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Shallow Foundation

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Its a group Presentation on Shallow foundation .(2.2 semester)

Veröffentlicht in: Ingenieurwesen

Shallow Foundation

  1. 1. GROUP NO.01 Name Roll No. (1) Raktim Barua 10.01.03.123 (2) Farjana Akter 10.01.03.140 (3) Fatema Sultana 10.o1.03.159 (4) Md.Shahadat Hossain 10.01.03.154 (5) Raiyan Fardous Ratul 10.01.03.153 (6) Sajjad Hossain 10.01.03.152 (7) Mehrana Rashid Noor 10.01.03.162 (8) Tuhin 10.01.03.156 (9) Bushra Tasnim 09.02.03.002
  2. 2. Foundation: Foundation is the lowest part of a structure which  provides a base for the super‐structure and transmit the loads  (live load, wing load) on the structure including the dead weight  of the structure itself  to the soil below.   Types of Foundation: Foundation can be broadly classified into two types– 1. Deep Foundations  2. Shallow Foundations
  3. 3. Shallow foundations: Foundation is placed immediately lowest part of the  super structure, is termed as Shallow foundation. Why we use shallow foundation? ‐ To distribute the structural loads over a wide  horizontal area at a shallow depth below the ground  level.
  4. 4. The various types of shallow foundations are :  (a) Spread footing (b) Combined footing (c) Mat or Raft foundation. (d) Grillage footing (e) Eccentrically loaded footing
  5. 5. Spread footings  Spread footings  are  structural members used  to support columns and  walls and to transmit and  distribute their loads to  the soil.
  6. 6. Types of spread footing  Wall footings  Reinforced concrete  footings  Inverted arch footing  Column footings
  7. 7. Wall Footing
  8. 8.  Support  walls that  may be either bearing  or nonbearing walls.  Commonly  required  to support direct  concentric loads. Why Wall Footing?
  9. 9. Footings carry  relatively light loads on  well drained cohesive  soil. A wall footing under  concentric load behaves  similarly  to a cantilever   beam. Used in low rise  buildings. Why Wall Footing?
  10. 10. Reinforced concrete footing
  11. 11. Why Reinforced concrete footing? Relatively heavy loading  than wall footing. Bearing capacity of the  soil is low. 
  12. 12. In a reinforced concrete  wall footing, the  behavior is identical to  that of wall footing. Reinforcing steel is  placed in the bottom of  the footing in a direction  perpendicular to the wall  like a reinforced concrete  beam or slab. Why Reinforced concrete footing?
  13. 13. Inverted arch footing
  14. 14. When a wall is composed of isolated piers, it is well to combine all their footings into one, and to step the piers down . Inverted arch footing
  15. 15. COLUMN FOOTINGS
  16. 16. WHY COLUMN  FOOTINGS?   This is one of the most  economical types of  footings.   Used when columns are  spaced at relatively long  distances.
  17. 17. WHY COLUMN  FOOTINGS?   Low bending  strength.  When bearing  capacity of soil is  good.                                                                                  Carry heavy loads.  Used to support  single columns. To distribute the load  uniformly.
  18. 18. CHARACTERISTICS  OF COLUMN  FOOTINGS  Constructed with brick,  stone or plane  concrete.  Circular, rectangular or  square in plan.
  19. 19. PROCEDURE OF COLUMN  FOOTINGS EARTHWORK LEVELING
  20. 20. Support Brick flat soling 9’X9’ Wooded Frame 3”BRICK FLAT SOLING
  21. 21. Joint of rod Wires   BINDING THE RODS
  22. 22. Upper rod Inner rod 6” interval POSITION OF RODS PLAN
  23. 23. 3”Clear cover 6”Block CLEAR COVERS & BLOCKS
  24. 24. Centering with plumb bob Ring Centre point of column CENTERING  THE COLUMN
  25. 25. 6” Interval ring PREPARED COLUMN REINFORCEMENT
  26. 26. Length 17” Width 9” LENGTH & WIDTH OF RING
  27. 27. PUTTING THE COLUMN INTO THE FOOTING
  28. 28. Load bearing support CAVING TENDENCY
  29. 29. LEVELLING THE COLUMN SUPPORTING THE COLUMN
  30. 30. Vibrating  PORING CEMENT CONCRETE 
  31. 31. A  COMPLETE  COLUMN  FOOTING
  32. 32. Combined footings Combined  footings usually support two  columns, or three columns  not in a row.  Combined footings are  used when tow columns  are so close that single  footings cannot be used or  when one column is  located at or near a  property line.
  33. 33. When two columns  are close together,  causing overlap of  adjacent isolated  footings. When soil bearing  capacity is low, causing  overlap of adjacent  isolated footings. WHY COMBINED FOOTINGS?
  34. 34. PROCEDURE OF COMBINED FOOTINGS
  35. 35. A COMPLETE COMBINED FOOTING
  36. 36. Foundation which consists of  thick reinforced concrete slab  covering the entire area of the  bottom of the structure like a floor. This foundation was invented by  John Root at Chicago in 19th century.  Raft Foundation
  37. 37. Why Raft Foundation? Base soil has low bearing  capacity or the column loads are  so large that more than 50% of  the area is covered by  conventional spread footings. Resist unequal settlement due to  earthquake.  Quickness of the construction  work.
  38. 38. Figures of the Different Types of Raft
  39. 39. PROCEDURE OF MAT FOUNDATION Plan Shoring Excavation of soil Brick flat soling                  or C.C. casting Formwork &  Placing of  reinforcement  Casting Curing
  40. 40. Before earth can be excavated to make the foundation certain precaution has to be taken to stop the outside soil from caving in the excavated area. These precautions are called shoring , the purpose of which is to anyhow retain the surrounding soil. Shoring  process
  41. 41. Excavation Excavate earth according to design specification
  42. 42. Reinforced chair Bottom rebar Top rebar POSITION OF  REBARS
  43. 43. PREPARED COLUMN  REINFORCEMENT SUPPORTING THE COLUMN Extra top rebar
  44. 44. Position of column on foundation Support Column
  45. 45. Formwork for casting Wooden frame Support
  46. 46. Pouring cement  concrete &  compacting 
  47. 47. Spread footers being installed too shallow, oftentimes just 2‐3 feet below a foundation, which does not eliminate the effects of expansive soils. Foundation repair will last longer than a week as the excavations are made and the concrete will have to be cured before the holes can be refilled. Limitations of shallow foundation
  48. 48. A huge amount of earthwork is to be done in Mat foundation. If the shoring system can not resist the pressure of outside land, then the structure surrounding the area may be damaged by deflection of soil. Ground water may come out when the earthwork is done. Limited to dealing with point loads. Limitations of shallow foundation
  49. 49. It is a quick process compared to others in the construction work. This type of foundation is also economically cheaper than any other foundations. Though there are some limitations in mat foundation still it is economical in some cases. Advantages of shallow foundation
  50. 50. It can resist ground water absorption. The damage due to earthquake is lesser than any other type of foundation. It consists of a reinforced concrete slab  which is more thicker than footing  foundation. It prevents unequal settlements. Advantages of shallow foundation
  51. 51. We know shallow foundations are not applicable  for high rise structures, but we saw a lot of high  rise structures which are building upon raft  foundation! Generally Raft is used when the bearing capacity  of soil is low, but in some sites, we saw raft  foundation is used instead of having a good  bearing capacity! Conflicts of Our Knowledge with Our Experiences
  52. 52. Questions ? ?

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