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26 Cards in this Set
- Front
- Back
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What are 3 Engineering properties of Soil? |
Permeability, Consolidation, Shear Strength |
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What are 4 factors that affect permeability |
1) Size/Shape/Uniformity of soil particles 2) Fluid Type 3) Degree of Saturation 4) Pressure Head Difference |
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Define One Dimensional/Two Dimensional Flow |
One Dimensional- When velocity vectors are all parallel and of equal magnitude Two Dimensional- All velocity vectors are confined in a single plane but vary in magnitude and direction |
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What are the two flow types (scale) and define what it means. |
1) Macroscopic- Assumed to be a straight path 2) Microscopic-Travels through winding path through voids |
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When do we use constant head test vs. falling head test? |
Constant head test determines hydraulic conductivity for coarse soils,gravels Falling head test is for fine grained (clays/silts) |
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What does Laplace Equation describe (its main principle)? |
That there is energy loss as water travels through a medium |
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What are 5 assumptions for Laplace Equation? |
1) 100% saturation 2) Constant hydraulic conductivity (homogeneous soil) 3) Incompressible soil/water 4) No consolidation/expansion of soil 5) Laminar flow of water |
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Steps in drawing a proper flow net diagram |
1) Draw a scaled cross section of the situation 2) Draw flow lines 3) Draw equipotential lines 4) Make sure ratio of a to L is equal. In other words, make sure the shape can fit a circle. |
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What are 3 major types of structures? |
1) Gravity Impervious 2) Gravity permeable 3) Sheet pile wall |
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What is the safety for uplift and what are its limits. |
F.S is (Wstructure/Uplift force) >= 1.5->2 |
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Explain why hydraulic gradient isn't equal |
Hydraulic gradient is h/L. L changes depending on size of curvelinear square. Smaller square means lower L and higher gradient. |
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What happens when you reduce sheet pile wall penetration? |
Less equi drops means h/Nd is a higher value, and so you have higher values for hydraulic gradient. So you get closer to icritical. |
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Define quick condition |
No contact stress between soil particles |
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How would you prevent quick condition? |
You prevent it by building/installing filters. 1) Graded soil filters (d85 and d10 prevent soil movement past filter) 2) Geotextile |
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What is piping? |
The removal of soil particles along the path of seepage. Results in a pipe like feature along path. |
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What is heaving? |
Upward movement of soil particles due to high seepage gradient near exit flow. |
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What are 4 improvements due to soil compaction? |
1) Increase shear strength 2) Decrease Compressibility\ 3) Decrease hydraulic conductivity (k) 4) Decrease void ration (e) |
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What are the standard proctor test specifications (e.g hammer, layer #) |
-5.5 lb Hammer - 12 in hammer drop - 3 layers compacted 25 blows. Total of 75 blows |
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What are the Modified proctor test specs (e.g hammer, layers) |
-10lb Hammer - 18 in hammer drop - 5 layers compacted 25 blows. Total of 125 blows |
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Why is it better to start of with a dry soil when checking compaction? |
Because you are able to control water content easily. With wet, you will need to dry beforehand |
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Disadvantage of too much water in soil regarding compaction? |
Too much water means little to no air left in voids, becomes harder to compact. There is also too much pore pressure. |
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Disadvantage of too little water in soil regarding compaction? |
Too fluffy. Soil will resist compaction via shear strength, friction. |
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What are the 4 field density testing methods? |
1) Sand cone 2)Balloon Densometer 3) Shelby Tube 4) Nuclear guage |
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Describe how the Nuclear Densometer works |
Isotope (cesium-134) releases photons. Dense soil absorbs more radiation than loose soil and readings reflect overall density |
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When would you want to be on the wet side of the optimum water content? |
When you want to resist seepage and prevent cracking. Soil strength is NOT your top priority. |
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When would you want to be on the dry side of the optimum water content? |
When you want high soil strength. |
