Report 1 - INTRODUCTION Engineering properties of soils...

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INTRODUCTION Engineering properties of soils vary greatly depending on the soil, and understanding of these properties is highly important prior to embarking on a project within the field of Civil Engineering. Projects such as dam grouting and boring sealant require highly expansive clays, whereas base course for highway pavement calls for well-graded gravel. Tests can be performed in the lab that identifies key characteristics of a soil including particle-size analysis (size and gradation) and the Atterberg Limits (plasticity and water content) tests. Key measurements of particle size include sieve and hydrometer analysis. Mechanical sieve analysis is a relatively quick procedure and gives a detailed representation of the soil’s gradation, given the particle sizes are in the range of .075 to 4.75mm. Important drawbacks of the analysis include a lack of ability to differentiate between particles that are greater or smaller than the range of the test. In response, the hydrometer analysis was developed to find the gradation between silts and clays. In this analysis the soil is suspended in water and the settlement is timed by measuring the change in specific gravity of the remaining suspension. The Atterberg limits are also key characteristics to test for in a fine-grained soil. These tests define how well the soil is able to resist compression and shear forces, as well as the amount of shrinking/swelling occurring. The main three tests performed were the liquid limit, plastic limit, and plasticity index. PROCEDURE The first test was the course-grained particle size analysis, using mechanical sieves. This test began by obtaining approximately 500 grams of air dried soil. This soil was measured using a digital balance, sensitive to 0.1g. A stack of sieves was also obtained and taken apart to be cleaned using various brushes. The sieves were then restacked and the soil was poured into them and shaken using a Ro- Tap mechanical shaker for approximately 10 minutes. Once thoroughly filtered, the contents of each sieve were emptied individually and weighed. These results are recorded and charted on a logarithmic graph. A picture of the Ro- Tap Shaker can be found in Figures and Tables, page 6. The second test was the fine-grained particle size analysis, using an ASTM 152 H hydrometer. 60 grams of soil was obtained and placed in a container. 125 mL of 4% NaPO3 was also obtained and mixed with the soil in an evaporating dish. The mixture was covered with a wet paper towel to prevent evaporation, and set aside for 15 minutes to allow the soil to soak in the solution (it should be noted that the ASTM states to allow for a minimum of 16 hours). While the soil was soaking, another 125mL of 4% NaPO3 was measured and diluted to make
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Report 1 - INTRODUCTION Engineering properties of soils...

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