The Constructor

How to Determine Number of Passes and Lift Thickness for Soil Compaction? [PDF]

How to Calculate number of passes and lift thickness for soil compaction

Reading time: 1 minute

The calculation of the number of passes for compactors and lift (soil layer) thickness for soil is critical to attain the required degree of compaction. Generally, the lift thickness varies between 15-30cm based on soil type, and the majority of compaction is achieved through the first five passes.

One can also use field tests and expertise to determine lift thickness and the number of passes for a specific soil type and condition.

Strip test is one such test that enables engineers to specify the number of passes and machinery type. Additionally, various lift-thickness versus achieved soil density graphs can be used to find the optimum lift thickness and number of passes.

The safety and reliability of buildings and roads are heavily dependent upon the strength of compacted soil below. Improper compaction (non-uniform compaction) may cause building settlements and lead to potholes in roadways.

How to Determine the Number of Passes and Lift Thickness for The Compaction of Soil?

Type of compactorTypes of soilLift thickness, cmNumber of passes
Sheepsfoot rollerFine-grained soil15 4-6
Sheepsfoot rollerDirty coarse-grained soil with more than 20% passing sieve No. 200156-8
Rubber tire rollerClean coarse-grained soil with 4-8% passing sieve No. 200253-5
Rubber tire rollerFine-grained soil or well-graded dirty coarse-grained soil with more than 8% passing sieve No. 20015-204-6
Smooth wheel rollerWell-graded sand-gravel mixtures20-304
Smooth wheel rollerFine-grained soils except in earth dams15-206
Vibrating baseplate compactorcoarse-grained soil with less than 12% passing sieve No. 200, Material with 4-8% passing sieve No. 200 placed thoroughly wet20-253
Crawler tractorCoarse-grained soils with less than 4-8% passing sieve No. 200 placed thoroughly wet25-303-4
Power tamper or rammerSilt or clay10-152
Power tamper or rammerCoarse-grained soils152
Table-1: Lift Thickness and Number of Passes of Different Compactors for Various Types of Soil
Fig. 1: Use Strip Test to Determine Equipment Type and Number of Passes

FAQs on number of passes and lift thickness for soil compaction

How to calculate the number of passes for soil compaction?

The number of passes can be found by strip test and field experience.

What is lifts in soil compaction?

The soil layer that is being compacted is termed as lift.

What is lift thickness?

It is a soil layer thickness that can be properly compacted by compaction machinery. The lift thickness ranges from 15-30cm based on soil type and compaction equipment.

Can you over-compact soil?

No, over compaction creates cracks in soil and decrease its density.

What does it mean to have 95% compaction?

It means that in-situ soil would be compacted to 95% of the maximum dry density. Commonly, the proctor compaction test is used to determine the maximum dry density of soil and its optimum moisture content.

Read More:
Different Types of Soil Compaction Equipments -Types of Rollers
Proctor Soil Compaction Test – Procedures, Tools and Results
Compaction of Soil – Test Methods of Soil Compaction and their Uses
How to Select Compaction Machine Based on Soil Type? [PDF]

Exit mobile version