Geology 229Engineering Geology

Lecture 1

The Syllabus and Introduction(West, Chs. 1, 20)

Engineering Geology close to life:Some recent nightmare memories

Great Hurricanes in New Orleans, 2005Gigantic boulder falls in January 2005Great Tsunami on Christmas Day 2004

Satellite image of Banda Aceh Shore, Indonesia, before the tsunami (June 23, 2004)

Satellite image of Banda Aceh Shore, Indonesia, after the tsunami (December 28, 2004)

January 10, 2005: A 25-foot boulder blocks Topanga Canyon Blvd. near Malibu, southern California, after a massive mudslide killed 3 and had up to 21 missing (AP).

What is Engineering Geology?

Engineering geology is the application of geological data, techniques and principles to the study of rock and soil surficial materials, and ground water. This is essential for the proper location, planning, design, construction, operation and maintenance of engineering structures. Engineering geology complements environmental geology, or hydrogeology.

What does Engineering Geology study?

Rock, soil, water, the interaction among these three constituents, as well as with engineering materials and structures.

Why Engineering Geology matter?

• Serve civil engineering to provide information in 3 most important areas:– Resources for construction;

• Aggregates, fills and borrows.– Finding stable foundations;

• Present is the key to the past –geology• Past is the key to the future -engineering

– Mitigation of geological hazards • Identify problems, evaluate the costs, provide

information to mitigate the problem

The Engineering Geology was established in US after the St. Francis Dam near Los Angeles, CA failed on March 12, 1928. Engineering community realized the importance of Geology factor in civil engineering.

After failure with the ‘Tombstone’ in the center

Before failure

Main reasons for dam failure:1, Sedimentary rocks on the west lost strength when it is wet;2, The fault separating the west and east rock formations started to leak water;3, Schist on the east increases pore pressure and lost shear strength after wet.

General Outline of Engineering Geology

1, Rock description and identification;2, Engineering properties of rocks (e.g., foundation), material for construction (e.g., aggregates);3, Rock weathering and soil development;4, Map reading, both topographic and geologic;5, Structure aspects – bedding, joints, and faults;6, Mass movement and landslides;7, Running water-erosion, flood effects, water impoundment;8, Groundwater control during construction, water supply, pollution, subsidence, slope instability;9, Shoreline erosion and protection;10, Earthquakes and earthquake engineering;11, Glacial deposits;12, Arid environments;13, Subsurface geology, condition of stress at depth (for excavation, tunneling etc.)

Highway Engineering Geology Considerations

1, Highway alignment, locations of right-of-way for the proposed construction;2, Subsurface exploration along highway centerline and bridge foundations;3, Classification of materials for excavation, rock versus common borrow (soil);4, Cut and fill volumes determined to minimize the need of offsite borrow pits or rock waste areas; volume changes in both soil and rock from the cut to the fill are estimated;5, Recommend angle of back slope (rock cut slope) based on rock conditions;6, Groundwater aspects related to construction;7, Evaluation of landslide-prone areas;8, Recognition of compressible soil materials;9, Construction materials, location and inventory;10, highway effects on adjacent landowners;

General Outline of Environmental Geology

1, Geological constraints to constructionsiting sanitary landfills;septic tank percolation fields;groundwater pollutions;

2, Environmental health chronic diseases related to geologic environment;trace elements and health;

3, Human interaction with the environmenteffects of urbanization on landscape;water supply and disposal;

4, Mineral resources and depletionmineral resource and population;environmental impact and mineral development;resources vs reserves;

5, Land use and land use planningEnvironmental impact of urban development;

A Comparison between Engineering Geology and Environmental Geology

Engineering Geology

• Established in 1928 after the failure of the St. Francis Dam;

• More physical geology oriented;

• More quantitative;• Focused on engineering

construction.

Environmental Geology

• Established in later 1960s;

• Physical and biological geology;

• Less quantitative(?);• Broader area including

hazards, health, mineral depletion, land use and land use planning, etc.

In the area covered by the permafrost, the surface vegetation is dominated by black spruces that are relatively short due to their shallow root systems constrained by the hard ice. In the area where the permafrost is gone, one can find tall trees like birches.

Cross Alaska Pipeline

Engineering geologists contribute to the design of structures such as the Alaskan pipeline near Fairbanks and many other edifices. The pipeline was built in the 1970s to transport crude oil from the Alaskan North Slope to the port of Valdez in southern Alaska. Ground conditions near the surface (permafrost and other processes) and those at depth (substrate conditions, potential seismic activity, position of faults etc.) must be clearly understood and taken into consideration to guarantee the integrity of engineered structures. The photograph shows the raised pipeline (to prevent warm oil from melting the permafrost) and the staggered shape of the pipeline (to allow elasticity during earthquake shocks).

Railway in Tibetan Plateau – “the roof of the world”

Louis Agassiz’ Statue after 1906 San Francisco Earthquake

Louis Agassiz

The old Wishell Seismograph for recording strong earthquake motions

Earthquake Engineering

Studies of the effects of earthquakes on people and their environment, with methods of reducing these effects.

Earthquake Engineering involves:

geology, seismology, geotechnical engineering, structural engineering, risk analysis with also

social, economic, and political factors

SI Unit System

• SI – Le Systeme International d’Unites• Base units• Derived units

SI base units The SI is founded on seven SI base units for seven base quantities assumed to be mutually independent, as given in Table 1.

Table 1. SI base units

Base quantityName Symbol

length meter mmass kilogram kgtime second sElectric current ampere Athermodynamic temperature

Kelvin K

amount of substance mole molluminous intensity candela cd

SI derived units

Other quantities, called derived quantities, are defined in terms of the seven base quantities via a system of quantity equations. The SI derived units for these derived quantities are obtained from these equations and the seven SI base units. Examples of such SI derived units are given in Table 2, where it should be noted that the symbol 1 for quantities of dimension 1 such as mass fraction is generally omitted.

Table 2. Examples of SI derived units

Derived quantityName Symbol

Area Square meter m2

Volume Cubic meter m3

Speed, velocity meter per second m/sAcceleration meter per second

squaredm/ s2

Density kilogram per cubic meter kg/m3

Specific volume cubic meter per kilogram m3/kgAmount-of-substance concentration

mole per cubic meter mol/m3

Luminance candela per square meter cd/m2

Frequency Revolution per second 1/secAngular frequency Radian per sec Radian/secWave number Radian per meter Radian/mWave length meter m