Object: Collection of soil samples from the field and preparation of representative soil samples for laboratory testing purposes:
Quartering Method
- Riffle Box Method
Standard: ASHTO-T87-86 BS1377
Apparatus:
a. Quartering | b. Riffle Box |
Straight-edged scoop | scoop |
Flat-edged shovel or trowel | riffles |
Broom or brush | A pair of collection pans |
Theory:
The field samples of aggregate must generally be reduced to an appropriate size for testing to determine physical characteristics, such as sieve analysis, soundness, hardness, etc. The methods described in this test method are intended to minimize variations in the aggregate characteristics between the smaller test sample and the larger field sample. It is, therefore, necessary to reduce field samples while minimizing the chance of variability during handling.
Procedure:
Quartering method:
- Place the original sample on a hard, clean, level surface.
- Mix the material thoroughly by turning the entire sample over with the shovel at least three times.
- With the last turning, shovel the entire sample into a conical pile by depositing each shovelful on top of the preceding one.
- Carefully flatten the conical pile to a uniform thickness and diameter by pressing down the apex with the shovel so that each quarter section of the resulting pile will contain the material originally in the pile. The pile diameter should be approximately four to eight times the thickness.
- Divide the flattened pile into four equal quarters with the shovel or trowel.
- Remove two diagonally opposite quarters, including all fine material. Brush the cleared spaces clean. Successively mix and quarter the remaining material in the same fashion as the original sample.
- Continue this process until the desired quantity is obtained.
Riffle Box Method:
- Place the original sample, or portion thereof, in the hopper or pan and uniformly distribute it from edge to edge being sure the sample appears homogenous (well blended).
- Carefully introduce the sample into the chutes in a manner to allow the aggregate to flow freely through the openings and into the catch pans.
- Continue this procedure until the entire sample has been halved, being careful that catch pans do not overflow.
- Remove the catch pans and set aside. Continue splitting one half of the material.
Follow this procedure, being sure to split entire increments, until the desired test sample size is obtained.
