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Lab Group Eagles1
In order to run tests, a sample needs to be collected. This sample will be used on all labs for this portfolio.
On the backside of Whitaker Hall at FGCU, towards the boardwalk, there is a bike rack towards the west. Just next to it is a small pit where there is no grass growing. The sample was taken off the surface of this pit.
The sample looks dry by observation, with a light grey-yellow tint. The dirt clumped together in a couple places, but the particles are course enough to visually see. The soil contains the roots and remains of the grass that once grew there.
The sample looks similar to the soils found around homes and smaller buildings. In theory, it would be suitible soil to support smaller structures, but may also support the construction of something larger, like a school.
Specific Gravity is an important characteristic of soil for identification. Soil will typically have a specific gravity value between 2.6 and 2.8. Specific gravity is a ratio of the specific weight of a substance, in this case soil, compared to the specific weight of water.
Calculatios
These are the Calculations used to find e water content and specific gravity of the soil sample
The specific gravity found was 1.839, this is significantly lower than typical SG values of the soil. Organic matter and pore gradation could be factors that lowered the SG this much. In order to continue the lab while being consistant, the SG for the labs will be uped to 2.45.
The water content was low, at 3.19%, but not unreasonably. It would indicate the sample is dry, which makes sense given its location.
The Grain size distribution Lab consists of a sieve analysis and a hydrometer analysis. The purpous of the lab is to identify the size of particles in the soil, as well as the amount of particles at that size.
Hydrometer Analysis
Grain Distribution
Grain Distribution Data
Hydrometer Data
Due to only .31% of the sample was fine grained, the sample must be a course grained soil. Only 9.9% of the sample was gravel, making it a Sand. The low percentage of fine graines make this sample a type of clean sand. With the calculated Cu of 2.99 and CC of .998, the sample has been identified as a porly graded sand.
Compaction is used to increase the overall stress the soil can hold by pushing out the air with water and applied loads. In this lab, multiple tests of varying water connent are used to find the optimal wc for maximum compaction.
The max dry unit weight is 16.69 kN/m^3 at a water content of 5.11%.
The 80% saturation ans ZAV are also plotted on the curve.
Under the assumption that the soil is a sand, the dry unit weight values are initially within the typical values according to Holtz and Kovacs values. It does fall slightly below, but that could be becaus eof the orgnic material or the poor gradation we identiied in previous labs.
The fisrt method of observation are the five senses. Using these senses, we can identify the physical characteristics of soil to identify them. For the smaller grains, a microscope cn be used to assist the eyes in seeing the tiniest details.
Based on Physical Observations, we looked at the characteristics of the soil. There was also a decent amount of organic material found in the sample. Most of it looksed to be dead plants, and the specks of white appear to be lime stone.
The corse particles in the sample all apear around the similar size, with some finer grains found inbetween. They share the same color and texture, which indicates a similar material component in the soil. One of the larger pieces was approximatly .2 mm in diameter, while most were considerably smaller.
Based on the properties to USCS
Classification of soil chart, the fine particles classify as Organic Clay And Silt. There was a lot of material floating in the water, wich would indicate a lower specific gravity. This indicates that Organic Clay and Silt is likely the croorct clasification of the fine graines of the sample.
In the GSD lab, the sample was classified as a poorly graded sand. In the vissual classification, it was identified as organic clay and silt. The main reason for the difference is that the vissual classification only classified the fine grained particles, where as the GSD lab accounted for the predominant coarse grained particles as well. Both classifications can be true, and it is likely that the sample is a poorly graded sand with organic clay and silt.
The hands on approch of these labs really made me get my hands dirty. It is possible to learn about the characteristics of soil through just lectures, but to learn from the labs is an incredible experience. Being able to observe and interact with the properties of soil yourself is more rewarding than reading about it in a textbook.
I am very much a hands on learner. I retain what I learn from a lab more so than what I learn in the classroom. By involving myself in the compaction lab, I was able to feel the importants of adding just the right amount of water for compacting. Too little and the soil would still be loose, too much and the soil would turn to mud. You could learn this from reading, but by handling the soil, you ingrain that feeling into your hands, and the knowledge will stay with you longer.
It is important to note that these labs are connected. The specific gravity found in the lab was required in both the compaction lab and the hydrometer test in the GSD lab. Although the SG value we used was not the calculated value, it was neccesary to keep it consistant or else our results wouldnt match.
Another common component of the lab was how low the water content was throught the lab. The sample also would remain very dry long after being taken out of the oven. The only reason this is noticable is because of the consistancy of using the same sample and building off from previous tests.
The purpose of this lab is to better prepare future engineers. Engineers may not directly involve themselves with labs and testing, but are expected to understand what tests were performed, why was the test done, and what do the results mean. What better way to understand these concepts than by performing the tests ourselves.
The labs also represents how the real world works. Knowing the theory of how soil behaves is very different from working with soil to discover how it reacts. In some cases, experiance will outway knowledge.
Conceptual Map