Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
52 Cards in this Set
- Front
- Back
Why is the saturation of rocks usually less than that of soils? |
Rocks have smaller and less pores and are less permeable than soils bc of compaction and cementation |
|
Preferable rock characteristics |
High sp. Grav, high density, lower absorption |
|
Why low absorption? |
Less freeze thaw |
|
Specific gravity |
Indicates how heavy a rock is compared to an equal volume of water |
|
What does unconfined compressive strength depend on? |
Mineral composition, texture, degree of weathering, degree of saturation |
|
Tensile strength |
1/10 compressive strength |
|
Brazilian test |
Tensile strength, disk of sample is put into a compressive machine and fails from tension as it's squished |
|
Smaller youngs modulus |
More deformation |
|
Straight line on stress v. Strain plot |
Elastic deformation (temporary) |
|
Curved line of stress v. Strain plot |
Plastic deformation (permanent) |
|
What does poissons ratio tell you? |
The direction rock will deform |
|
LA abrasion test |
Measures abrasion resistance and is a strength test |
|
Specs for LA abrasion test |
40% for concrete agg., 45% for base course material |
|
Sulfate soundness test |
Durability test, simulates freeze thaw action of water where the growth of crystals acts as the ice |
|
Sulfate soundness specs |
12% for concrete, 15% for base course material |
|
Absorption test specs |
Aggregate fails if absorption is greater than 3% |
|
Saturation specs |
Passes if S <.85 |
|
Rip rap |
Large stones and boulders used as a protective layer on the upstream face of earth dams or along river banks to protect shores from erosion |
|
Dimension stone |
Stone cut into specific sizes to be used for facing buildings |
|
Flag stone |
Thinly bedded, slab like pieces of rock frequently used in fire places |
|
Strength |
Resistance to failure |
|
Durability |
Resistance to climatic changes |
|
Flat joints |
Joints parallel to foliation |
|
Cross joints |
Perpendicular to foliation |
|
Longitudinal joints |
Strike parallel to the foliation and dip at steep angles |
|
Why is guage dangerous in foundations? |
Impermeable, hinders the movement of ground water and creates distros hydrostatic heads. Can reduce sliding friction in tunnels along fault plane and once sliding occurs, water behind the gauge will flood the tunnel |
|
Popouts and pitting |
Aggregate particles break in half and pop out, many pop outs create a pit |
|
D cracking |
Water percolate through construction joints and high hydraulic pressure from freezing causes cracks |
|
Air entrainment |
Artificially induced air bubbles in cement paste decreases strength but increases durability |
|
Purpose of subsurface investigations |
To find depth, thickness, comp of soil, location of water table, engineering properties of strata |
|
Reconnaissance stage |
To collect as much available info as possible |
|
Exploratory stage |
Drilling and sampling |
|
Auger boring |
Work in dry, moist soils, provide soil for visual examination and basic lab tests |
|
Shelby tube |
Used for deep, undisturbed samples |
|
NX sized diamond bit |
3" outter diameter, 2 1/8" core diameter |
|
What does penetration resistance tell us |
Indicates the density of cohesionless soils and strength of cohesive soils |
|
Spacing of sample holes |
1 hole per 2500 ft ^2 |
|
3 ways stratigraphy controls engineering |
1. Slope angles, 2. More of failure, 3. Drainage |
|
Pre splitting |
Closely spaced holes are drilled and lightly charged, then blasted without millisecond delay and the rock breaks at the desired plane of excavation. Used to minimize overbreak |
|
Shot Crete |
Thick concrete w fine aggregate shot under pressure onto weak rock faces |
|
Spacing of holes for highway investigation |
300 ft |
|
Depth of holes for highway investigation |
6 ft below desired grade and 2/3 max embankment height |
|
Rigid pavement system |
Portland concrete, sub base coyrse, original soil; transfers load through beam action |
|
Flexible pavement |
Asphalt, base course, sub base course, sub grade; load is transferred between particles |
|
Plate load test |
Metal plate is placed on compacted sub grade soil and loaded to 10 psi, settlement in measured |
|
California bearing ratio |
Helps determine thickness of load beating layer of pavement system |
|
Fall |
Travels through air with little to no shear displacement |
|
Topple |
Involved rotational movement, occurs when w/h <tan(theta) |
|
Slides |
Movement occurs along a distinct shear surface or shear zone |
|
Driving forces |
Weight of material, weight of water, weight of structures |
|
Resisting forces |
Shear strength , retaining structures, nailing |
|
7 aspects of discontinuities |
Geometry, continuity, spacing, surface roughness, properties of adjacent rocks, infilling material, presence of water |