Compaction
Environmental Engineering · FE Reference Handbook section
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.
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for CR:
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.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning CR = 2.4750 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for gamma_c:
Step 3 — List the givens: loose unit weight (gamma_l) = 295.0 kg/m^3, compaction ratio (CR) = 4.6000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
\gamma_{c} = 1357\ \text{kg/m^3}Step 6 — Check: returning gamma_c = 1,357 kg/m^3 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for gamma_l:
Step 3 — List the givens: compacted unit weight (gamma_c) = 910.0 kg/m^3, compaction ratio (CR) = 4.7500.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
\gamma_{l} = 191.6\ \text{kg/m^3}Step 6 — Check: returning gamma_l = 191.6 kg/m^3 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for CR:
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.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning CR = 3.7200 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for gamma_c:
Step 3 — List the givens: loose unit weight (gamma_l) = 200.0 kg/m^3, compaction ratio (CR) = 4.2500.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
\gamma_{c} = 850.0\ \text{kg/m^3}Step 6 — Check: returning gamma_c = 850.0 kg/m^3 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for gamma_l:
Step 3 — List the givens: compacted unit weight (gamma_c) = 515.0 kg/m^3, compaction ratio (CR) = 2.6500.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
\gamma_{l} = 194.3\ \text{kg/m^3}Step 6 — Check: returning gamma_l = 194.3 kg/m^3 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for CR:
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.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning CR = 6.4444 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for gamma_c:
Step 3 — List the givens: loose unit weight (gamma_l) = 355.0 kg/m^3, compaction ratio (CR) = 4.9000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
\gamma_{c} = 1740\ \text{kg/m^3}Step 6 — Check: returning gamma_c = 1,740 kg/m^3 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for gamma_l:
Step 3 — List the givens: compacted unit weight (gamma_c) = 755.0 kg/m^3, compaction ratio (CR) = 4.8500.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
\gamma_{l} = 155.7\ \text{kg/m^3}Step 6 — Check: returning gamma_l = 155.7 kg/m^3 to
reproduces the given quantities, and both sides carry the same units.
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
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
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
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for CR:
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.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning CR = 2.4211 to
reproduces the given quantities, and both sides carry the same units.
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