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Compaction

Environmental Engineering · FE Reference Handbook section

Environmental Engineering
3 formulas
10 exam-style examples
~51 min
All Environmental Engineering lectures

Core formulas for this FE topic

Definitions, applicability, units, assumptions and worked examples for each relation.

Worked exam-style examples

The four ways this section is written on the real exam — thoughts first, then equations, then substitution.

Example 1
Compaction — solve for compaction ratio — Compaction

compaction ratio of solid waste in a landfill cell Given compacted unit weight (gamma_c) = 495.0 kg/m^3; loose unit weight (gamma_l) = 200.0 kg/m^3, determine the compaction ratio (CR).

Given

  • compactedunitweight(gammac)=495.0kg/m3compacted unit weight (gamma_c) = 495.0 kg/m^3
  • looseunitweight(gammal)=200.0kg/m3loose unit weight (gamma_l) = 200.0 kg/m^3

Find

compaction ratio (CR)

Start with the thinking

  • The governing relation printed in this handbook section is Compaction.
  • Everything except CR is given, so isolate CR symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Compaction of solid waste is characterized by the compaction ratio comparing compacted density to loose density in a landfill.

Step-by-step solution

  1. Step 1 — State the governing relation:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  2. Step 2 — Rearrange symbolically for CR:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  3. Step 3 — List the givens: compacted unit weight (gamma_c) = 495.0 kg/m^3, loose unit weight (gamma_l) = 200.0 kg/m^3.

  4. Step 4 — Substitute the given values:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  5. Step 5 — Evaluate:

    CR=2.4750CR = 2.4750
  6. Step 6 — Check: returning CR = 2.4750 to

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
CR=2.4750CR = 2.4750

Why the other options are there

  • 4.9500 — kept a factor of two that cancels in the correct rearrangement.
  • 1.2375 — dropped that same factor in the other direction.
  • 2.7225 — rounded an intermediate value before the final step.

Reference: FE Handbook — Compaction

Example 2
Compaction — solve for compacted unit weight — Compaction (2)

compaction of municipal solid waste by a landfill compactor Given loose unit weight (gamma_l) = 295.0 kg/m^3; compaction ratio (CR) = 4.6000, determine the compacted unit weight (gamma_c) in kg/m^3.

Given

  • looseunitweight(gammal)=295.0kg/m3loose unit weight (gamma_l) = 295.0 kg/m^3
  • compactionratio(CR)=4.6000compaction ratio (CR) = 4.6000

Find

compacted unit weight (gamma_c), in kg/m^3

Start with the thinking

  • The governing relation printed in this handbook section is Compaction.
  • Everything except gamma_c is given, so isolate gamma_c symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Compaction of solid waste is characterized by the compaction ratio comparing compacted density to loose density in a landfill.

Step-by-step solution

  1. Step 1 — State the governing relation:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  2. Step 2 — Rearrange symbolically for gamma_c:

    γc=CR γloose\gamma_{c} = CR\,\gamma_{loose}
  3. Step 3 — List the givens: loose unit weight (gamma_l) = 295.0 kg/m^3, compaction ratio (CR) = 4.6000.

  4. Step 4 — Substitute the given values:

    γc=4.6000 γloose\gamma_{c} = 4.6000\,\gamma_{loose}
  5. Step 5 — Evaluate:

    \gamma_{c} = 1357\ \text{kg/m^3}
  6. Step 6 — Check: returning gamma_c = 1,357 kg/m^3 to

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
\gamma_{c} = 1357\ \text{kg/m^3}

Why the other options are there

  • 2,714 — kept a factor of two that cancels in the correct rearrangement.
  • 678.5 — dropped that same factor in the other direction.
  • 1,493 — rounded an intermediate value before the final step.

Reference: FE Handbook — Compaction

Example 3
Compaction — solve for loose unit weight — Compaction (3)

waste compaction ratio used to estimate landfill airspace consumption Given compacted unit weight (gamma_c) = 910.0 kg/m^3; compaction ratio (CR) = 4.7500, determine the loose unit weight (gamma_l) in kg/m^3.

Given

  • compactedunitweight(gammac)=910.0kg/m3compacted unit weight (gamma_c) = 910.0 kg/m^3
  • compactionratio(CR)=4.7500compaction ratio (CR) = 4.7500

Find

loose unit weight (gamma_l), in kg/m^3

Start with the thinking

  • The governing relation printed in this handbook section is Compaction.
  • Everything except gamma_l is given, so isolate gamma_l symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Compaction of solid waste is characterized by the compaction ratio comparing compacted density to loose density in a landfill.

Step-by-step solution

  1. Step 1 — State the governing relation:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  2. Step 2 — Rearrange symbolically for gamma_l:

    γl=γcompactedCR\gamma_{l} = \dfrac{\gamma_{compacted}}{CR}
  3. Step 3 — List the givens: compacted unit weight (gamma_c) = 910.0 kg/m^3, compaction ratio (CR) = 4.7500.

  4. Step 4 — Substitute the given values:

    γl=γcompacted4.7500\gamma_{l} = \dfrac{\gamma_{compacted}}{4.7500}
  5. Step 5 — Evaluate:

    \gamma_{l} = 191.6\ \text{kg/m^3}
  6. Step 6 — Check: returning gamma_l = 191.6 kg/m^3 to

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
\gamma_{l} = 191.6\ \text{kg/m^3}

Why the other options are there

  • 383.2 — kept a factor of two that cancels in the correct rearrangement.
  • 95.7895 — dropped that same factor in the other direction.
  • 210.7 — rounded an intermediate value before the final step.

Reference: FE Handbook — Compaction

Example 4
Compaction — solve for compaction ratio (case 2) — Compaction (4)

compaction ratio of solid waste in a landfill cell Given compacted unit weight (gamma_c) = 930.0 kg/m^3; loose unit weight (gamma_l) = 250.0 kg/m^3, determine the compaction ratio (CR).

Given

  • compactedunitweight(gammac)=930.0kg/m3compacted unit weight (gamma_c) = 930.0 kg/m^3
  • looseunitweight(gammal)=250.0kg/m3loose unit weight (gamma_l) = 250.0 kg/m^3

Find

compaction ratio (CR)

Start with the thinking

  • The governing relation printed in this handbook section is Compaction.
  • Everything except CR is given, so isolate CR symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Compaction of solid waste is characterized by the compaction ratio comparing compacted density to loose density in a landfill.

Step-by-step solution

  1. Step 1 — State the governing relation:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  2. Step 2 — Rearrange symbolically for CR:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  3. Step 3 — List the givens: compacted unit weight (gamma_c) = 930.0 kg/m^3, loose unit weight (gamma_l) = 250.0 kg/m^3.

  4. Step 4 — Substitute the given values:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  5. Step 5 — Evaluate:

    CR=3.7200CR = 3.7200
  6. Step 6 — Check: returning CR = 3.7200 to

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
CR=3.7200CR = 3.7200

Why the other options are there

  • 7.4400 — kept a factor of two that cancels in the correct rearrangement.
  • 1.8600 — dropped that same factor in the other direction.
  • 4.0920 — rounded an intermediate value before the final step.

Reference: FE Handbook — Compaction

Example 5
Compaction — solve for compacted unit weight (case 2) — Compaction (5)

compaction of municipal solid waste by a landfill compactor Given loose unit weight (gamma_l) = 200.0 kg/m^3; compaction ratio (CR) = 4.2500, determine the compacted unit weight (gamma_c) in kg/m^3.

Given

  • looseunitweight(gammal)=200.0kg/m3loose unit weight (gamma_l) = 200.0 kg/m^3
  • compactionratio(CR)=4.2500compaction ratio (CR) = 4.2500

Find

compacted unit weight (gamma_c), in kg/m^3

Start with the thinking

  • The governing relation printed in this handbook section is Compaction.
  • Everything except gamma_c is given, so isolate gamma_c symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Compaction of solid waste is characterized by the compaction ratio comparing compacted density to loose density in a landfill.

Step-by-step solution

  1. Step 1 — State the governing relation:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  2. Step 2 — Rearrange symbolically for gamma_c:

    γc=CR γloose\gamma_{c} = CR\,\gamma_{loose}
  3. Step 3 — List the givens: loose unit weight (gamma_l) = 200.0 kg/m^3, compaction ratio (CR) = 4.2500.

  4. Step 4 — Substitute the given values:

    γc=4.2500 γloose\gamma_{c} = 4.2500\,\gamma_{loose}
  5. Step 5 — Evaluate:

    \gamma_{c} = 850.0\ \text{kg/m^3}
  6. Step 6 — Check: returning gamma_c = 850.0 kg/m^3 to

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
\gamma_{c} = 850.0\ \text{kg/m^3}

Why the other options are there

  • 1,700 — kept a factor of two that cancels in the correct rearrangement.
  • 425.0 — dropped that same factor in the other direction.
  • 935.0 — rounded an intermediate value before the final step.

Reference: FE Handbook — Compaction

Example 6
Compaction — solve for loose unit weight (case 2) — Compaction (6)

waste compaction ratio used to estimate landfill airspace consumption Given compacted unit weight (gamma_c) = 515.0 kg/m^3; compaction ratio (CR) = 2.6500, determine the loose unit weight (gamma_l) in kg/m^3.

Given

  • compactedunitweight(gammac)=515.0kg/m3compacted unit weight (gamma_c) = 515.0 kg/m^3
  • compactionratio(CR)=2.6500compaction ratio (CR) = 2.6500

Find

loose unit weight (gamma_l), in kg/m^3

Start with the thinking

  • The governing relation printed in this handbook section is Compaction.
  • Everything except gamma_l is given, so isolate gamma_l symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Compaction of solid waste is characterized by the compaction ratio comparing compacted density to loose density in a landfill.

Step-by-step solution

  1. Step 1 — State the governing relation:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  2. Step 2 — Rearrange symbolically for gamma_l:

    γl=γcompactedCR\gamma_{l} = \dfrac{\gamma_{compacted}}{CR}
  3. Step 3 — List the givens: compacted unit weight (gamma_c) = 515.0 kg/m^3, compaction ratio (CR) = 2.6500.

  4. Step 4 — Substitute the given values:

    γl=γcompacted2.6500\gamma_{l} = \dfrac{\gamma_{compacted}}{2.6500}
  5. Step 5 — Evaluate:

    \gamma_{l} = 194.3\ \text{kg/m^3}
  6. Step 6 — Check: returning gamma_l = 194.3 kg/m^3 to

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
\gamma_{l} = 194.3\ \text{kg/m^3}

Why the other options are there

  • 388.7 — kept a factor of two that cancels in the correct rearrangement.
  • 97.1698 — dropped that same factor in the other direction.
  • 213.8 — rounded an intermediate value before the final step.

Reference: FE Handbook — Compaction

Example 7
Compaction — solve for compaction ratio (case 3) — Compaction (7)

compaction ratio of solid waste in a landfill cell Given compacted unit weight (gamma_c) = 870.0 kg/m^3; loose unit weight (gamma_l) = 135.0 kg/m^3, determine the compaction ratio (CR).

Given

  • compactedunitweight(gammac)=870.0kg/m3compacted unit weight (gamma_c) = 870.0 kg/m^3
  • looseunitweight(gammal)=135.0kg/m3loose unit weight (gamma_l) = 135.0 kg/m^3

Find

compaction ratio (CR)

Start with the thinking

  • The governing relation printed in this handbook section is Compaction.
  • Everything except CR is given, so isolate CR symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Compaction of solid waste is characterized by the compaction ratio comparing compacted density to loose density in a landfill.

Step-by-step solution

  1. Step 1 — State the governing relation:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  2. Step 2 — Rearrange symbolically for CR:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  3. Step 3 — List the givens: compacted unit weight (gamma_c) = 870.0 kg/m^3, loose unit weight (gamma_l) = 135.0 kg/m^3.

  4. Step 4 — Substitute the given values:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  5. Step 5 — Evaluate:

    CR=6.4444CR = 6.4444
  6. Step 6 — Check: returning CR = 6.4444 to

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
CR=6.4444CR = 6.4444

Why the other options are there

  • 12.8889 — kept a factor of two that cancels in the correct rearrangement.
  • 3.2222 — dropped that same factor in the other direction.
  • 7.0889 — rounded an intermediate value before the final step.

Reference: FE Handbook — Compaction

Example 8
Compaction — solve for compacted unit weight (case 3) — Compaction (8)

compaction of municipal solid waste by a landfill compactor Given loose unit weight (gamma_l) = 355.0 kg/m^3; compaction ratio (CR) = 4.9000, determine the compacted unit weight (gamma_c) in kg/m^3.

Given

  • looseunitweight(gammal)=355.0kg/m3loose unit weight (gamma_l) = 355.0 kg/m^3
  • compactionratio(CR)=4.9000compaction ratio (CR) = 4.9000

Find

compacted unit weight (gamma_c), in kg/m^3

Start with the thinking

  • The governing relation printed in this handbook section is Compaction.
  • Everything except gamma_c is given, so isolate gamma_c symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Compaction of solid waste is characterized by the compaction ratio comparing compacted density to loose density in a landfill.

Step-by-step solution

  1. Step 1 — State the governing relation:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  2. Step 2 — Rearrange symbolically for gamma_c:

    γc=CR γloose\gamma_{c} = CR\,\gamma_{loose}
  3. Step 3 — List the givens: loose unit weight (gamma_l) = 355.0 kg/m^3, compaction ratio (CR) = 4.9000.

  4. Step 4 — Substitute the given values:

    γc=4.9000 γloose\gamma_{c} = 4.9000\,\gamma_{loose}
  5. Step 5 — Evaluate:

    \gamma_{c} = 1740\ \text{kg/m^3}
  6. Step 6 — Check: returning gamma_c = 1,740 kg/m^3 to

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
\gamma_{c} = 1740\ \text{kg/m^3}

Why the other options are there

  • 3,479 — kept a factor of two that cancels in the correct rearrangement.
  • 869.8 — dropped that same factor in the other direction.
  • 1,913 — rounded an intermediate value before the final step.

Reference: FE Handbook — Compaction

Example 9
Compaction — solve for loose unit weight (case 3) — Compaction (9)

waste compaction ratio used to estimate landfill airspace consumption Given compacted unit weight (gamma_c) = 755.0 kg/m^3; compaction ratio (CR) = 4.8500, determine the loose unit weight (gamma_l) in kg/m^3.

Given

  • compactedunitweight(gammac)=755.0kg/m3compacted unit weight (gamma_c) = 755.0 kg/m^3
  • compactionratio(CR)=4.8500compaction ratio (CR) = 4.8500

Find

loose unit weight (gamma_l), in kg/m^3

Start with the thinking

  • The governing relation printed in this handbook section is Compaction.
  • Everything except gamma_l is given, so isolate gamma_l symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Compaction of solid waste is characterized by the compaction ratio comparing compacted density to loose density in a landfill.

Step-by-step solution

  1. Step 1 — State the governing relation:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  2. Step 2 — Rearrange symbolically for gamma_l:

    γl=γcompactedCR\gamma_{l} = \dfrac{\gamma_{compacted}}{CR}
  3. Step 3 — List the givens: compacted unit weight (gamma_c) = 755.0 kg/m^3, compaction ratio (CR) = 4.8500.

  4. Step 4 — Substitute the given values:

    γl=γcompacted4.8500\gamma_{l} = \dfrac{\gamma_{compacted}}{4.8500}
  5. Step 5 — Evaluate:

    \gamma_{l} = 155.7\ \text{kg/m^3}
  6. Step 6 — Check: returning gamma_l = 155.7 kg/m^3 to

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
\gamma_{l} = 155.7\ \text{kg/m^3}

Why the other options are there

  • 311.3 — kept a factor of two that cancels in the correct rearrangement.
  • 77.8351 — dropped that same factor in the other direction.
  • 171.2 — rounded an intermediate value before the final step.

Reference: FE Handbook — Compaction

Example 10
Compaction — solve for compaction ratio (case 4) — Compaction (10)

compaction ratio of solid waste in a landfill cell Given compacted unit weight (gamma_c) = 920.0 kg/m^3; loose unit weight (gamma_l) = 380.0 kg/m^3, determine the compaction ratio (CR).

Given

  • compactedunitweight(gammac)=920.0kg/m3compacted unit weight (gamma_c) = 920.0 kg/m^3
  • looseunitweight(gammal)=380.0kg/m3loose unit weight (gamma_l) = 380.0 kg/m^3

Find

compaction ratio (CR)

Start with the thinking

  • The governing relation printed in this handbook section is Compaction.
  • Everything except CR is given, so isolate CR symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Compaction of solid waste is characterized by the compaction ratio comparing compacted density to loose density in a landfill.

Step-by-step solution

  1. Step 1 — State the governing relation:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  2. Step 2 — Rearrange symbolically for CR:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  3. Step 3 — List the givens: compacted unit weight (gamma_c) = 920.0 kg/m^3, loose unit weight (gamma_l) = 380.0 kg/m^3.

  4. Step 4 — Substitute the given values:

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}
  5. Step 5 — Evaluate:

    CR=2.4211CR = 2.4211
  6. Step 6 — Check: returning CR = 2.4211 to

    CR=γcompactedγlooseCR = \dfrac{\gamma_{compacted}}{\gamma_{loose}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
CR=2.4211CR = 2.4211

Why the other options are there

  • 4.8421 — kept a factor of two that cancels in the correct rearrangement.
  • 1.2105 — dropped that same factor in the other direction.
  • 2.6632 — rounded an intermediate value before the final step.

Reference: FE Handbook — Compaction

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