Linear Shrinkage Test Free Essay Example

AIM: To determine the linear shrinkage likely to be experienced by clay material

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THEORY: Linear shrinkage is the decrease in length of a soil sample when oven-dried, starting with a moisture content of the sample at the liquid limit.

This test is used to measure the percentage decrease in dimension of a fine fraction of a soil when it is dried after having been moulded in a wet condition approximately at its liquid limit. The linear shrinkage is found by determining the change in length of the semi-cylindrical bar sample of soil when it dries out, starting from its liquid limit or near the liquid limit. This test gives the percentage linear shrinkage of a soil and it can be used for the soil of low plasticity including silts, as well as for clays.

LIST OF EQUIPMENT/ APPARATUS:

Drying Oven

(UTEST, Prod no.; UTD-1305, Serial no.; 15/002183, 95kg, 250lt, 80*85*102cm),

Weighing Balance

(Dikomsan, Model; JS 30 BH, S/N;140812, Min/Max=0.5/30Kg, Temp. 0-+40 °C),

Mixing Pan,

A Flat Glass Plate,

Airtight container,

Wash bottle filled with distilled water,

Spatula,

Gloves,

Trowel,

Brass Mould for Linear Shrinkage,

Vernier Caliper,

Petroleum Jelly,

Soil sample collector.

DIAGRAMS:

Drying Oven Weighing Balance Mixing Pan

Mould Spatula Soil Sample Collector

Trowel Gloves A Flat Glass Plate

Vernier Caliper Wash Bottle Petroleum Jelly

PROCEDURE:

Cleaned the mould thoroughly and applied a thin film of petroleum jelly to its inner faces to prevent the soil adhering to the mould.

Took the soil paste sample at approximately the liquid limit.

Placed the soil/water mixture in the mould such that I slightly proud of the sides of the mould. Gently Jared the mould or carefully taped the mould against a firm surface, to remove any air pockets in the mixture.

Levelled the soil along the top of the mould with the spatula and removed all soil adhering to the rim of the mould by wiping with a damp cloth.

Placed the mould where the paste air dried slowly for l-2 days until the soil shrunk away from the walls of the mould.

Then completed the drying at 105°C to l 10°C in the Drying Oven.

Cooled the mould and measured the mean length of the soil bar by pressing it against the end of the mould where there was a better fit, while measuring the distance between the opposite side of the mould and the soil bar.

RESULTS:

LO = 140mm

LD = 130mm

CALCULATION:

LO = Initial Length of sample

LD = Length of oven dried specimen

Percentage of Linear Shrinkage = ( (Lo- LD )/Lo x 100%)

( (140- 130)/140 x 100%) = 7.14%

DISCUSSION:

We took the soil sample at an approximate penetration close to the Liquid Limit as 21.7mm, Using the Vernier calliper for accuracy, measured the length of our mould as our initial length, and length of the oven dried specimen.

CONCLUSION:

Experiment was successfully concluded and the Percentage of Linear shrinkage calculated as the difference between the initial length and oven dried length to the initial length, expressed in percentage to be 7.14%

PRECAUTIONS:

Zeroed my scale before taking my readings

Avoided parallax error while taking my readings

Avoided loss of sample after taking the measurements

Made sure no sample fell on the balance while taking my measurements

Made sure the penetration stopped at 5 seconds

Made sure the moisture cans contained at least 6 grams of soil