Sieve Analysis

A H M 531

Seive Analysis

By: Ahmed Essam Mansour

Objective: ¾ ¾ ¾

Determine the particle size distribution of a soil sample by applying the particle size analysis using the mechanical method (Sieve analysis). To obtain the coefficients of uniformity and curvature. To draw the grain size distribution curve.

General discussion: Particle size analysis is the process of determining the relative proportions of the different grain sizes that make up a given soil sample. For coarse grained soil (larger than 0.075 mm) the mechanical method of analysis is done, for grains finer than 0.075mm the Hydrometer method is used for the analysis. For the test appliance a statistically representative sample to reality has to be used, this is obtained by taking a larger amount of the needed soil from different spots of the project under study, and then the reduction of this sample at the lab by the method of quartering and by means of using the riffle box of a proper size. In the experiment we applied the mechanical method which is also known as the sieve analysis. A sieve is an item containing squared openings of specified size, where only the particle smaller than that size can pass through the sieve with proper orientation, sieves are constructed of wire mesh. The test is held by stacking number of standard sieves, ranging in sizes from the largest at top to the smallest, in our experiment the sieves were stacked in the following series; 4.75 – 2 – 1.18 – 0.6 – 0.3 – 0.15 – 0.075 – Pan . Then the sample is thrown into the top sieve and then the set of sieves is placed on a shaker for a period of time. The masses retained on each sieve are measured by means of weighing machine, and from that the Percentage retained is measured by using the formula;

A H M 531 The Civil Engineering Center

And the Percent passing is measured using;

From the obtained results of percentage passing, the grain size distribution curve is drawn on a semi log paper, with the percentage passing representing the ordinate and the sieve size representing the abscissa. The difference in weights of the total sample before sieving and after sieving must not exceed 10% as standards specify, if the loss in mass exceeds that the test shall be repeated with a different sample. From the curve the coefficients of uniformity and curvature are measured using the following formulas;

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A H M 531

Seive Analysis

By: Ahmed Essam Mansour

Knowing the grain size distribution has the benefit of judging the soil suitability for different projects, and of predicting soil-water movement. For example a uniform soil (soil consisting of a small range of size of grains) has high permeability but low strength, the opposite can be seen in a well graded soil (soil containing large range of particle sizes from the smallest to the largest).

Sample identification: The sample tested had light brown color at the beginning, and it consisted from: little amount of gravel, mix of sand size and clay.

Equipments: 1. 2. 3. 4. 5.

Set of sieves (4.75, 2, 1.18, 0.6, 0.3, 0.15, 0.075)mm + Pan Weighing machine. A brush. Riffle box. Shaker

A H M 531 The Civil Engineering Center

Procedures:

1. Weighing 250g (W1) of the oven-dried soil sample, this sample has to be representative to the whole sample; this is accomplished by using the riffle box till the desired weight is obtained. 2. The specimen is washed on sieve #200 to get rid of the grains finer that that sieve (silts and clays), a sieve #10 is place over sieve #200 to retain coarse grains such as gravel, in order to protect sieve #200. The washing process must not contain any loss of the mass due to splashing. This process continues till the water passes through the sieve is clean! 3. The washed specimen is placed in the oven for 24 hours, and the removed and the weight is calculated. W2 4. After stacking the sieves in the order mentioned before the sample is placed on the top sieve, then the set of the sieves is moved to be placed on the shaker for a period of 3 minutes. 5. The sieves are then removed from the shaker and separated carefully, every sieve is re-shacked manually over a pan to make sure that all the grains in that sieve are larger than its size. The passed particles are moved to the smaller sieve. The grains retained at each sieve are weighed.

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A H M 531

Seive Analysis

By: Ahmed Essam Mansour

Calculations: Sample of calculation:

A H M 531 The Civil Engineering Center

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A H M 531

Seive Analysis

By: Ahmed Essam Mansour

Discussion and results: The soil sample we tested is well - graded as can be seen from the graph; where wide range of grain sizes represents a small region of passing percentage. Calculation Cu and Cc was not possible as d10 and d30 was not available on the curve. This indicates that there is a big amount of fines in the sample (50% as can measured from the main mass and the after wash mass). A Hydrometer test shall be applied to determine the coefficients.

A H M 531 The Civil Engineering Center After summing the retained masses on the sieves – to calculate the

percentage of the loss – a weird result was obtained, that is this sum is larger than the total mass sieved. This error was caused by misreading the scale. Sources of error: • Limitations on obtaining a statistically representative sample. • Not providing the suitable orientation for soil grains during shaking in order to pass through the sieves. • Presence of soil lumps. • Errors in reading the weighing scale and zeroing it.

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