Experiment No. 10: Soil Unconfined Compressive Strength
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Determination of unconfined compressive strength of a clayey soil either in undisturbed or remoulded condition.

Compression machine, Proving ring, Deformation dial gauge, Timer, Sampling tube, Specimen extruder, Split mould, Specimen trimming tools, Vernier calipers, Balance, Apparatus for moisture content determination.

1. Prepare the test specimen, which may be either undisturbed, remoulded or compacted. Undisturbed specimens can be carved from a large soil block, or obtained through a sampling tube from which the specimen can be extruded to a split mould using a sample extruder.

2. Trim the two ends of the soil specimen, remove it from the mould, and measure the length, diameter and weight.

3. Place the specimen on the bottom plate of the compression machine, and adjust the upper plate to make contact with the specimen. Initialize the vertical displacement gauge and proving ring gauge to zero. Select an axial strain rate between 0.5% to 2.0% per minute and apply compression load.

4. Record the load and displacement readings at every 20 to 50 divisions of displacement gauge, or at every 15 seconds.

5. Compress the specimen till the load peaks and then falls, or till the vertical deformation reaches 20% of the specimen length.

6. Remove the specimen from the machine, and take soil samples for water content determination.

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