Determination of length to thickness ratio of armor stone test.
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Determination of length to thickness ratio of armor stone test.

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Determination of length to thickness ratio of armor stone test.


Principle.

The individual pieces of armor stone shall be classified on the basis of their maximum length L and minimum thickness T, as determined by visual inspection by using straight laths and carpenter’s rule or a tape- measure or by using a caliper.

Preparation of test portion.

The sample shall be taken and reduced if necessary in accordance with the requirements of clause 4 to produce the required test portion. Fragments shall be discarded.

Test portions obtained for the determination of the mass distribution of a light and heavy grading may be used for this test. Each stone in the test portion shall have the weight above the extreme lower limit (ELL) of the designed grading class. The number of pieces of armor stone for the testing may vary from minimum 25 to 200 with different grading class.

Procedure.

Measure the length (L) of each stone as the maximum distance between tow portions on the stone and measure the thickness (T) of each stone as the minimum distance between two parallel straight lines through which the stone can just pass. The tape measure, caliper, or carpenter’s rule shall be used for measuring length and thickness.



Take the total weight and total number of the stone with a length- thickness ratio of greater than 3.

Calculation and expression of the results.

For heavy grading, calculate the percentage ,X, of pieces of armor stone with a length/ thickness ratio greater than 3.

X = N1 /N2 * 100

Which,

N1 is the number of pieces of armor stone with a L / T ratio greater than 3.

N2 is the total number of pieces of armor stone tested.

For light grading, calculate the percentage ,X, of pieces of armor stone with a length/ thickness ratio greater than 3.

X = M1/M2*100

Which,

M1 is the total mass of pieces of armor stone with a L / T ratio greater than 3 (kg).

M2 is the total mass of pieces of armor stone tested.

References.

The rock manual, CIRIA C 683 : 2007/ BS EN 133-2:  2013.

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