Wet Sieve Analysis
Wet sieving analysis of soils is used to analyze particles that contain large amounts of silt and clay. The soil particles are washed to ensure that the fine-grained particles are separated from the coarse-grained ones. The extremely fine particles normally clump together and have difficulty in passing the # 200 sieve. In this experiment, the classification of soils is done in order to determine the percentage of soil particle that passes the # 200 sieve. The Wet analysis is used to determine the fine particles in the soil sample (“45Th Anniversary of The Journal, 16)
Materials
Mortar and pestle
Mechanical shaker
Squeeze bottle with water
Evaporating dish of 8 inches in size
Two evaporating dishes of four inches each
Sieves of sizes (# 10, 40, 60, 140 and 200, pan and lid)
Wire sieve brush (for sieves larger than # 60)
Paint brush (for sieves # 60 and smaller)
Drying oven
Balance that is accurate to 0.1 grams
High clay content soil.
Procedure
A soil sample of approximately 300 grams is obtained and pulverized until there are no more clumps in it. Care should be taken to avoid crushing rocks in the mortar. The sieves are then cleaned, and the weight of each sieve and pan is obtained. The sieves are stacked from the largest to the smallest. i.e. #200-#10. The soil sample is then placed on the top sieve and covered with a lid. The sieves are placed in the nest of sieves and mechanically shaken for six minutes. Finally, the sieves are weighed, and all the material is discarded except for the material that remained on the #200 sieve. The # 200 sieve is rinsed in the sink with water above the 8-inch evaporating dish until the water leaving the sieve is clear. This is followed by collection of the sample that was left on the edges of the sieve and weighing of the evaporating dish. The soil sample is washed into the evaporating dish from the water in the squeeze bottle. The evaporating dish is then placed in the drying oven, and the weight of remaining sample is determined.
Results
The following equations were used to fill Table 1 below.
Equation 1 is used to calculate the percent of mass retained
Rn=WnWts x 100 1
Where,
Rn = % retained on individual sieve
Wn = Mass on individual sieve
Wts = Mass of total sample
Equation 2 is used to calculate the weight the cumulative percent retained on each successive sieve in the 7th column, table 1.
Cumulative % retained = i=1i=nRn . 2
Equation 3 is used calculate the percent finer for the 8th column in Table 1
% finer = 100 - i=1i=nRn 3
In analysis of the total mass lost during analysis, equation 4 is used
Mass lost during analysis (%) = 100(Wi – Wts)/ Wi 4
Where Wi = initial sample mass
Wf = Wpan + W#200 - Wd . 5
Where, Wpan = mass retained on the pan
Graph
Equation 5 is used to calculate the coefficient of uniformity in the particle size distribution
Cu = D60/D10 .. 6
Where,
Cu = Coefficient of uniformity
D60 = maximum diameter of particles finer than 60%
D10 = maximum diameter of particles finer than 10%
D60 = 3.3 mm
D10 = 5.6 mm
Therefore, Cu = 3.3/5.6 = 0.589
Equation 6 is used to calculate the coefficient of curvature
Cc =D30 2D60 x D10 . 7
Where,
Cc = Coefficient of curvature
D30 = maximum diameter of particles finer than 30%
D30 = 5.0mm
D60 = 3.3 mm
D10 = 5.6 mm
Therefore, Cc =5.0 25.6 x 3.3 = 0.842
Atterberg Limits
This is a method of classifying soils by determination of the moisture content. It comprises of two tests; liquid limit and plastic limit test. Plastic limit determines the lowest moisture content at which the soil is plastic. Liquid limit, on the other hand, is a term referring to a point where the soil water content changes it from plastic to liquid state. This experiment determines the properties of soil using liquid limit and plastic limit test.
Materials
Sieve # 40, pan and lid
Wire brush (for sieves larger than # 60)
Mortar and pestle
Casagrande LL device (B)
Casagrane cup (A)
Grooving tool (D, E)
Eight moisture cans
Spatula
Squeeze bottle with water
Glass plate (C)
Eight inches evaporating dish
Two four inch evaporating dish
Drying oven
Balance accurate to 0.1 grams
Atternberg soil
Procedure
The plastic limit experiment is conducted first because most soils have lower plastic limit than the liquid limit.
Plastic Limit
A sample of 250 grams with particles finer than # 40 sieve is obtained. Eight moisture cans are weighed and marked. An approximate half of the soil sample is slowly added water until it is stiff and has a putty-like consistency. An ellipsoid is then rolled on a glass plate into a cylindrical thread and approximately 0.5 inch in diameter. The above steps are repeated, and the average of PL is evaluated. The moisture content is obtained when the thread breaks at one-eighth inch diameter. The cracking beyond one-eighth of an inch shows that the soil sample is to dry but below one-eighth and cannot crack, the sample is too wet (“45Th Anniversary of The Journal, 16)
Results
Equation 6 below is used in determination of plastic limit (PL) from the experiment
PL= Wm-WdWd-Wc x 100 .. 6
Where
Wm = weight of the can and the moisture sample
Wd = weight of the can and the dry sample
Wc = weight of the can.
(“45Th Anniversary of The Journal, 16)
Liquid Limit
The Casagrande device is cleaned tested and calibrated. The cup should fall exactly one cm onto the base. A small amount of water is added to the sample, and the Casagrande Cup is filled to a depth of 10mm. A spatula is used to smoothen the surface of the sample. A trench is then formed in the center of the sample using the grooving tool. After preparing the sample, the crank is turned at 2rotations per second and is stopped when the gap in the soil is closed. Finally, the number of drops (N) is recorded and the moisture content obtained. At least four values of N are needed for interpolation.
Results
The following conditions apply:
If N>35, the soil is too dry
N<15, the soil is too wet
(“45Th Anniversary of The Journal, 16)
The liquid limit from the graph is the moisture content at 25 drops. This gives 48 % when a straight line best-of-fit is (red) chosen.
At N=25, the liquid limit can be obtained using equation 7
LL=ωNN250.121 .. 7 (“45Th Anniversary of The Journal, 16)
Where, ωN = the moisture content of the sample.
LL=4825250.121
= 1.597
FI= ω1-ω2logN2-logN1 8
This is similar to finding the slope of the graph
FI= 49.3-47.25log29-log18
= 9.897
Discussion
According to AASHTO system of soil classification, the particle size of the soil is used to determine the soil fraction. From the previous experiment on dry sieve analysis, the values were as follows
D60 = 3.3 mm
D30 = 5.0 mm
D10 = 5.6 mm
Therefore, Cu = 3.3/5.6 = 0.589
And the coefficient of curvature = 0.842
The soil in the fraction of coarse sand and can be used for construction (Engineeringcivil.com, 20)
According to USCS standard, we use the PL and LL to classify the soil. From the experiment, the LL is 1.597 while the PL = 9.897. From the Casagrande’s plasticity chart, the soil falls under a category of silty clays, clayey silts, and sands. This class of soils is good for foundation, and the client can go ahead in construction (Engineeringcivil.com, 23)
Conclusion
This experiment was done through the separation of soils according to their sizes using sieves of various sizes to. Two major characteristics of soil were determined; the liquid limit and the plastic limit. The two values classified the soil suitable for construction due its low plasticity and liquid limit. This was based on AASHTO and USCS standards.
Some errors that might have been in the experiment were due to lack of inconsistency in values. This could be seen as a result of faulty equipment, ordinary blunders, and few trials. The same can be resolved via frequent and careful doing of the same experiment, ensuring error-free equipment and avoiding obvious mistakes. In short, the experiment was done to satisfaction.
Work Cited
Engineeringcivil.com, "Various Lab Test on Soil". N.p., 2011. Web. 22 Feb. 2016.
"45Th Anniversary of The Journal "Soil Mechanics And Foundation Engineering" ("SMFE")". Soil Mechanics and Foundation Engineering 41.1 (2004): 1-3. Web.
Abdaal, A., G. Jordan, and P. Szilassi. "Testing Contamination Risk Assessment Methods for Mine Waste Sites". Water, Air, & Soil Pollution 224.2 (2013): n. pag. Web.
Appendix I
USACE EM_1110-1906 Appendix V [3]
ASTM 421 [7]
Appendix II
USACE EM_1120-2-1906 Appendix III [3]
ASTM D4318-10e1 [9]
