1 / 33

SIGNIFICANT SOIL PROPERTIES

SIGNIFICANT SOIL PROPERTIES. M. Zoghi, Ph.D., P.E. Geotechnical Design Fall 2007. OUTLINE. Overview Permeability & Seepage Compressibility & Settlement Shear Strength Examples. II. Permeability and Seepage. Bernoulli’s Theorem Darcy’s Law Coefficient of Permeability

gannon
Download Presentation

SIGNIFICANT SOIL PROPERTIES

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. SIGNIFICANT SOIL PROPERTIES M. Zoghi, Ph.D., P.E. Geotechnical Design Fall 2007

  2. OUTLINE Overview Permeability & Seepage Compressibility & Settlement Shear Strength Examples

  3. II. Permeability and Seepage • Bernoulli’s Theorem • Darcy’s Law • Coefficient of Permeability • Flow Net Construction • Seepage Quantity • Uplift Pressure

  4. Bernoulli’s Theorem Total Head, h = Pressure Head (u/w) + Elevation Head (Z) + 0 Hydraulic gradient, i = h / L Das, 2001

  5. Darcy’s Law V = k i Das, 2001

  6. Coefficient of Permeability • Units: • Ft/min., ft/day, cm/sec, etc. • Factors: • Grain-size dist., void ratio, fluid viscosity, etc. • Typical Values • Empirical Relationships: • Hazen’s Formula: K(cm/sec) = C (0.8 to 1.2) D10 Typical Values Soil Type k (cm/sec) Clean Gravel 100-1 Coarse Sand 1.0-0.01 Fine Sand 0.01-0.001 Silty Clay 0.001-0.00001 Clay0.000001 2 D10 = Effective Size

  7. Lab Tests K = Q L / (Aht) Constant Head Test Das, 2001

  8. Falling Head Test K = 2.303 (aL/At) log (h1/h2)

  9. Draw-Down Field Tests 2 2 K = [2.303 q log (r1/r2)] / [ (h1 – h2) Das, 2001

  10. Elements of Flow Net Theory General • A set of flow lines and equip. lines • A flow line – along which a water particle travels • An equip. line – joining pts with the same piezometric elevations (I.e., hydraulic head) Step-by-Step (Trial Sketching) • Draw the hydraulic structure to a convenient scale • Establish the boundary flow & equip. lines • No more than 3 – 5 flow channels • Examine the flow net for being both perpendicular & pseudosquare

  11. McCarthy, 2002

  12. McCarthy, 2002

  13. Example U = (Total Head – Elev. Head)w McCarthy, 2002

  14. Stress Distribution Within Soil Mass Circular Area Boussinesq Theory

  15. III. Compressibility & Settlement • Fundamental Concepts • One-Dimensional Consolidation Theory • Load-Deformation Characteristics • Consolidation Characteristics • Stress Distribution • Amount of Consolidation • Time-Rate of Consolidation Said Big Ben to Leaning Tower of Pisa: " If you have the inclination, I have the time ..."

  16. Soil Profile Spring Analogy Lamb & Whitman, 1969 Das, 2001

  17. Laboratory Test Das, 2001

  18. Components of Settlement S = Sc + Ss + Sd S = Total Settlement Sc = Primary Consolidation Settlement Ss = Secondary Consolidation Settlement Sd = Distortion (immediate) settlement Das, 2001

  19. Typical e-log p curve Virgin Curve Rebound Curve Unloading Curve Recompression Curve Das, 2001

  20. Casagrande’s Method of Finding Preconsolidation Stress Cc Cc = 0.009(LL – 10)

  21. Components of Consolidation Settlement Normally Consolidated Soils: Sc = [Cc/(1+e0)] H log [(’0 + )/ ’0] Overconsolidated Soils:(OCR = ’c /’0) Sc = [Cs /(1+e0)]H log [(’0 + )/ ’0]for (’0 + ) ’c Sc = [Cs /(1+e0)]H log (’c /’0) + [Cc/(1+e0)] H log [(’0 + )/ ’c] for (’0 + ) ’c Secondary Consolidation: Ss = [C/(1+ep)]H log (t1/t2) Cs = 1/5 to 1/10 of Cc

  22. Time-Rate of Consolidation Cv = Tv H2dr / t Das, 2001

  23. Das, 2001

  24. Settlement-Time Curves

  25. IV. Shear Strength Coduto, 1999

  26. Block Analogy • Attributed to three basic components: • Frictional resistance to sliding between solid particles • Cohesion and adhesion between soil particles • Interlocking and bridging of solid particles to resist deformation Coduto, 1999

  27. Mohr-Coulomb Failure Criterion  = c + ’ tan  Das, 2001

  28. 1= 3tan2 (45 + /2) + 2c tan (45 + /2) Das, 2001

  29. Coduto, 1999

  30. Direct Shear Test Das, 2001

  31. Triaxial Compression Test Das, 2001

  32. Unconfined Compression Test Das, 2001

  33. V. Examples

More Related