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bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
bearing capacity of multi edge foundations
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bearing capacity of multi edge foundations

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a numerical investigation on bearing capacity of multi edge foundations using FLAC 3D software.

a numerical investigation on bearing capacity of multi edge foundations using FLAC 3D software.

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  • 1. K.N.T. University of Technology<br />Faculty of Civil Engineering<br />Numerical Analysis of Load-Settlement Behavior of Multi Edge foundations<br />Supervisor:<br />Dr. Mahmoud Ghazavi<br />By:<br />Soroush Mokhtari<br />March 2007<br />
  • 2. 1st Season :<br />Introduction<br />Geosynthetics<br />Improving soil <br />bearing capacity<br />Soil Reinforcment<br /> ....<br />Improving Bearing capacity<br />...<br />Skirted foundations<br />Improving <br />geometry of foundation<br />Shell foundations<br />Multi edge foundations<br />Controlling the Numerical model <br />Usage of experimental result in Numerical methods<br />What are the effective parameters ?<br />
  • 3. 2nd Season:<br />Pervious Studies<br />Ghazavi & Hadiani (2004)<br />Bearing capacity of cross shape foundations are more than square foundations when they have the same width<br />Bearing capacity of cross shape foundation is more than the others<br />The bearing capacity of these foundations can be estimated by the following equations.<br />
  • 4. 2nd Season:<br />Pervious Studies<br />Stuart’s theory (1962):<br />
  • 5. 3ed season:<br />Modeling (FLAC 3D) & Controlling the model<br />Size of the model<br />Which parameters can affect the results ?<br />Fragment of elements in <br />Regions with High stress gradient<br />Controlling Numerical model<br />Propriety of neighbor elements<br />Magnitude of load increments<br />
  • 6. 3ed season:<br />The effect of size and location of the supports<br />There is an appropriate size which will neither affect the results nor waste time <br />Small model Absorption of plastic deformation <br />effects<br />Large model Waste of time and computer memory<br />Footing properties:<br />6 cm width Square<br />Soil properties:<br />E = 27 MPa<br />υ = .35<br />C ~ 0 kPa<br />Φ = 38.1 deg<br />
  • 7. 3ed season:<br />Size and Propriety of elements<br />Large elements less accurate results<br />effects<br />Very small elements waste of time and computer memory<br />
  • 8. 3ed season:<br />Magnitude of load increments<br />Large increments increase loading shocks <br />effects<br />Very small increment waste of time<br />Footing properties:<br />6 cm width square<br />Soil properties:<br />E = 27 MPa<br />υ = .35<br />C ~ 0 kPa<br />Φ = 38.1 deg<br />
  • 9. 3ed season:<br />The effects of soil parameters<br />Estimating unknown parameters<br />How can soil parameters affect the load-settlement behavior of the model<br />Controlling the model<br />Load-settlement behavior<br />Post failure behavior <br />Strength parameters<br />Elastic parameters<br />Module of elasticity<br />Internal friction angle<br />Dilatation angle<br />Poassio’s ratio <br />cohesion<br />
  • 10. 3ed season:<br />Effect of module of elasticity & poassio’s ratio<br />Footing properties:<br />6 cm width square<br />Soil properties:<br />C ~ 0 kPa<br />Φ = 38.1 deg<br /> E = 10 MPaυ = .2<br /> E= 20 MPaυ = .3<br /> E= 50 MPaυ = .35<br />In sand E varies from 5 to 85 Mpa and υ form 0.3 to 0.4<br />
  • 11. 3ed season:<br />Effect of dilatation angle<br />Dilatation angle: the change in the orientation of grains on a shear plane<br />Post failure behavior<br />Potential function<br />Dilatation angle<br />Footing properties:<br />6 cm width square<br />Soil properties:<br />E = 27 MPa<br />υ = .35<br />C ~ 0 kPa<br />Φ = 38.1 deg<br />elastic<br />plastic<br />
  • 12. 3ed season:<br />Numerical vs experimental results<br />Footing properties:<br />12 cm width square<br />Soil properties:<br />Ψ=?<br />E = ?<br />υ = ?<br />C ~ 0 kPa<br />Φ = 38.1 deg loose sand<br />Φ = 42.1 deg dense sand<br />Dense sand:<br />Loose sand:<br />E : 65 &lt; 70 &lt; 98 MPa<br />E : 35 &lt; 36 &lt; 59 MPa<br />Ψ : 4 &lt; 7.6 Deg<br />Ψ : 5 &lt; 12.6 Deg<br />
  • 13. 3ed season:<br />Numerical vs experimental results<br />Footing properties:<br />Cross shape footing with different sizes<br />Soil properties:<br />Same as the parameters for square foundations<br />
  • 14. 3ed season:<br />Numerical vs experimental results:<br />Footing properties:<br />H shape foundations with different sizes<br />Soil properties:<br />Same as the parameters for square foundations<br />
  • 15. 4th season: analysis of the results<br />Introduction<br />Who to separate different shear areas under the footing?<br />Orientation of displacement vectors are different in each zone<br />Interfering foundations:<br />1- interference increase in bearing capacity<br />Blocking is happened<br />2- bearing capacity of too far or too near footings will increase less.<br />Interference is more efficient<br />No interference between shear zones<br />
  • 16. 4th season:<br />Cross shape foundations<br />Soil properties:<br />Dense sand<br />Ψ=5<br /> E = 70 MPa<br />υ= .35<br /> C ~ 0 kP<br />Φ= 42.1 deg<br />Loose sand<br />Ψ=4<br /> E = 36 MPa<br />υ= .3<br /> C ~ 0 kP<br />Φ= 38.1 deg<br />Decrease in ratio of B/L difference in bearing capacities<br />
  • 17. 4th season:<br />Cross shape foundations<br />Cross shape foundation with large ratio of B/L:<br />
  • 18. 4th season:<br />Cross shape foundations<br />Cross shape footing with proper ratio of B/L<br />Coefficients have their maximum value <br />
  • 19. 4th season:<br />Cross shape foundations<br />Cross shape foundation with small ratio of B/L<br />
  • 20. 4th season:<br />Optimum ratio of B/L<br />Maximum value of q/A<br />Reduction of q/A due to blocking effect<br />There is no interference between two parts of the footing<br />
  • 21. 4th season:<br />H shape foundations<br />Soil properties:<br />Dense sand:<br />Ψ=5<br /> E = 70 MPa<br />υ= .35<br /> C ~ 0 kP<br />Φ= 42.1 deg<br />Loose sand:<br />Ψ=4<br /> E = 36 MPa<br />υ= .3<br /> C ~ 0 kP<br />Φ= 38.1 deg<br />Decrease in ratio of B/L difference in bearing capacities<br />
  • 22. 4th season:<br />H shape foundations<br />H shape foundations with large ratio of B/L<br />
  • 23. 4th season:<br />H shape foundations<br />H shape foundation with proper ratio of B/L <br />Coefficients have their maximum value <br />
  • 24. 4th season<br />H shape foundation<br />H shape foundation with small ratio of B/L<br />
  • 25. 4th season<br />Optimum value of B/L<br />Maximum value of q/A<br />Reduction of q/A due to blocking effect<br />There is no interference between two parts of the footing<br />
  • 26. 4th season<br />H shape Vs cross shape foundations<br />
  • 27. 4th season<br />Uplift of soil around the multi edge foundations<br />No uplift due to blocking effect<br />
  • 28. Results<br />Maximum bearing capacity of multi edge foundations are more than bearing capacity of square foundations when they have the same area<br />Interference of shear zones under multi edge foundations have a significant effect on their bearing capacity<br />Ratio of dimensions of a multi edge foundation has a remarkable effect on its bearing capacity<br />In H shape foundations, the displacement of shear zones is not symmetric due to unequal width of interfering parts<br />In multi edge foundations there is no uplift of soil in the concave corners of the foundation<br />

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