Ihab Saad – Soil Properties

Music. Hello again, and welcome to

construction measurement 329,

construction equipment.

So today we're going to start talking a little bit

about earth moving equipment and soil properties. So we need to

know about some of the properties of soil before we start discussing

any details on the equipment itself.

So things you should have learned in soils class, have you been

paying attention? Any mass of soil consists of solid particles with

voids in between,

whether it's rock, whether it's sand, clay, any type of soil. It's

soil particles with voids in between, and these voids can be

filled either with water or air. If it's submerged or under the

water table, then the voids are going to be filled with water

then. Or if it's above the water table and not submerged, then it's

going to be filled with air,

just having a look at this graph shows basically what we're talking

about.

It has solid

solids, and then again, if partially submerged, it's going to

have water and it might have air. All of this may be filled with

water if it's totally submerged, and all of this is going to be

filled with air if it's not submerged at all. And these can be

measured either by volume or by mass. So looking at the volume we

have VT, which is the total volume of that sample of soil, with vs

being the volume of solids. And VV is the volume of voids, which can

be divided into VW, volume of water and VA, volume of air. On

the other hand, if we measure it by mass, then MT is the total

mass. Notice here that MT is not up to the top, because air doesn't

have any mass. Ma is equal to zero, so MT is going to be just

equal to MS, the mass of soil, the solids and MW, the mass of water.

If you want to calculate the weight of that soil, the unit

weight is going to be the total weight of the soil divided by the

total soil volume. So w over V, we get a soil sample we weight, and

then we divide that weight by the volume, and that gives the unit

weight, or the density of that soil dry unit weight, however, yd

is going to be basically the weight of the soil solids,

excluding the water. So we put it in the oven to try it and get rid

of all the included water. And then we weigh the solids divided

by the same volume, which is going to be total soil volume. And that

gives us the dry unit weight,

the moisture content, which is the amount of moisture in that soil,

is going to be

calculated as the wet unit weight minus the dry unit weight, again,

by drying the soil in an oven getting rid of the water. So wet

unit weight minus dry unit weight, which is basically the weight of

water times 100%

divided by the dry unit weight. It can range from 0% if the soil is

totally dry in a desert or something like that, to several

100% because in some cases, the weight of the water and the volume

of the water can exceed the volume of solids themselves. So in this

case, it can be more than 100%

water content for most soils is well under 0%

although it can range up to 500% or higher in submarine and organic

soils, soils that can hold a lot of water, or soils that are

totally submerged as marine soils.

Now looking at an example for these calculations. Excavated

material has a wet weight, wet unit weight of 94.3

pounds per cubic foot, that's PCF, and a dry unit weight of 87 point

3.3,

PCF, and the embankment will be compacted to a dry weight of 114

pcf. Compacting the soil means getting rid of the voids totally,

or to a certain level. So getting rid of the air,

making the soil particles come closer to each other, and the

desired water content is 12%

the next section of the embankment is 115,000, cubic yards. What type

of cubic yards we're going to discuss that in a minute? What is

the moisture content of the excavated soil? How many cubic

yards of excavation will be required to construct the

embankment, and do we need to add.

Five. So this is going to be times 100 plus 20 525.

Divided by 100% minus percent shrinkage. So this way we can

convert. If I know the compacted volume, I can get and knowing the

swell and the shrinkage percentages, I can get the loose

volume, and I can get the bank volume also. So we can convert

between these three different types, knowing these two equations

to

look at an example here, a soil weighs 19 160

pounds per loose cubic yard. Now notice that this is loose cubic

yard, which means when we excavate it, when we disturbed it after the

excavation, that was the weight, as it was measured, and it's not

in its natural condition, is 2800 pounds per band cubic yard and

compacted. Now again, the density is going to increase. So the

weight per unit volume is going to increase. 3500 pounds per

compacted cubic yards. How many bank cubic yards and compacted

cubic yards are contained in 1 million loose cubic yards? Again,

based on the equations that we just learned

to get the bank volume, we multiply the loose cubic yards,

the loose volume times the loose density divided by the bank

density, and that gives us 700,000 bank cubic yards. To get the

compacted volume. We notice that it's going to be even much less

than that, which is going to be 560,000

compacted cubic yards, that shows you the amount of compaction that

this soil is going to go through. So that tells you how much more

soil do we need to bring from out of that site, just to compact,

to fill the holes that resulted from the excavation.

Another example here in building a parking lot for a new school,

10,000 compacted cubic yards are required for the fill.

The contractor has selected the source for the fill and found out

that the bank density is going to be 2800

pounds per cubic yard.

What kind of cubic yards in this case? Well, the question is told

is is given here. The answer is given, bank density. So this is

going to be bank cubic yards. The loose density is 2240

pounds per cubic yard, also loose cubic yards. And the compacted

density is 3415

pounds per cubic yard, in this case, CcY

compacted cubic yards. He plans to excavate the fill material with a

wheeled loader and load dump trucks that will haul the soil to

the construction site.

What is the percent swell for the fill material? What's the percent

shrinkage for the feed material, how many loose cubic yards must

be? Must the contractor haul in the dump trucks? How many bank

cubic yards must the contractor excavate with the loaded so again,

from this information, we can answer all of these different

questions.

First step is to calculate the swell and the shrinkage from these

different numbers using the equations that we already learned

about. So the percent swell is 25%

the percent shrinkage is 18% based on these two different

calculations.

So how many loose cubic yards must the contractor haul in the dump

trucks? The volume loose is going to be the volume compacted again

using the same equations that we learned about before, times 100%

plus percent swell divided by 100%

minus percent shrinkage, so is going to be 10,000 that's the

compacted volume that we know about, times 125%

divided by 82%

and that gives 1500 15,224

new loose cubic yards. So when you measure the soil on the trucks,

which is going to be loose, this is the volume that you need to

bring to the site.

How many bank cubic yards must the contractor excavate with the

loader again to achieve these loose cubic yards? So it's gonna,

it's gonna be that that volume 12,000 195

bank cubic yards are going to produce 10,000 compacted cubic

yards.

And that's the end of this. This lecture about soil properties.