Engineering Geology Test 1 – Flashcards
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Define Engineering Geology
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The science of geology applied to environmental and engineering concerns, including the safety and performance of man-made structures, and to public health, safety, and welfare.
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Define Geological Engineering
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The engineering discipline specializing in the evaluation and design of engineering projects, in or on the earth and the evaluation of earth materials.
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What are Geological engineers work typically involves
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Mining Petroleum recovery Civil engineering And deal with design and performance of the project
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Compare a engineering geologist and geological engineer.
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The engineering geologist is a geologist with a strong awareness and understanding of engineering and engineering principals The geological engineer is an engineer with a string awareness and understanding of geology and geologic principals.
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Engineering Geology includes
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•describing and evaluating subsurface geologic structures, stratigraphy, and water conditions affecting the things humans build; •exploring and developing rock, soil,and water resources; •evaluating natural hazards including earthquakes, landslides, floods, subsidence, radon, and asbestos; and, •participating in multidisciplinary teams.
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Who was first hydro engineering geologist...and what were his accomplishments.
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William Smith *"The map that changed the world" •Canal construction •Transport of coal *Published 1815 -1817
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What is the height and width of Natural Bridge?
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215 feet tall and 90 feet wide
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What makes natural bridge unique to other bridges>
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only known natural arch in the world to have a highway across it -U.S. Rt 11
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What is the thickness at of the bridge?
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55 feet
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What is the historical background of Natural Bridge?
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*Purchased by Thomas y Jefferson in 1774 from King George III *Held by heirs until 1833 *Present owner purchased it in 1984
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What date did a rock fall occur at Natural Bridge?
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Saturday Saturday October 23, 199
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What is the engineering definition of bedrock vs. soil
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Bedrock- Hard durable continuous rock mass lying at or near surface which must be excavated by systematic drilling and blasting. A.K.A "Rock Borrow" Soil-Loose unconsolidated (non-lithified) material lying above the bedrock, which can be excavated by conventional means. A.K.A "Common Borrow"
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What dose the distinction of soil effect when constructing?
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The Cost
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What is the Agricultural Definitions of Soil?
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A= Top soil, organic, black zone of mineral leaching. B= Zone of accumulation, red/brown clays. C= Saprolite, weathered bedrock
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The distinction between engineering "soil" and agricultural soil is NOT important when classifying them. (True/False)
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False
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Define Transported soil
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-unlithified materials that overlie bedrock from which they were not derived?
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Give an example of Transported Soils....
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Glacial, lacustrine, marine, eolian, alluvial (flood planes, terraces, deltas, fans) shoreline, gravity deposits, man-made fill, volcanic deposits and cumulose fill
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Define Residual Soils
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Unlithified minerals derived from the weathering of material it overlies
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Name 4 soil formations?
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1) Physical Weathering 2) Chemical Weathering 3) Hydrolysis 4 )Oxidation
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Define Physical Weathering
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Mechanically breaking rock apart into smaller pieces with out chemically altering the mineral composition
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Define Chemical Weathering
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Decomposition of rock by chemical reactions which alter the chemical composition of the rock forming new minerals.
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What is Hydrolysis?
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Weathering reaction from contact with water, probably assisted by naturally occurring carbonic acid, Produces clay minerals (montomorillinite, kalinite, illite)
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What is oxidation
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Cations from hydrolysis react with O2 to produce oxides usually red hematite.
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What are weather processes?
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Not all materials weather at the same rate. Rates of weathering can be compared on the Goldich Series ( same drawing as bowmen reaction series)
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Minerals that form early in the bowman's reaction series such as (Olivine) are most unstable and weather fastest at the earth's surfaces. (True/False)
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True
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What are the five factors that affect soil development and thickness?
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1) Climate 2) Time 3) Vegitation 4) Topography 5) Parent Material
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How dose one locate a soil/rock boundary?
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Drilling, Augering, & Coring
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Explain 3 problems that occur when boring a hole?
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1. Bedrock occurs at point where soil auger refuses to advance. 2. Bedrock occurs where split-spoon sampler will not advance with blows from standard sliding hammer. 3. Bedrock occurs where shelby tube sampler cannot be hydraulically pushed farther
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Bore holes are expensive too! (True/False)
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True
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What occurs during seismic refraction?
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1. Shock waves travel through different materials at different velocities. Soil is lessdense than rock so velocity will also be lessin soil. essso. 2. Waves will be bent (refracted) each time they encounter a boundary between layers with different velocities
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What are two kinds of weathered rock and the abbreviation for the names?
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(SWR)- Soft Weathered Rock (HR) - Hard Weathered Rock
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Define soft weathered rock...
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Material that can be penetrated with some difficulty using power augers and yields SPT values >100 blows but< SPT Refusal.
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Define hard weathered rock...
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Material that cannot be penetrated by power augers with great difficulty using power augers and yields SPT refusal
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What is SPT Refusal?
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When the soil has less than or equal to 1 inch of penetration per 50 blows.
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What dose an inferred rock line indicate?
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The the level at which augers could no longer penetrate.
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Hard Rock Symbols are not shown when rock is cored and only to that depth cored. (True/False)
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False
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What is core recovery (Rec.)?
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Total length of rock recovered in the core barrel divided by the total length of the core run times 100%
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What is rock quality Designation? (ROD)
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The total length of sound rock segment received that are longer that or equal to 4" divide by the total length of the core run times 100%.
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What happens during seismic refraction?
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1. Shock waves travel through different materials at different velocities. Soil is less dense than rock so velocity will also be less in soil. 2. Waves will be bent (refracted) each time they encounter a boundary between layers with different velocities.
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Ware are the three primary seismic waves and what do they do?
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P-waves: primary, compressional, fastest S-waves: secondary, shear L-waves: last, large, slowest and do most damage during earthquakes
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The P-wave velocities are used to calculate depth(D) to the soil/rock boundary and rippability ? (True/False)
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True
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What two values do you need from seismic refraction to determine bed rock?
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1) STP N-Value 2) Comprehensive wave velocity (fps)
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Resistivity is the resistance to the flow of ....
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an electrical current through a rock cylinder of length a and a cross-sectional area S. ρ = RS/a(for laboratory sample
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Resistivity and Conductivity are related to....
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Concentrations of electrolytes in the pore spaces -Type of soil or rock a. Porous sand & gravel have high resistivity when dry. Impermeable silt and clay have low resistivities. -Location of groundwater table
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Depths to Boundaries are found by....
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plotting cumulative resistivity graphs.
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Gravity is good for locating bodies
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of different density in the subsurface because gravitational force will change minutely over them.
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Give a high and low gravity example in the field.
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High gravity anomalies occur in dense igneous intrusions into low sedimentary rock. Low Gravity occurs in caverns and mines.
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How is Gravity measures?
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in gals X 10^-3 (in honor of Galileo) or miligals
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What is earths gravity?
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980 or 980,000 miligals
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Define Magnetism
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A magnetometer is used to measure the earth's magnetic field plus residual magnetism in subsurface material caused by the presence of magnetic minerals.
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The regional magnetic field is calculated and subtracted leaving only..........?
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The effects of residual magnetism.
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Variations in the residual magnetism indicate underground magnetic bodies in....?
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Mafic igneous intrusions Sand and gravel deposits that accumulate heavy minerals.
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How is magnetism measured?
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1 gamma = 10^-5 oersted
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What is 1 oersted is magnetic force equivalent to ?
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1 dyne acting in the direction of the magnetic vector (force causing acceleration if 1 cm/sec^2 on 1 Gm)
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Magnetic data provides information on
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~basement depth ~Unexpected relationships between the and a shallower exploration target. ~Can help define structures in detail
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How is magnetic data best used?
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In as synergistic manner.
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What other data sets is magnetic data integrated with when forming data sets?
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gravity, seismic, on surface and subsurface geologic information.
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When was the first magnetic map published?
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1977
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Please provide the soil classifications for the went worth scale.
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>2 mm....Gravel 2-1/16 mm....Sand 1/16-1/256 mm....Silt 1/256....Clay
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Please provide the soil classifications for the Phi Scale.
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-2 to -1.... Gravel -1 to+3.75.... Sand +3.75 to 8.0 Silt +8.0....Clay
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Please provide the soil classifications for the TBR Scale
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>2 mm....Gravel 2-.05 mm....Sand 0.05-0.005 mm....Silt <0.005....Clay
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What dose USDA stand for?
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U.S. Dept. of Agriculture
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What is the TBR ?
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Transportation Research Board
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Lit the three steps used to name the soil using one of the textural classifications:
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1. Remove gravel and larger sizes 2. Sieve the remainder, determine percent sand, clay, and silt. 3. Locate the name on appropriate ternary diagram
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What are the three ways a clay can be refereed too.
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1) Clay sometimes refers to the size of material. 2) Clay sometimes refers to particular group of phyllosilicate minerals (sheet like structure) 3) Clay sometimes refers to specific engineering properties or type of soil behavior.
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What is the difference between TBR and USDA clay sizes?
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TBR = <0.005 mm USDA = <0.002 mm
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In mineralogy clays are minerals which have?
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cohesion and plasticity when wet.
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What is the chemical make up of clays?
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They consist of sheets of hydroxyls (Al(OH)3, Mg(OH)2) altering with silicate sheets (Si2O5)
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What are the 3 types of clays?
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1) Two layer clay- Kaolinite and Halloysite 2)Three layer clay - smectite, illite, vermiculite 3) Mixed layer clay- chlorite
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Three layer clays have the tendency to...
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Swell
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Where is montomorillionite formed?
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Volcanic soils and ares of young sediments ex. costal planes of VA
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Soils that form on lithified sedimentary rock tend to be ....?
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Non-expansive
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Who first developed the unified soil classification system? And what was it used for?
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Originally developed by Arthur Casagrande for the army corps of engineers to use in air field construction.
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Soil classification can be checked in the field by conducting what test?
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Atterberg Limits Test
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How to determine if soil is Coarse or Fine?
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The soil is fine if >50% passes #200 sieve by weight (clay & silt) and the Coarse soil )
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What is the diamiter if the holes in a sieve #200
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0.74 .. diameter
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G=
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Gravel
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S=
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Sand
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M=
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Silt
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C=
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Clay
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o=
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Organics
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Pt=
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Peat
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W=
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Well graded (all sizes represented)
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P=
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Poorly Graded
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H=
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High Plasticity
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L=
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Low Plasticity
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GW=
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Well graded gravel
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GP=
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Poorly graded gravel
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SM=
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Silty Sand
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ML=
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Low Plasticity Silt
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CL=
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Low plasticity clay
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MH=
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high plasticity silt
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CH=
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High plasticity clay
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Explain clays, silts, and sands in reference to cohesion?
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Clays have cohesion Silt have little to no cohesion Sand has no cohesion
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Soils that form on ithified sedimentay rock tend to be ....?
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Non-expansive
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What are three steps when determining classification of soil?
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1) Examine the soil 2) Examine grain size 3) Size Distribution Diagram
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What is Effective Size D10
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The size for which 10% of soil is finer and can approximate soil permeability
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Are uniform soils more permeable than non- uniform soils?
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True
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What percentage must pass through a 200 # sieve to identify it as coarse. And what type of soil is it?
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50% or less---gravel or sand
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What percentage must pass through a 200 # sieve to identify it as fine. And what type of soil is it?
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Greater than 50% --- silt of clay
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What are the four consistencies that soil must pass through when drying?
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1) Liquid- flows 2) Plastic- can be deformed without cracking 3)Semi-Solid- cracks a little 4) Solid- brittle, breaks under pressure
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What is the Atterberg limits ?
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Are the water contents (w%) of the soil as it changes from one consistency to the next.
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Water content in percent is equivalent to ...
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(mass water /mass solids)*100
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What is the liquid limit device?
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The liquid limit device determines LL by jarring a moist sample and observing closure of a groove in the soil. (LL= water content when grove 13 mm wide closes in exactly 25 blows of the cup.)
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What dose LL stand for?
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Liquid Limit- The water content of the soil when just between a liquid and a plastic consistency.
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What dose PL stand for?
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Plastic Limit- The water content of the soil when just between plastic and solid in consistency.
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Who created the plasticity charts?
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Cassagrande
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Plasticity chart can help you find the
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liquid limit & plasticity chart
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What dose high PI/ Plasticity Index indicate?
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More compressieve soil
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What is the equation for plasticity index?
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LL-PL=PI
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Any soil sample can be thought of as containing _______ possible phases.
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Three possible phases
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What are the soil phase of a soil phase diagram?
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Air, Water, Solids
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What is the geological definition of Compaction?
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Reduction in volume that occurs under the load of overlying sediment as part of the sedimentary process. (Includes both engineering compaction and consolidation)
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What is the geological definition for consolidation ?
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Lithification, total process by which sediment becomes rock. (Includes geologic compaction and cementation)
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What is the goal of soil compaction?
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To decrease the void ratio and permeability.
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What is the engineering definition of compaction ?
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Reduction of volume by rearrangement of particles without the outflow of water involved or required.
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What is the definition of engineering consolidation?
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Reduction of volume caused by the outflow of water as load is transfered from the water to the soil particles. ( This process is time related and takes longer than compaction)
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At what depth are the layer of lift during compaction?
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(6-12inches)
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What three tools are the lift layers compacted by?
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Vibrating rollers (cohesion-less soils-sandy) Sheep's foot roller (cohesive soil - clayey) Hand held tampers.
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What is a controlled earth fill?
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A fill in which the materials are carefully controlled. Not allowing rocks bigger than a foot in diameter, excess water content, also no tree content or organic soils.
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What is the case history for Blacksburg High School?
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The school was built on half bed-rock and half fill dirt. Most-likely the fill dirt was not controlled and contained organic materials. There was significant foundation problems, including water damage through the cracks in the foundation. Officials were worried about water seeping into the electrical system.
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What is the case history of East-side H.S. in Rockingham County Virginia?
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The foundation was partially built on a Limestone deposit and the rest was constructed on fill dirt. The was post the Blacksburg high school issue and they wanted to avoid a total structural loss; and got the problem corrected.
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What is the case history for Radford?
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Radford is built on set of old river terrace deposits, projecting toward flood planes; in some area there is 30 feet of fill which was supposed to be controlled. Instead there were large trees, boulders, and washing machines thrown in for compaction. Some areas experienced sinking of parking lots ect.
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What are two methods of compaction testing?
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1) Proctor testing 2) Field Density Testing
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Define proctor testing?
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of samples in lab to determining the optimum unit weight and moisture content to get densest soil for a given compactive effort. (A measure of the energy put into the compaction)
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What is field density testing?
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is conducted during construction to ensure that the soils are properly compacted according to Proctor Test results.
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In the proctor test curve what happens if the soil is compacted too dry?
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The fill may be less flexible causing cracking and will result in piping (internal erosion of the fill)
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In the proctor test what happens if the soil is too wet?
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The fill may be to flexible and not as strong.
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What are the effect of water on Silty soils, and Clayey Soils?
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Silty - Usually dry out quickly and need to be kept wet with water trucks. Clayey - They are usually too wet in the field and need to be spread out and dried.
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What is the modified proctor test?
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Uses same size mold, compact in 5 lifts instead of 3, Uses a 10 lb. hammer, 25 blows per lift, and the hammer falls 18 inches instead of 12. The compactive effort is about 4.5X that of the standard effort.
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What are the benefits of a modified proctor test ?
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Denser fill greater strength Less Moisture
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What soils must be used to complete a proctor test?
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Cohesive Soils (clays and moist silts)
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What soils must be used in a relative density test?
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cohesionless soils (sands)
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What happens to cohesionless soils during earthquakes?
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Liquification of fine sand and silt with low relative density and high ground water table.
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What is liquification?
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the loss of bearing capacity of a soil caused by vibrations.
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What happens to the pore space when vibrations occur?
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Vibrations increase the pressure within water in the pore space. This decreases the pressure between individual grains .
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What is effective stress?
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A decrease in pressure between individual grains and controls soil strength.
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What are three methods of measuring Field Density and Moisture Content?
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1) Sand Cone 2) Speedy Moisture Meter 3)Nuclear Density Gages
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What is the Sand Cone device?
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A device for measuring the volume of a hole from which the soil has been remove by filling the hole with sand of a known density and determining the weight of the sand required to do so . From the volume of the hole and the weight of the soil removed can be found the soil density.
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What is stress?
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An internal condition within a substance caused by an external pressure. (force acting over a specified area)
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What are three types of Stress?
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Compressive, Tensile, Shear
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What is compressive stress
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Compression refers to a set of stresses directed toward the center of a rock mass. The compresive strength refers to the maximum stress applied before failure.
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What is tensile stress?
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A stress which stress rock in two opposite directions.
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What is shear stress ?
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A stress component parallel to a given surface such as a fault plan that results from forces applied parallel to the surface or from remote forces transmitted through the surrounding rock.
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What is strain?
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Deformation of a substance as a result of stress.
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What is strength?
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The Maximum stress that can be applied to a substance before it fails.
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What is failure?
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Excess strain in a substance that could cause a rupture or plastic deformation beyond allowable limits.
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What is total stress
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Stress in a soil resulting from the weight of overlying soil and water
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What is neutral stress
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Water pressure within a soil that acts to puch soil grains apart.
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What is effective stress?
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Stress withing the soil particals in the soil it equals total minus neutral stress.
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Effective stress controls?
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The strength of a soil.
