L03-compaction - 3 Compaction Compaction is the application...

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3. Compaction Compaction is the application of mechanical energy to a soil to rearrange the particles and reduce the void ratio. Table of Contents 1. Purpose of Compaction ..................................................................................... 1 2. Factors affecting Compaction ............................................................................. 1 3. Laboratory Compaction tests ............................................................................. 2 a) Standard Compaction Test AS 1289-E1.1. .................................................... 2 b) Modified Compaction Test AS 1289-E2.1. ..................................................... 2 4. Presentation of Results ...................................................................................... 3 5. Effects of water content during compaction ....................................................... 6 6. Effects of increasing compactive effort ............................................................... 6 7. Effects of soil type .............................................................................................. 7 8. Field specifications ............................................................................................. 8 9. Sands and gravels .............................................................................................. 9 1. Purpose of Compaction The principal reason for compacting soil is to reduce subsequent settlement under working loads. Compaction increases the shear strength of the soil. Compaction reduces the voids ratio making it more difficult for water to flow through soil. This is important if the soil is being used to retain water such as would be required for an earth dam. Compaction can prevent the build-up of large water pressures that cause soil to liquefy during earthquakes. 2. Factors affecting Compaction Water content of the soil The type of soil being compacted The amount of compactive energy used
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3. Laboratory Compaction tests There are several types of test which can be used to study the compactive properties of soils. Because of the importance of compaction in most earth works standard procedures have been developed. These generally involve compacting soil into a mould at various moisture contents. a) Standard Compaction Test AS 1289-E1.1 Soil is compacted into a mould in 3-5 equal layers, each layer receiving 25 blows of a hammer of standard weight. The apparatus is shown in Figure 1 below. The energy (compactive effort) supplied in this test is 595 kJ/m 3 . The important dimensions are Volume of mould Hammer mass Drop of hammer 1000 cm 3 2.5 kg 300 mm Because of the benefits from compaction, contractors have built larger and heavier machines to increase the amount of compaction of the soil. It was found that the
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L03-compaction - 3 Compaction Compaction is the application...

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