Download ENGINEERING GEOLOGY EXAM SOLUTION and more Exams Geology in PDF only on Docsity!
ENGINEERING GEOLOGY EXAM
SOLUTION
Define Engineering Geology - Answer -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. Define Geological Engineering - Answer -The engineering discipline specializing in the evaluation and design of engineering projects, in or on the earth and the evaluation of earth materials. What are Geological engineers work typically involves - Answer - Mining Petroleum recovery Civil engineering And deal with design and performance of the project Compare a engineering geologist and geological engineer. - Answer -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.
- Answer -The application of geologic data collection techniques and principles to the study of rock and soil material , and ground water, so that geologic factors affecting the design, construction, operation, and maintenance of engineering structures and the development of ground-water resources available for us to use in engineering practices. The scope of work includes the many
phases of engineering in which man works with rock, soil, and water. Engineering Geology includes - Answer -•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. Who was first hydro engineering geologist...and what were his accomplishments. - Answer -William Smith *"The map that changed the world" •Canal construction •Transport of coal *Published 1815 - What is the height and width of Natural Bridge? - Answer - feet tall and 90 feet wide What makes natural bridge unique to other bridges> - Answer - only known natural arch in the world to have a highway across it - U.S. Rt 11 What is the thickness at of the bridge? - Answer -55 feet What is the historical background of Natural Bridge? - Answer - *Purchased by Thomas y Jefferson in 1774 from King George III *Held by heirs until 1833 *Present owner purchased it in 1984
Name 4 soil formations? - Answer -1) Physical Weathering
- Chemical Weathering
- Hydrolysis 4 )Oxidation Define Physical Weathering - Answer -Mechanically breaking rock apart into smaller pieces with out chemically altering the mineral composition Define Chemical Weathering - Answer -Decomposition of rock by chemical reactions which alter the chemical composition of the rock forming new minerals. What is Hydrolysis? - Answer -Weathering reaction from contact with water, probably assisted by naturally occurring carbonic acid, Produces clay minerals (montomorillinite, kalinite, illite) What is oxidation - Answer -Cations from hydrolysis react with O to produce oxides usually red hematite. What are weather processes? - Answer -Not all materials weather at the same rate. Rates of weathering can be compared on the Goldich Series ( same drawing as bowmen reaction series) 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) - Answer -True What are the five factors that affect soil development and thickness? - Answer -1) Climate
- Time
- Vegitation
- Topography
- Parent Material How dose one locate a soil/rock boundary? - Answer -Drilling, Augering, & Coring Explain 3 problems that occur when boring a hole? - Answer -1. Bedrock occurs at point where soil auger refuses to advance.
- Bedrock occurs where split-spoon sampler will not advance with blows from standard sliding hammer.
- Bedrock occurs where shelby tube sampler cannot be hydraulically pushed farther Bore holes are expensive too! (True/False) - Answer -True What occurs during seismic refraction? - Answer -1. Shock waves travel through different materials at different velocities. Soil is lessdense than rock so velocity will also be lessin soil. essso.
- Waves will be bent (refracted) each time they encounter a boundary between layers with different velocities What are two kinds of weathered rock and the abbreviation for the names? - Answer -(SWR)- Soft Weathered Rock (HR) - Hard Weathered Rock Define soft weathered rock... - Answer -Material that can be penetrated with some difficulty using power augers and yields SPT values >100 blows but< SPT Refusal. Define hard weathered rock... - Answer -Material that cannot be penetrated by power augers with great difficulty using power augers and yields SPT refusal
What two values do you need from seismic refraction to determine bed rock? - Answer -1) STP N-Value
- Comprehensive wave velocity (fps) Resistivity is the resistance to the flow of .... - Answer -an electrical current through a rock cylinder of length a and a cross- sectional area S. ρ = RS/a(for laboratory sample Resistivity and Conductivity are related to.... - Answer - 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 Depths to Boundaries are found by.... - Answer -plotting cumulative resistivity graphs. Gravity is good for locating bodies - Answer -of different density in the subsurface because gravitational force will change minutely over them. Give a high and low gravity example in the field. - Answer -High gravity anomalies occur in dense igneous intrusions into low sedimentary rock. Low Gravity occurs in caverns and mines. How is Gravity measures? - Answer -in gals X 10^-3 (in honor of Galileo) or miligals What is earths gravity? - Answer -980 or 980,000 miligals
Define Magnetism - Answer -A magnetometer is used to measure the earth's magnetic field plus residual magnetism in subsurface material caused by the presence of magnetic minerals. The regional magnetic field is calculated and subtracted leaving only..........? - Answer -The effects of residual magnetism. Variations in the residual magnetism indicate underground magnetic bodies in....? - Answer -Mafic igneous intrusions Sand and gravel deposits that accumulate heavy minerals. How is magnetism measured? - Answer -1 gamma = 10^- oersted What is 1 oersted is magnetic force equivalent to? - Answer - dyne acting in the direction of the magnetic vector (force causing acceleration if 1 cm/sec^2 on 1 Gm) Magnetic data provides information on - Answer -~basement depth ~Unexpected relationships between the and a shallower exploration target. ~Can help define structures in detail How is magnetic data best used? - Answer -In as synergistic manner. What other data sets is magnetic data integrated with when forming data sets? - Answer -gravity, seismic, on surface and subsurface geologic information. When was the first magnetic map published? - Answer -
What is the difference between TBR and USDA clay sizes? - Answer -TBR = <0.005 mm USDA = <0.002 mm In mineralogy clays are minerals which have? - Answer -cohesion and plasticity when wet. What is the chemical make up of clays? - Answer -They consist of sheets of hydroxyls (Al(OH)3, Mg(OH)2) altering with silicate sheets (Si2O5) What are the 3 types of clays? - Answer -1) Two layer clay- Kaolinite and Halloysite 2)Three layer clay - smectite, illite, vermiculite
- Mixed layer clay- chlorite Three layer clays have the tendency to... - Answer -Swell Where is montomorillionite formed? - Answer -Volcanic soils and ares of young sediments ex. costal planes of VA Soils that form on lithified sedimentary rock tend to be ....? - Answer -Non-expansive Who first developed the unified soil classification system? And what was it used for? - Answer -Originally developed by Arthur Casagrande for the army corps of engineers to use in air field construction. Soil classification can be checked in the field by conducting what test? - Answer -Atterberg Limits Test
How to determine if soil is Coarse or Fine? - Answer -The soil is fine if >50% passes #200 sieve by weight (clay & silt) and the Coarse soil <50% passes#200 sieve by weight (sand & >) What is the diamiter if the holes in a sieve #200 - Answer -0. .. diameter G= - Answer -Gravel S= - Answer -Sand M= - Answer -Silt C= - Answer -Clay o= - Answer -Organics Pt= - Answer -Peat W= - Answer -Well graded (all sizes represented) P= - Answer -Poorly Graded H= - Answer -High Plasticity L= - Answer -Low Plasticity GW= - Answer -Well graded gravel GP= - Answer -Poorly graded gravel SM= - Answer -Silty Sand
What percentage must pass through a 200 # sieve to identify it as fine. And what type of soil is it? - Answer -Greater than 50% --- silt of clay What are the four consistencies that soil must pass through when drying? - Answer -1) Liquid- flows
- Plastic- can be deformed without cracking 3)Semi-Solid- cracks a little
- Solid- brittle, breaks under pressure What is the Atterberg limits? - Answer -Are the water contents (w %) of the soil as it changes from one consistency to the next. Water content in percent is equivalent to ... - Answer -(mass water /mass solids)* What is the liquid limit device? - Answer -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.) What dose LL stand for? - Answer -Liquid Limit- The water content of the soil when just between a liquid and a plastic consistency. What dose PL stand for? - Answer -Plastic Limit- The water content of the soil when just between plastic and solid in consistency. Who created the plasticity charts? - Answer -Cassagrande Plasticity chart can help you find the - Answer -liquid limit & plasticity chart
What dose high PI/ Plasticity Index indicate? - Answer -More compressieve soil What is the equation for plasticity index? - Answer -LL-PL=PI Any soil sample can be thought of as containing _______ possible phases. - Answer -Three possible phases What are the soil phase of a soil phase diagram? - Answer -Air, Water, Solids What is the geological definition of Compaction? - Answer - Reduction in volume that occurs under the load of overlying sediment as part of the sedimentary process. (Includes both engineering compaction and consolidation) What is the geological definition for consolidation? - Answer - Lithification, total process by which sediment becomes rock. (Includes geologic compaction and cementation) What is the goal of soil compaction? - Answer -To decrease the void ratio and permeability. What is the engineering definition of compaction? - Answer - Reduction of volume by rearrangement of particles without the outflow of water involved or required. What is the definition of engineering consolidation? - Answer - 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)
What are two methods of compaction testing? - Answer -1) Proctor testing
- Field Density Testing Define proctor testing? - Answer -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) What is field density testing? - Answer -is conducted during construction to ensure that the soils are properly compacted according to Proctor Test results. In the proctor test curve what happens if the soil is compacted too dry? - Answer -The fill may be less flexible causing cracking and will result in piping (internal erosion of the fill) In the proctor test what happens if the soil is too wet? - Answer - The fill may be to flexible and not as strong. What are the effect of water on Silty soils, and Clayey Soils? - Answer -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. What is the modified proctor test? - Answer -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. What are the benefits of a modified proctor test? - Answer - Denser fill
greater strength Less Moisture What soils must be used to complete a proctor test? - Answer - Cohesive Soils (clays and moist silts) What soils must be used in a relative density test? - Answer - cohesionless soils (sands) What happens to cohesionless soils during earthquakes? - Answer -Liquification of fine sand and silt with low relative density and high ground water table. What is liquification? - Answer -the loss of bearing capacity of a soil caused by vibrations. What happens to the pore space when vibrations occur? - Answer -Vibrations increase the pressure within water in the pore space. This decreases the pressure between individual grains. What is effective stress? - Answer -A decrease in pressure between individual grains and controls soil strength. What are three methods of measuring Field Density and Moisture Content? - Answer -1) Sand Cone
- Speedy Moisture Meter 3)Nuclear Density Gages What is the Sand Cone device? - Answer -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.
What is neutral stress - Answer -Water pressure within a soil that acts to puch soil grains apart. What is effective stress? - Answer -Stress withing the soil particals in the soil it equals total minus neutral stress. Effective stress controls? - Answer -The strength of a soil.
