Chapter: Earthworks Civel engineering engineer doubt problem guide and intrview questions and answer
In soil compaction test, if a test result exceeds 100%, should engineers accept the result?
In soil compaction test, if a test result exceeds 100%, should engineers accept
the result?
Soil compaction is the process of
increasing the soil density by reducing the volume of air within the soil mass.
Soil compaction depends mainly on
the degree of compaction and the amount of water present for lubrication.
Normally 2.5kg rammers and 4.5kg rammers are available for compaction in
laboratories and the maximum dry densities produced by these rammers cover the
range of dry density obtained by in-situ compaction plant.
Regarding the second factor of
water content, it affects the compaction in the following ways. In low water
content, the soils are difficult to be compacted. When water content is
increased gradually, water will lubricate the soils and this facilitates the
compaction operation. However, at high water content, as an increasing
proportion of soils is occupied by water, the dry density decreases with an
increase in water content.
For soil compaction tests, the
dry density obtained from compaction carried out in-situ by vibrating
roller/vibrating plate is compared with the maximum dry density conducted in
laboratories using 2.5kg rammer of compaction with similar soils. In essence,
the in-situ compaction is compared with the compacting effort of using 2.5kg (or
4.5kg) rammer in laboratories. In case the compaction test results indicate
values exceeding 100%, it only means that the in-situ compaction is more than
that being carried out in laboratories which is treated as the basic criterion
for satisfactory degree of soil compaction. Therefore, the soil results are
acceptable in case compaction test results are over 100%. However, excessive
compaction poses a risk of fracturing granular soils resulting in the reduction
of soil strength parameters.
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