5 – 1
CHAPTER
5
Fundamentals of Soils
1. A contractor is excavating fill material from a borrow site to be used to construct a compacted
fill foundation for a parking garage. She has determined that 5,000 compacted cubic yards of soil
are required to complete the structural fill. The in situ density of the fill material is 110 pounds
per cubic foot, the loose density is 88 pounds per cubic foot, and the compacted density is 125
pounds per cubic foot.
a. What is the percent swell for the fill material?
b. What is the percent shrinkage for the fill material?
c. How many loose cubic yards must be hauled in trucks from the borrow site to construct the
fill?
d. How many bank cubic yards must be excavated and loaded on the trucks to construct the fill?
5 – 2
2. A contractor is planning to haul in fill material to backfill around the foundation of a large
commercial building. Tests on the fill material indicate a bank wet unit weight of 98 pounds per
cubic foot, a bank dry unit weight of 95 pounds per cubic foot, and a swell of 18%. When
compacted to the desired density, the wet soil weighs 111 pounds per cubic foot. Proctor tests
indicate that the optimum moisture content for compacting the soil is about 8%. The total volume
of the required backfill is 10,000 compacted cubic yards.
a. How many bank cubic yards of soil must be excavated and hauled to the project site to
construct the backfill?
b. How many gallons of water should be added to each loose cubic yard of soil delivered to the
project site to increase the soil moisture content to 8%?
5 – 3
3. A contractor is planning to use a hydraulic excavator to remove the soil for the construction of
the foundation for a new hotel. He has determined from the project plans that 3,000 bank cubic
yards must be excavated and that 817 compacted cubic yards will be required to backfill the
completed foundation. The contractor plans to stockpile the soil needed for backfill on site and
haul the excess soil off site using dump trucks that have a heaped capacity of 30 loose cubic yards.
The contractor had the soil tested and determined that the bank density is 2,800 pounds per cubic
yard, the loose density is 2,295 pounds per cubic yard, and the compacted density is 3,256 pounds
per cubic yard.
a. What is the percent swell for the soil?
𝑐𝑢.𝑓𝑡.−2,295 𝑙𝑏𝑠
𝑐𝑢.𝑓𝑡.)(100%)
𝑐𝑢.𝑓𝑡.=22%
b. What is the percent shrinkage for the soil after being compacted?
c. How many bank cubic yards should be stockpiled to be used for the backfill operation?
d. How many truckloads of excess material should be hauled off site, if the trucks are fully loaded
to their heaped capacity?
5 – 4
4. A contractor is constructing streets for a residential project. She has decided to use scrapers to
excavate, haul, and spread fill material to construct the subgrade for the streets. Soil tests on the
fill material indicate a wet unit weight of 115 pounds per bank cubic foot and a dry unit weight of
110 pounds per bank cubic foot. Compaction tests indicate that the optimum moisture content for
the fill material is 8%. The scrapers can deliver the fill material to the project site at the rate of
150 loose cubic yards per hour. Swell for the fill material is estimated to be 20%, and shrinkage
is estimated to be 12% when compacted to the design density. How many gallons of water must
the contractor deliver to the project site per hour, if she wants to increase the moisture content to
8% and keep up with the productivity of the scrapers? (Note: Water weighs 8.33 pounds per
gallon.)
5 – 5
5. A contractor is excavating fill material weighing 2,996 pounds per bank cubic yard with a
loader and hauling the material in dump trucks to a fill area 4 miles away. Soil tests indicate that
the dry unit weight of a bank cubic yard of fill material is 2,800 pounds.
a. What is the in situ moisture content of the soil the contractor is excavating?
𝑐𝑢.𝑦𝑑. =7%
b. Compaction tests indicate that the optimum moisture content of the soil is 10%. How many
gallons of water per bank cubic yard of soil should be added to raise the moisture content to
10%? (Note: Water weighs 8.33 pounds per gallon.)
8.33 𝑙𝑏𝑠
𝑔𝑎𝑙𝑙𝑜𝑛 =10.8𝑔𝑎𝑙𝑙𝑜𝑛
c. How many gallons of water should be added to each loose cubic yard of soil as it is being
spread on the fill site to bring the moisture content up to the desired 10%? Soil tests indicate
that the soil swell is about 28%.
8.33 𝑙𝑏𝑠
𝑔𝑎𝑙𝑙𝑜𝑛 = 8.4𝑔𝑎𝑙𝑙𝑜𝑛
d. How many truck tractors with 5,000-gallon water trailers should be used to apply the water, if
they can apply water at a rate of 8 gallons per minute and the dump trucks can spread the fill
material at a rate of 300 loose cubic yards per hour?
5 – 6
6. A contractor has a contract for the construction of a shopping center and a large parking lot.
Soil tests indicate the natural soil has a high clay content, requiring either stabilization or
replacement to make an acceptable subgrade for the parking lot pavement. The in situ soil weighs
2,900 pounds per bank cubic yard at a moisture content of 5%. Tests indicate that adding 3% lime
by dry unit weight of the soil would stabilize the soil adequately. How much lime (in pounds)
should the contractor purchase if an 8-inch layer of soil is to be stabilized, and the parking lot
measures 150 feet by 390 feet?
The first step is to determine the dry unit weight of the soil. The dry unit weight is
⁄)
(100%+ 5%)= 2,762 𝑙𝑏.𝐵𝐶𝑌
Now we can determine the amount of lime required to be
The volume of the soil to be treated is
5 – 7
7. A contractor has a contract for the construction of a new runway for a regional airport. The
contract specifications require cement stabilization of the natural soil to a depth of 8 inches before
an aggregate base course is placed. Soil tests on the existing soil indicate a wet unit weight of 107
pounds per bank cubic foot and a dry unit weight of 103 pounds per bank cubic foot. The contract
specifies that the cement content required for the stabilized subgrade is 4% of the soil dry unit
weight.
a. What is the moisture content of the existing soil?
𝑐𝑢.𝑦𝑑. = 3.9%
b. How much cement (in pounds) should the contractor add to each bank cubic yard of existing
soil to achieve the cement content specified in the contract?
The amount of cement required to be
5 – 8
8. A contractor has a contract for the construction of a new post office. Part of the project involves
the construction of a large paved truck storage area. The contract requires that the storage area
receive an asphalt concrete surface placed on an asphalt-stabilized base course. The granular base
course material being trucked in to the construction site weighs 2,800 pounds per bank cubic yard
at a moisture content of 2%. The contract specifies that the asphalt content in the compacted base
course be 2% of the dry weight of the soil. Soil tests taken on the base course material indicate a
swell of 12% and a shrinkage of 8% when compacted to the design density. The contractor
estimates that 2,000 loose cubic yards of base course material are required for the storage area.
How many gallons of asphalt should the contractor order for the base course, if one gallon of
asphalt weighs 8 pounds?
The amount of asphalt required to be