PHYSICAL SCIENCE FINAL Liquefaction Doreen Wallace, Tesla Grogan, Amber Ward, Erik Garcia, Cinthia Salas, Alexis Albers
Liquefaction What is it? Conditions needed How it works Effects of Liquefaction Soil liquefaction Sinkholes Bedrock Earthquakes CONTENT
LIQUEFACTION What is it? Loose sand and silt that is saturated with water can behave like a liquid when shaken by an earthquake How does it work? The soil can loose its ability to support structures, flow down even very gentle slopes, and erupt to the ground surface to form sand boils. Many of these phenomena are accompanied by settlement of the ground surface usually in uneven patterns that damage buildings, roads and pipelines Earthquake waves cause water pressures to increase in the sediment and the sand grains to lose contact with each other, leading the sediment to lose strength and behave like a liquid.
3 CONDITIONS NEEDED These three conditions are needed for liquefaction to occur: loose, granular sediment typically "made" land and beach and stream deposits that are young enough (late Holocene) to be loose. saturation of the sediment by ground water water fills the spaces between sand and silt grains strong shaking all parts of the San Francisco Bay region have the potential to be shaken hard enough for susceptible sediment to liquefy.
EFFECTS OF LIQUEFACTION Loss of bearing strength the ground can liquefy and lose its ability to support structures. Tilted apartment buildings, 1964, Niigata, Japan earthquake Tilted home in Mission District, 1906 San Francisco earthquake
EFFECTS OF LIQUEFACTION lateral spreading - the ground can slide down very gentle slopes or toward stream banks riding on a buried liquefied layer. Burning gas main ruptured by lateral movement, Balboa Blvd in Granaa Hills, 1994 Northridge earthquake Road damaged by lateral spread, near Pajaro River, 1989 Loma Prieta earthquake.
EFFECTS OF LIQUEFACTION sand boils - sand-laden water can be ejected from a buried liquefied layer and erupt at the surface to form sand volcanoes; the surrounding ground often fractures and settles. Sand boils in Milpitas mud flat, 1906 San Francisco earthquake Sand boils along a fissure near the Pajaro River, 1989 Loma Prieta earthquake
EFFECTS OF LIQUEFACTION flow failures earth moves down steep slope with large displacement and much internal disruption of material. Flow failure in highway fill, Lake Merced, 1957 Daly City earthquake
EFFECTS OF LIQUEFACTION ground oscillation the surface layer, riding on a buried liquefied layer, is thrown back and forth by the shaking and can be severely deformed. Walkway and pavement buckled by ground oscillation, Marina District of San Francisco, 1989 Loma Prieta earthquake
EFFECTS OF LIQUEFACTION flotation light structures that are buried in the ground (like pipelines, sewers and nearly empty fuel tanks) can float to the surface when they are surrounded by liquefied soil. settlement when liquefied ground re-consolidates following an earthquake, the ground surface may settle or subside as shaking decreases and the underlying liquefied soil becomes more dense. Settlement and disruption of ground and pavement over filled ground, Dore Street, 1906 San Francisco earthquake
SOIL LIQUEFACTION Poorly drained fine soils are more susceptible to liquefaction (sandy, silty, gravelly) Occurs when water-saturated unconsolidated soils affected by seismic waves that cause vibrations during earthquakes
SOIL When earthquake shock occurs in waterlogged soils, the pore spaces collapse and that causes a decrease in the volume of the soil. This process increases the water pressure between soil grains and it causes grains to move freely in the watery matrix. This lowers the soil s resistance of shear stress and this can cause soil to take on characteristics of a liquid. The soil then deforms and structures can be damaged because of a loss of support. Buildings that are constructed on loose soils can tilt easily when liquefaction occurs because the soil does not support the foundations of the structures. Structures on soil or bedrock are likely to suffer less damage when it comes to an earthquake.
SOIL LIQUEFACTION https://www.youtube.com/watch?v=yzjebz GLUEg https://www.youtube.com/watch?v=536xsz_ XkSs
SOIL LIQUEFACTION
SINKHOLES Sinkholes are pits in the ground that form in areas where water gathers without external drainage They are common where the rock below the surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved in groundwater circulating them. Collapses can be small or big-vary in area and depth In the U.S sinkholes are especially common in Texas, Alabama, and Missouri, Kentucky, Tennessee, Pennsylvania, and Florida.
When and where do they happen? Most of the time, sinkholes form gradually Though sometimes the collapse is sudden-sinkholes will open up and swallow cars, homes and street In the U.S sinkholes are especially common in Texas, Alabama, and Missouri, Kentucky, Tennessee, Pennsylvania, and Florida SINKHOLES
SINKHOLES
BEDROCK Bedrock, a deposit of solid rock that is typically buried beneath soil and other broken or unconsolidated material. Bedrock is made up of igneous, sedimentary, or metamorphic rock It often serves as the parent material (the source of rock and mineral fragments) for regolith and soil. Bedrock is also a source of nitrogen. A bedrock deposit that occurs at Earth s surface is called an outcrop.
BEDROCK Here is an example of a picture of some exposed bedrock near Sanikiluaq, Flaherty, Belcher islands in Canada. Bedrock is affected by the process of weathering and erosion. The weathering of bedrock also frees large amounts of nitrogen that can be taken up by plants and other forms of life.
EARTHQUAKE Any Sudden shaking of the ground caused by the passage of seismic waves through the Earth s rocks. Seismic waves are produced when some form of energy stored in Earth s crust is suddenly released. usually when masses of rock straining against one another suddenly fracture and slip. Little was understood about earthquakes until the emergence of seismology Seismology, involves the scientific study of all aspects of earthquakes, has yielded answers to such long-standing questions as to why they occur.
SKILLS DEVELOPED Research Source utilization PowerPoint Presentation creation and editing Public speaking How to speak concisely with inflection Collaboration/Communication Google Drive
DEMONSTRATION Instructions materials list for demonstration Video Video of demonstration of Liquifaction
BEFORE AND AFTER
SOURCES https://www.livescience.com/44123-what-are-sinkholes.html https://www.britannica.com/science/sinkhole https://www.britannica.com/science/soil-liquefaction https://geomaps.wr.usgs.gov/sfgeo/liquefaction/aboutliq.html https://www.britannica.com/science/bedrock