soil mechanics

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Principles of Effective stress, capillarity
and seepage through soil
Dr. Amit Srivastava, PhD, M.ASCE, LMIGS, LMISRMTT, MITS,
MISSMGE, AMIE
[B.E. University of Roorkee (now IIT Roorkee),
M.E. & Ph.D, IISc, Bangalore]
Assistant Professor (Senior Grade), Department of Civil Engineering
Jaypee University of Engineering & Technology,
Agra-Bombay Road, Raghogarh, District: Guna
Madhya Pradesh - 473 226, India
Mob.No. (+91)94797729, Home: 07544267030

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Effective stress for saturated soils

3. Effective stress for saturated soils
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4. Effective stress for saturated soils
Total Stresses
It is the stress acting at a point in a soil mass with a
horizontal top surface. The total stress is computed
as the total weight of a column of unit area above
the point.

5. Total Stresses
The pore or neutral stress (uw) is the stress within the
water voids. Since this stress is hydrostatic, it acts
equally in all directions. Under no flow conditions
(static),
Effective stress for saturated soils

6. Effective stress for unsaturated soils
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7. Effective stress for unsaturated soils
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8. Example
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9. Example
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10. Capillarity in soils
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11. Water movement by capillary action
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12. Capillarity in soils
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13. Capillarity in soils
Approximate relationship suggested by Terzaghi
and Peck (1967) is of the form
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Where. e is the void ratio, D10 is the effective grain size in cm
and C is an empirical constant which have a value in the
range of 0.1 – 0.5 cm2
It is important to note that two different soil mass with the same
D10 can have different pore size distribution depending on soil
structure, fabric, geological history etc., leading to variable
capillary rise.

14. Example
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15. Example
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16. Permeability of soil
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17. Permeability of soil
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18. Permeability of soil
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19. Permeability of soil
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20. Permeability of soil
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21. Permeability of soil
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22. Permeability of soil
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23. Permeability of soil
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24. Permeability of soil
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25. Permeability of soil
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26. Permeability of soil
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27. Permeability of soil
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28. Permeability of soil
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30. One Dimensional Seepage –
stresses due to flow
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31. Seepage through soils –
2D seepage
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32. Seepage through soils
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33. Seepage through soils
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34. Seepage through soils
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35. Seepage through soils
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Flownet -Drawing Method:
1. Draw to a convenient scale the cross
sections of the structure, water elevations,
and aquifer profiles.
2. Establish boundary conditions and draw one
or two flow lines Ψ and equipotential lines Φ
near the boundaries.

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Method:
3. Sketch intermediate flow lines and equipotential
lines by smooth curves adhering to right-angle
intersections and square grids. Where flow
direction is a straight line, flow lines are an equal
distance apart and parallel.
4. Continue sketching until a problem develops. Each
problem will indicate changes to be made in the
entire net. Successive trials will result in a
reasonably consistent flow net.

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Method:
5. In most cases, 5 to 10 flow lines are usually
sufficient. Depending on the number of flow
lines selected, the number of equipotential
lines will automatically be fixed by geometry
and grid layout.
6. Equivalent to solving the governing
equations of GW flow in 2-dimensions.

39. Seepage through soils
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40. Seepage through soils
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41. Flow net – unconfined flow
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42. Flow net – unconfined flow
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43. Flow net – unconfined flow
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44. Flow net – unconfined flow
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45. Flow net – unconfined flow
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46. Examples
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58. Seepage in Anisotropic soil conditions
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59. Seepage in Anisotropic soil
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60. Seepage in Anisotropic soil
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61. Seepage in Anisotropic soil
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62. Seepage in Anisotropic soil
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63. Flow through Non-Homogeneous soil
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64. 68
Piping in Granular Soils

65. Thank you
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