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58 Cards in this Set
- Front
- Back
the enlarged size of the footing gives increased _______ ____ between the footing and soil
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contact area
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what reduces the pressure on soil to allowable bearing capacity for soil
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enlarged footing size
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Foundation Design Criteria:
1. _______ properly (horizontal/vertical) 2. safe from _______ ________ failure 3. safe from excessive __________ |
located
bearing capacity settlement |
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criteria for footing to be located properly (vertical/horizontal)
1. _____ action 2. zone of _________ ____ volume change 3. _________ effects 4. __________ defects 5. ________ buildings |
1. frost
2. significant soil 3. groundwater 4. underground 5. adjacent |
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-lifting during cold weather
-dropping during warm weather -footings cannot stand freeze-thaw cycles -place footing below frost line -check building code requirements |
frost action
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-plastic clays shrink and swell greatly
-greatest change near ground surface -foundation below volume zone |
zone of significant soil volume change
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groundwater is
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undesirable
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if there is groundwater, where should you put the footing if possible
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above groundwater
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what reduces soil strength
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groundwater
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hydrostatic uplift from water
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groundwater
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underwater construction is...
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expensive
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if there is groundwater, what may be required
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water-proofing
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faults, caves, and mines are examples of
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natural underground defects
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sewer lines and utility cables are examples of
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man made undergound defects
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soils are subjected to (3)
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compression
tension shear |
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soils STRUCTURAL strength is primarily a function of the soil's...
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shear strength
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the soils ability to resist sliding along the internal surfaces
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shear strength
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the soils ability to resist horizontal movement
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shear strength
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S=
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shear strength
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c=
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cohesion
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effective intergranular pressure is ____________ to shear plane
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perpendicular
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what are the two shear strength parameters
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cohesion
angle of internal friction |
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strength between grains is...
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cohesion
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cohesion is predominantly in
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cohesive soils
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shear strength of a cohesive soil (clay) is related to
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water content
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shear strength of a cohesive soil (clay) is related to the type of
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clay material
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shear strength of a cohesive soil (clay) is related to previous...
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overconsolidation pressure
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angle of internal friction is predominantly in
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granular soils
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angle of internal friction is significant for a ___________ soil
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cohesionless
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interlocking between particles - sum of sliding friction plus interlocking
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angle of internal friction
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sliding friction in a given soil
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angle of internal friction
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interlocking by gradation and density
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angle of internal friction
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angle of repose for soil is related to
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angle of internal friction
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in water, the angle of internal friction is free flowing, so that means it is
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0
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water in voids is driven out during construction /loading due to high permeability
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cohesionless soils
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there is little effect on shear strength due to soil moisture in
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cohesionless soils
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vane test, unconfined compression test, and triaxial compression test are all lab tests for
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shear strength
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in UP, P =
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concentrated load
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p=
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vertical stress at a depth
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z=
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depth
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r=
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horizontal distance
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failure occurs when a definite ______ ____ appears
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failure plane
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failure occurs when a sample has deformed how much
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15%
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Mohr's circle is a graphical representation of
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stress vs strain at failure
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Mohrs circle is a graphical representation of stress vs strain at what
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failure
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the ability of a soil to support a foundation is its
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bearing capacity
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a bearing capacity analysis includes
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shear and settlement failure
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Qult stands for
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ultimate bearing capacity
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the load per unit area to cause shear failure is also known as
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Qult
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Qa stands for
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allowable bearing capacity
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FS stands for
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factor of safety
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after the soil's allowable bearing capacity has been determined you can then determine the
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size of the footing
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Nc, Nq, and Ny are functions of the soils
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angle of internal friction
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Nc stands for
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influence from cohesion
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Nq stands for
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influence from surcharge
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Ny is from the soil's ____ ______ and __________ _____
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unit weight and foundation width
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if groundwater is at a depth of "B" or greater, assume...
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no effect from groundwater
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if water table is at or above the footings base, use the soils _________ ____ ______ for rBNy factor
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submerged unit weight
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