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Settlement of Foundations on Sand Schmertmann Method

Settlement of Foundations on Sand Schmertmann Method. M. Zoghi, Ph.D., P.E. Department of Civil & Environmental Engineering. CEE 434 Geotechnical Design 6 October 2008. Immediate Settlement of Shallow Foundations on Sand. Comparisons of Vertical strain from FEM. Schmertmann’s Method.

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Settlement of Foundations on Sand Schmertmann Method

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  1. Settlement of Foundations on SandSchmertmann Method M. Zoghi, Ph.D., P.E. Department of Civil & Environmental Engineering CEE 434 Geotechnical Design 6 October 2008

  2. Immediate Settlement of Shallow Foundations on Sand

  3. Comparisons of Vertical strain from FEM

  4. Schmertmann’s Method • Primarily used to estimate immediate settlement of foundations • in sand • Specially useful when SPT and/or CPT data are available • Results are compatible with field measurements • Based on analysis of vertical strain distribution with a linear • elastic half space subjected to a uniform pressure

  5. Schmertmann's Method Required Data A profile of standard penetration resistance N (blows/ft) versus depth, from the proposed foundation level to a depth of 2B, or to boundary of an incompressible layer, whichever occurs first. Soil Type Es/N Silts, sands silts, slightly cohesive silt-sand mixtures 4 Clean, fine to med, sands & slightly silty sands 7 Coarse sands & sands With little gravel 10 Sandy gravels and gravels 12 http://www.vulcanhammer.net/utc/ence361/f2001/361-sl10.pdf

  6. Schmertmann's Data • Required Data • Least width of foundation = B • Depth of embedment = Df • Proposed average contact pressure = q • Approximate unit weights of surcharge soils, and • position of water table if within Df • If the static cone bearing value qc, measured • compute Es, based on Es, = 2qc.

  7. Analysis Procedure • Divide the subsurface soil profile into a convenient number of layers of any thickness, each with constant N over the depth interval 0 to 2B below the foundation. • Prepare a table using the indicated column headings. Fill in columns 1, 2, and 3 with the layering assigned above. • List SPT (or CPT) quantities in column 4. • Estimate the influence values from the graph and list in column 5. • Calculate Es values and list in column 6 • Compute the incremental settlement, (Iv /Es)/z, and add up!

  8. Strain Influence Factors

  9. Cone Penetrometer Resistance

  10. Example Problem

  11. Case Study Kansai International Airport (KIA) Source: Rajul Teredesai

  12. Key Features • Located on a biggest man-made island in Osaka Bay, Japan • Constructed cost over $14 billion • The island of 4 X 1 km, constructed in around 18m of water, entirely from landfill • Project Started in 1986 • Opened for flights in 1996 • The ASCE named KIA the #2 civil engineering project of the 20th century, second only to the Panama Canal

  13. Kansai Airport Aerial View

  14. Seawall After Completion Seawall Construction

  15. Mechanism of Sand Drains

  16. The weight of the piled sand forces the water in the clay to move outward along the sand piles. Advantage of Sand Drains

  17. Architect: Renzo Piano KIA Terminal Building

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