Question

In soil compaction test, if test result exceeds 100%, should engineers accept result?

Answer

Soil compaction is method of increasing soil density by reducing volume of air within soil mass.
Soil compaction depends mostly on degree of compaction and amount of water present for lubrication. As a rule 2.5kg rammers and 4.5kg rammers are accessible for compaction in laboratories and maximum dry densities produced by these rammers cover range of dry thickness obtained by in-situ compaction plant.

Regarding second factor of water content, it affects compaction in following ways. In low water content, soils are difficult to be compacted. While water content is increased gradually, water will lubricate soils and this facilitates compaction operation. Yet, at high water content, as a growing proportion of soils are occupied by water, dry density decreases with an enhancement in water content.

For soil compaction tests, dry density obtained from compaction approved out in-situ by vibrating roller or vibrating plate is compared with maximum dry density conducted in laboratories using 2.5kg rammer of compaction with alike soils. In essence, in-situ compaction is compared with compacting effort of using 2.5kg or 4.5kg, rammer in laboratories. In case compaction test results indicate values exceeding 100%, it only way that in-situ compaction is additional than that being passed out in laboratories that is treated as basic criterion for acceptable degree of soil compaction. So, soil results are acceptable in case compaction test results are in excess of 100 per. though, excessive compaction poses a risk of fracturing grainy soils resulting in reduction of soil power parameters.