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14 Cards in this Set
- Front
- Back
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what effects the engineering properties of granular soils? |
grain size and shape; grain distribution and compactness |
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what are some engineering properties of granular soils? |
1. ability to support large load bearing capacities 2. little settlement 3. good foundation material for roads and structures 4. backfill material for retaining walls, easily compacted and drained 5. exert very little lateral pressures. 6. high schear strengths 7. good embankment material (except in earthen dikes or dams) |
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what are some good engineering properties of cohesive soils? |
1. good for earthen dams and dikes due to low permeability 2. used as a liner for landfills 3. damp proofing |
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What are some undesirable properties of cohesive soils? |
1. low shear strength 2. plastic and compressible, expands when wet, shrinks when dry 3. creeps over time under a constant load 4. develops large lateral forces |
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what are some engineering properties of silt soils? |
fine grained like clay but non cohesive like sand |
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what are some undesirable properties of silt soil? |
high capillary action and susceptible to frost action, yet low permeability and low density |
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what are some engineering properties of organic soils? |
1. none, usually spongy, crumbles, and is compressive. 2. low shear strength
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the first five steps for the field testing of soils (unified system) |
1. remove particles larger than 3" 2. separate all particles larger than #200 sieve. if more than 50% of weight is larger than #200 sieve then it is a coarse-grained soil 3. particles are divided into those that are larger and smaller than 1/4" diameter. if more that 50% of weight is larger then it is considered gravel. otherwise it is classified as sand. 4. if less than 10% weight is smaller than #200 sieve , the second letter is assigned based on the grain size distribution( W= well graded, P= poorly graded) if more that 10% is smaller than #200 sieve , the second letter is based of the plasticity ( L = low plasticity, H= high plasticity) 5. if the sample is fine grained and more than 50% by weight is smaller than #200 sieve, classification is based on dry strength and shaking tests of the material smaller than 1/64" in diameter |
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what are tension cracks? |
usually occur at a distance of .5 to .75 times the depth of the trench, measured from the top of the vertical face of the trench |
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what is sliding? |
occurs as a result of tension cracks. it is a function of soil type and measure |
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what is toppling? |
trenches vertical face separated down the tension cracks and rolls into the trench |
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what is subsidence /bulging? |
an unsupported trench wall can create an unbalanced stress in the soil, causing the surface to subside and bulging of the vertical face of the trench wall |
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what is heaving/squeezing? |
bottom shifting up is caused by the downward pressure created by the weight of the adjoining soil. thus causes a bulge at the bottom of the cut. heaving can occur when shielding is properly installed. |
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what is boiling? |
upward flow of water into the bottom of the cut caused by a high water table. this condition can occur when shielding is properly installed |
