lab report 3

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Civil Engineering

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Apr 3, 2024

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Georgia Institute of Technology School of Civil and Environmental Engineering Atterberg Limits Laboratory MEMORANDUM To: Emre Duman Date: February 15, 2023 From: Sachinshripadh Dasu, A3-1 Lab Partners: Stephen Grafius, Marty Robert James Jr., Ashley Eun Joo Jhun Subject: CEE 3400 Sample(s) Description: Name: Piedmont Red Clay Source: In-Situ Condition: Dry Visual Classification and Unified Symbol: SM Remarks: Piedmont Red Clay was used as a soil sample for this laboratory experiment. Test Procedure: Test Procedures: ASTM D4318: Standard Test Method for Liquid Limits, Plastic Limit, and Plasticity Index of Soils The Atterberg Limits laboratory is based on ASTM standard ASTM D4318. Atterberg Limits are some of the most important and basic index properties of fine-grained soils. Atterberg limits are therefore used to classify soils via the USCS. The Atterberg limits are the liquid limit, the plastic limit, and the shrinkage limit. Each Atterberg limit is a water content value that defines transition boundaries in soils. The liquid limit test is a type of dynamic shear test, and the liquid limit typically corresponds to a shearing resistance of 1.7 to 2.0 kPa. The plastic limit corresponds to a strength of approximately 170 to 200 kPa. The value for the liquid limit can vary tremendously between soils, from approximately 20% for silts, all the way up 900% for Montmorillonit. The liquid limit is controlled by the specific surface of the soil, with more water required to weaken the soil with a higher specific surface. The Casagrande cup works on principles of slope stability. The Fall Cone test is based on principles of soil bearing capacity and undrained shear strength variation as a function of water content. The Atterberg Limits laboratory consists of two parts. Part 1 is the Liquid Limits (Fall Cone Part 1: Liquid Limits Test via the Fall Cone Test) and Part 2 is the Plastic Limit Test (where Part 2A is the Thread-Rolling Test and Part 2B is the Fall Cone Test). In Part 1, 400-500 grams of the soil sample is mixed with deionized water to form a paste that is then placed in the Fall Cone cup. Then, after adjusting the apparatus, the initial reading on the travel gauge is recorded and then the test is repeated for three trials. These trails are repeated to get two points above 20 mm and two points below 20 mm. In Part 2, the moist soil sample is molded into an elongated pat with an 1/8 inch diameter thread. The sample is rolled out until it crumbles at a thread of 1/8 diameter in order to determine 3 plastic limit values that can be averaged.

Test Results: 1. The graph below, Figure 1. Travel Distance Vs. Water Content, provides the liquid limit of the soil type using the Fall Cone Test method on the appropriate log scales. 10 100 10 20 30 40 50 60 70 80 90 100 f(x) = 0.48 x + 47.66 Travel Distance (mm) Water Content (%) Figure 1. Travel Distance Vs. Water Content The liquid limit of the soil type is calculated using the equation for the line of best fit (which is the trendline and corresponding trendline equation shown in the graph above). This corresponds to a travel distance of 20 mm and to then calculate the water content. The plastic limit is also calculated below based on the Fall Cone method first, as well as by the Thread- Rolling Test. Sample calculations are shown below for the water content percentage as well as the plastic limit by both test methods. Water Content (%) = 0.4846(x) + 47.655 Water Content (%) = 0.4846(20) + 47.655 Water Content = 57.347% = Liquid Limit Plastic Limit (Fall Cone Test) = C*(2 m ) C = Y-Intercept = 47.666 m = 0.4846 Plastic Limit = 47.655*(2 .4846 ) Plastic Limit = 66.679% This water content percentage (57.347%) corresponds to the liquid limit of the soil sample. Plastic Limit (Thread-Rolling Test) = Average Water Content Plastic Limit = 38.67% Analysis and Discussion: The Atterberg Limits laboratory is based on ASTM standard ASTM D4318. Atterberg Limits are some of the most important and basic index properties of fine-grained soils. Atterberg limits are therefore used to classify soils via the USCS. The Atterberg limits are the liquid limit, the plastic

limit, and the shrinkage limit. Each Atterberg limit is a water content value that defines transition boundaries in soils. The liquid limit test is a type of dynamic shear test, and the liquid limit typically corresponds to a shearing resistance of 1.7 to 2.0 kPa. The plastic limit corresponds to a strength of approximately 170 to 200 kPa. The value for the liquid limit can vary tremendously between soils, from approximately 20% for silts, all the way up 900% for Montmorillonite. The liquid limit is controlled by the specific surface of the soil, with more water required to weaken the soil with a higher specific surface. The Casagrande cup works on principles of slope stability. The Fall Cone test is based on principles of soil bearing capacity and undrained shear strength variation as a function of water content. The Atterberg Limits laboratory consists of two parts. Part 1 is the Liquid Limits (Fall Cone Part 1: Liquid Limits Test via the Fall Cone Test) and Part 2 is the Plastic Limit Test (where Part 2A is the Thread-Rolling Test and Part 2B is the Fall Cone Test). The experimental procedures that are utilized in this laboratory are reliable and easily replicable as they are useful in classifying soil samples. The fall cone test is a reliable procedure to calculate and determine the plastic and liquid limits. The thread-rolling test is not as reliable as there is a degree of human perception when collecting data, therefore the Fall Cone test is more reliable as a procedure to determine those limits. However, a combination of these tests can be useful and reliable to determine a range for these values. Three sources of error in this laboratory are human error with the thread-rolling test, conducting repeat trails in the fall cone test, and human error with the fall cone test. With the thread- rolling test, the human error can be accounted to the human perception of 1/8 inch diameter of the threads and crumbles. The threads could have not been 1/8 inch exactly, causing the water content percentage to vary based on these differences. Conducting repeat trails with the fall cone test can cause errors with calculating the correct water content of the soil samples. These repeated trails can cause rounding error when collecting values on the fall cone apparatus. Human error with the Fall Cone test can also be accounted to timing errors with waiting 5 seconds after dropping the cone, rounding error when reading measurements, and aligning the equipment exactly on the surface of the soil sample without affecting the soil sample prior to dropping the cone. Potential engineering applications of the Atterberg Limits laboratory are determining load capabilities of soils. This can be used to design foundations of buildings. It can also be important to use on soils near bodies of water to better understand the types of structures that can be safely built on those lands. 1. There is significant operator dependence on the Casagrande Cup and Fall Cone test that can affect the reliability of the test. There are also several advantages and disadvantages of each test. For the Casagrande Cup test method, there is significant operator dependence as the force of the blows could be slightly different, causing error in collecting and calculating the data. The tuning of the crank, as well as having different operators perform blows could cause significant error and affect the reliability. For the Fall Cone test method, there is significant operator dependence as the set up of the apparatus could vary between operators. This is mainly shown with setting the cone on the surface of the soil, as well as holding the cone down for 5 seconds, the time of which could vary slightly between operators and trials. This operator dependence is slightly lower than with the Casagrande Cup test method. The main advantage of the Casagrande Cup method is that it is a test method that can be easily applied in the field. The disadvantage is the reliance on operator dependency as it can be difficult to determine when to stop delivering blows when the soil is touching the grooves. The main advantage of the Fall Cone test is that it is less operator dependent and that the results are more reliable than the Casagrande Cup test method. The disadvantage of the Fall

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