View source for Testwork: Unconfined compressive strength

[[category:Testwork]]
[[category:Geotechnical tests]]
==Testwork: Unconfined compressive strength==
{{Test|name=Unconfined compressive strength|Abrev=UCS|Alt=|F80=100 mm|P80=20 mm|Models=}}

Unconfined compressive strength is a standard measurement of rock competency and is often used to determine rock mass rating (RMR) and slope stability for pit walls.

The test is a 'per-specimen' test where individual specimens of prepared rock are hand-picked by the test operator and placed into the apparatus.  Typically one carefully prepared specimen is chosen to represent a sample and the result reported includes a subjective comment like "good fracture" or "invalid-fracture failure".

===Sample Requirements===

The test requires 1 cylindrical piece of large diameter (typically PQ) drill core, minimum length 150 mm.  

===Test Inputs===

Not applicable.

===Test Outputs===

SAGMILLING.COM uses only metric units of MPa.  If the laboratory reports UCS in other units (such as psi), convert the results before entering.

The laboratory will report the following information:
* <b>N° specimens:</b> The number of specimens tested (typically 1)
* <b>min</b> The value of the specimen with the lowest result (if applicable)
* <b>max:</b> The value of the specimen with the highest result (if applicable)
* <b>stdev:</b> The standard deviation of value of all the specimens (if applicable)
* <b>ucs:</b> The arithmetic average of the UCS in MPa of all the specimens

=== Modelling ===
Unconfined compressive strength is not used directly in any SAGMILLING.COM models.  Literature suggests it can occasionally be used as a proxy for the 
Bond crushing work index if a suitable calibration sample set exists for an ore.  

The UCS reflects the energy requirement to break rocks in the coarse size range, from >100 mm down to about 10 mm - 20 mm.