clay here
have that right in front of me I'm
looking for 27%
so here's 20 here's 30 here's 25 so 27
would be somewhere in them little hair
and I'm going to go all the way up so
it's going to be closer to that side and
that is a silt loam and silt loam is
probably pretty good all around really
what's not good in terms of workability
is clay not good in terms of
permeability as clay because of course
pore space would be so small and sand
would have high permeability because of
the large grains and large pore spaces
between the grains okay I'll do one more
e so with E you've got 35 and 50 is 85
so you've got fifteen percent sand so
you're going to go sand here's twenty
here's 10 so you're going to get a 15
it's going to be somewhere in the middle
here so I'm just going to draw a line
kind of somewhat goes through the middle
there then I have 35% so we go over to
silt 20 35 and this would be it right
here
so we would call that a clay and if you
want to double check to make sure that
it's 50 percent clay then here's the
clay
here's
clay here's the 50 so it would be about
right right there alright so you should
have in the end this would be your
results thank you