Sieve Analysis And Visual Soil Classification Geotechnical Engineering, Laboratory Experiment #1 1. General Notes All sieves, stations, benches, and tables must be cleaned and returned to their proper location before anyone in your group leaves. DO NOT throw away your sample. Ask the TA what to do with it at the end of the laboratory session. DO NOT share data with other groups or compare data. DO NOT fudge your data to make the results “better”. If there are errors, explain what happened in your report. If you are not sure what happened, provide possible explanations that are logical and use your judgment to determine which one (or more) most likely occurred.
2. Sieve Analysis 2.1 2.2
Enter names of each group member onto the data sheet (attached). Preparatory work 2.2.1 A sample has been prepared for each group. Locate the sample. The sample has been dried in an oven at 110°C (212°F) for 24h to remove all moisture. 2.2.2 Weigh the pan provided (the tare pan), and record the weight on the data sheet. 2.2.3 Weigh the entire soil sample plus the tare pan, and record the weight. 2.2.4 Obtain a stack of sieves. As a minimum, the following sieves should be in the stack, as these sizes are used to classify soils according to the Unified Soil Classification System (USCS) and the AASHTO classification system: #4, #10, #40, and #200. Other sizes should be used to fill in gaps to obtain a total of six to nine sieves depending on the number of sieves that can be used in the shakers available for this test. The stack of sieves should have the largest openings on top and the smallest openings on the bottom, with decreasing size of openings moving from top to bottom. The bottom sieve should be a #200 sieve, with a pan below it to collect all material that passes through it. There should be a lid on the top sieve to keep soil from escaping during the shaking process.
©2007-2012 Bret N. Lingwall, Evert C. Lawton
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Sieve Analysis and Visual Soil Classification
2.2.5
2.2.6 2.3
2.4 2.5 2.6 2.7 2.8 2.8.1
2.8.2 2.8.3
2.8.4 2.8.5
2.8.6 2.9
3.0
Record the sieve sizes and numbers, in order from top to bottom, on your data sheet. You should have between 6 and 10 sieves. Table 2.5 on p. 34 of the textbook (Holtz, Kovacs, and Sheahan, 2011) can be used to determine the size of the screen openings. Usually the size of the openings is also shown on the label for each sieve. See the TA to continue Place the stack of sieves with the lid removed onto the table. Gently pour the ENTIRE soil sample into the stack, so as not to spill any and to keep small particles (dust) from becoming airborne (and thus lost from the sample). Carefully use a brush to get all the fines out of the tare pan and into the stack. Place the lid on the stack of sieves. Ask the TA to help you place the stack of sieves in a shaker. Shake the stack about 10 minutes in a mechanical shaker. Remove the stack from the shaker after the allotted time has elapsed. Tare your tare pan on the scale (make the scale read “0” while pan is on the scale). Weigh the sample Carefully and slowly dump the contents of the TOP sieve only into the pan. Use a brush or metal spatula to remove all particles from the sieve into the pan. DO NOT spill any sample onto the scale or table. Record the weight displayed on the scale on your data sheet. Without removing the soil that is already in the pan or re-taring the pan, gently dump the contents of the next sieve into the tare pan. Clean the sieve as before without spilling any of the soil particles. Some particles may be stuck in the wire mesh. Remove these carefully over the pan so that they fall into the pan. Record the cumulative weights of the material you have removed from the first and second sieves. Repeat steps 2.8.3 and 2.8.4 until all material from the sieves and the pan have been added one by one to your tare pan, recording the total weight of the tare pan after adding material each time. Return the tare pan and the soil sample to the bench top where you obtained them so the next class can use them. CLEAN all sieves, the lid, the pan, and the bench top, and return the stack of sieves in their proper order to the location from which they were obtained. Ask the TA to approve your cleaning of these items and to give your group approval to perform the visual classification portion of this session (see Section 3.0 below).
Visual Soil Classification 3.1
Enter all names of group members onto the data sheet (attached). 3.1.1 A group of samples has been prepared for the class. Locate the samples. The samples have been hydrated for 24h to distribute moisture.
©2007-2012 Bret N. Lingwall, Evert C. Lawton
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3.2
3.3
3.4
4.0
Classification 3.2.1 Observe the first sample at your station. You are encouraged to touch and handle the specimen. 3.2.2 Examine its texture. Make a note of it on your data sheet. 3.2.3 Examine the moisture content of your sample. Is it wet, is it moist, or is it dry? Record your observations. 3.2.4 Examine the color of your sample and make a note of it on your data sheet. 3.2.5 If the sample is granular, estimate the gradation of the sample (well-graded, poorly-graded, gap-graded). Can you determine the gradation? If not, why not? If the sample is cohesive, is the sample “lean” (low plasticity) or “fat” (high plasticity). Record your observations. 3.2.6 What is the probable maximum particle size? 3.2.7 Classify the material into one of the following four general types of soil - gravel, sand, silt, or clay. 3.2.8 Is the sample organic or inorganic? Are there large amounts of roots or other organics present? 3.2.9 Once all the proceeding steps are complete for the first sample, proceed to the next sample and repeat for all the samples at the station. CLEAN bench top and all equipment. Return all equipment neatly to the location from which you obtained them. When the TA has approved your cleaning, he/she will dismiss you. Place all moist samples back into their plastic bags.
Calculations Construct a gradation curve from your sieve data by plotting % Finer on the ordinate vs. Particle Size (in mm) using a logarithmic scale on the abscissa, similar to the curves shown in Chapter 2 of Holtz, Kovacs, and Sheahan (HKS). Use Figure 2.6 on p. 37 as a guide. % Finer means the percentage of the total sample, by dry weight, that is smaller than the particle size corresponding to each sieve. Particle Size refers to the size of the openings in each sieve. Calculate Cu and Cc for your soil sample. Classify your sample using the USCS method. Assume the soil is non-plastic. Classify your sample using the AASHTO method. Classify all the visual samples from Section 3.0 by USCS as best you can (estimate LL and other parameters as necessary) using ASTM D-2488: Description and Identification of Soils (Visual-Manual Procedure) for guidance. All calculations must conform to departmental report guidelines (Laboratory Handout 3). Present calculations in the Results section of your report.
©2007-2012 Bret N. Lingwall, Evert C. Lawton
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5.0
Questions Answer all questions in the discussion portion of you laboratory report. Discuss the gradation of your sample. For example, is it well graded, poorly graded, or gap-graded? Why? Can the sieve analysis be done on a moist sample? Explain why or why not. Would this soil be a good bearing material to support the foundations of a building? Explain why or why not. Would this soil be a good subgrade material on which to construct a paved road? Explain why or why not. Discuss differences in the classifications obtained from the AASHTO and USCS methods. How would a PL > 0 and a LL > 0 affect the classification? When would you need to classify a soil using the visual-manual procedure? Of the soils you observed in the visual classification portion of this laboratory session, which would be the best to use as a foundation material where high strength and low compressibility are the most desirable properties? Which would be the best to use as a cap for a landfill where low permeability and flexibility are the most desirable properties? Discuss.
©2007-2012 Bret N. Lingwall, Evert C. Lawton
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Sieve Analysis and Visual Soil Classification
Sieve Analysis Data Sheet Group Member Names:
Tare name = Tare Weight =
grams
Dry Soil + Tare =
grams
Dry Soil Weight =
grams
Sieve Size or Sieve # EXAMPLE:
#200 PAN
#10
Sieve opening Cummulative Size Weight Retained (mm) (g) 2.00
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©2007-2012 Bret N. Lingwall, Evert C. Lawton
20.32
Percent Passing (%) 3.60
NA
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Visual Soil Classification Data Sheet Group Member Names:
Test Date:
Specimen Number
Color
Moisture
©2007-2012 Bret N. Lingwall, Evert C. Lawton
Soil Type
Notes
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Photographs Courtesy of Susan E. Burns and Georgia Institute of Technology © 2006 Board of Regents of the University System of Georgia Sieve Analysis
These photographs can be viewed at larger scale from the JPG files included in the ZIP file for this laboratory experiment.
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