1.Pile foundations 2021 (1).pptx

pile

1. PILE FOUNDATION By – C.M.GUPTA Sr.Prof /Br.2 IRICEN 1

2. TYPE OF FOUNDATIONS SHALLOW SINGLE FOOTING COMBINED FOOTING RAFT STRIP DEEP PILE WELL 2

3. DEEP FOUNDATIONS ADEQUATE GRIP- BELOW DEEPEST ANTICIPATED SCOUR DEPTH OF FOUNDATION BELOW WATER LEVEL FOR Q f – NOT LESS THAN 1.33 X MAX DEPTH OF SCOUR SHALL NOT REST ON SLOPING ROCK STRATA DYNAMIC AUGMENT NEED NOT BE CONSIDERED 3

4. CLASSIFICATION OF PILES BROAD CALSSIFICATION DRIVEN (DISPLACEMENT PILES) BORED (REPLACEMENT PILE) ON THE BASIS OF MATERIAL TIMBER STEEL PCC RCC PSC COMPOSITE 4

5. CLASSIFICATION OF PILES Method of construction Driven precast piles Driven cast in situ piles Bored precast piles Bored cast in situ piles Mode of load transmission End bearing piles Friction piles Friction cum end bearing piles 5

6. CLASSIFICATION OF PILES Sectional area Circular Square Tubular Octagonal H-section Size Micro (mini) piles (<150 mm) Small diameter pile (>150 mm < 600 mm) Large diameter pile (>600 mm) 6

7. CLASSIFICATION OF PILES INCLINATION VERTICAL PILES RAKER (BATTER PILES) 7

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10. END BEARING PILE 10

11. FRICTION PILES 11

12. DRIVEN PILING 12

13. BORED PILING 13

14. CONSTRUCTION OF PILE FOUNDATION Driven precast piles Driven cast in situ piles Bored cast in situ piles 14

15. Driven precast piles 15 Drop hammer Single/ double acting hammer Diesel hammer Vibratory hammer

16. Driven cast in situ Piles Steel casing pipe with shoe at bottom driven to reqd depth Casting after placing reinforcement cage 16

17. Bored cast in situ piles Guide casing of 3-4 m at top of bore hole Bailer – chiesel Bentonite slurry for stabilisation Flushing Concreting after placing rein. cage Tremie method of concreting Concrete grade m 20 or higher High slump concrete 17

18. INSTALLATION OF BORED CAST IN SITU PILES BAILER AND CHISEL METHOD AUGUR BORING BORING USING OSCILLATORS VIBRATORY DRILLING RIGS 18

19. BAILER AND CHISEL METHOD 19

20. AUGAR BORING 20

21. UNDER REAMING RIG 21

22. BORED CAST IN SITU PILES Stabilization of bore Drilling Mud Circulation (Bentonite Slurry) Bentonite is impure clay consisting of Montmorillonite. Na cation responsible for support 22

23. MUD CIRCULATION 23

24. TREMIE CONCRETING concrete to be rich in cement (min 370 kg/ m 3 ), slump – 150 -180 mm casing- temp/permanent sliding plug/steel plate flushed ahead of first charge – to prevent mixing of water hopper and tremie should be closed system dia of tremie pipe – 200mm for 20mm aggregare concreting to be uninterrupted top of concrete in pile – above cutoff level min embedment in pile cap – 50 mm 24

25. TREMIE CONCRETING 25

26. TREMIE CONCRETING 26

27. Method statements for casting of piles 27

28. Method statements for casting of piles 28

29. Method statements for casting of piles 29

30. Method statements for pile cap casting 30

31. Method statements for pile cap casting 31

32. Method statements for pile cap casting 32

33. SELECTION OF TYPE OF PILES Availability of space and head room Proximity to structures Reliability – driven precast better Limitation of length- driven piles – 25 - 30 m 33

34. SOCKETTING IN ROCK For the end bearing piles Sound relatively homogenous rock including granite and gneiss -- 1 to 2D Moderately weathered closely formed including schist & slate ---- 2 to 3D Soft rock --- 3 to 4D 34

35. SEQUENCING OF PILING Normally from centre to periphery or from one side to other Possibility of harm to adjacent piles be considered. More damage in compact soils Order of installation should avoid creating a compacted block of ground In stiff clay or compacted sand layers – from center to outward or from one edge to across the group In very soft soils – from outside to inside 35

36. SPACING OF PILES Determined based on the Type of soil Empirical approach Practical aspects of installing a pile Nature of load transfer Possible reduction in bearing capacity of a group of piles 36

37. SPACING OF PILES For end bearing piles Governed by competency of bearing strata Not less than 2.5 D For friction piles Sufficiently apart to avoid overlapping zones Not less than 3 D Closure spacing possible in loose sand or fillings for driven piles only Max spacing 4 D 37

38. LOAD CARRYING CAPACITY OF PILE In context of foundation engineering Load that a pile can carry without undergoing continuous settlement for insignificant load increments – by virtue of its boundary conditions Failure of surrounding soil occurs before failure of pile material 38

39. FACTORS INFLUENCING PILE CAPACITY Surrounding soil Installation technique Spacing of piles Symmetry of the group Location of pile cap Shape of pile cap Location of pile in a group Drainage conditions in soil 39

40. LOAD CARRYING CAPACITY OF SINGLE PILE Dynamic pile formula – by using the data obtained during piling ( conservation of energy) Hiley’s Formula More reliable for non-cohesive soils Not reliable for cohesive soils Static formula – using soil test results Load test – after 4 weeks of casting of pile Resistance due to skin friction available only below scour line Drag down force 40

41. Engineering news formula 41

42. Hileys formula 42

43. LOAD CARRYING CAPACITY Annex B-1 of IS:2911 Part 1, Sec.2:2010 - For Granular soil Area of pile toe Dia of pile cm Density of soil Bearing capacity factors Effective overburden pressure at toe Coefficient of earth pressure Effective overburden pressure at ith layer Angle of wall friction = phi Surface area of ith layer SEE fig 1 of appendix B for Nq And IS 6403 for Nr (slide 22) Similar formula for clayey soil is also given in Annex B-2 43

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45. Bearing capacity factor N γ 45

46. 46 Bearing capacity factor N q

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51. FACTOR OF SAFETY THE MINIMUM FOS – 2.5 FOR STATIC FORMULA MINIMUM FOS – 2 FOR LOAD TEST 51

52. BEARING CAPACITY OF A PILE GROUP MAY BE EQUAL TO THE BC OF SINGLE PILE X NO. OF PILES LESS THAN THE ABOVE FRICTION PILES, CAST OR DRIVEN INTO PROGRESSIVELY STIFFER MATERIALS & END BEARING PILES – EQUAL FRICTION PILES INSTALLED IN SOFT AND CLAYEY SOILS – LESS DRIVEN PILES IN LOOSE SANDY SOILS – MORE DUE TO EFFECT OF COMPACTION 52

53. BEARING CAPACITY OF A PILE GROUP STRATA TYPE OF PILE BC PF PILE GROUP 1. DENSE SAND NOT UNDERLAIN BY WEAK DEPOSITS DRIVEN NO. OF PILES X SPC 2. LOOSE SANDY SOILS ½ (NO. OF PILES X SPC) 3. SAND NOT UNDERLAIN BY WEAK DEPOSITS BORED ⅔ (NO. OF PILES X SPC) SPC – SINGLE PILE CAPACITY FOR PILES DRIVEN INTO SOFT OR MEDIUM CLAYS WITH 3 TO 4 D SPACING – ULTIMATE GROUP CAPACITY = ⅔ OF THE SUM OF SINGLE PILE CAPACITY 53

54. PERMISIBLE TOLERANCE FOR PILES ALIGNMENT CONTROL VERTICAL PILES – DEVIATION OF 1.5% RAKER PILES – DEVIATION OF 4% SHIFT FOR PILES LESS THAN OR EQUAL TO 600 MM DIA NOT MORE THAN 75 MM OR D/4 WHICHEVER IS LESS FOR MORE THAN 600 MM. DIA. PILES 75 MM OR D/10 WHICHEVER IS MORE EXCESS DEVIATION BEYOND DESIGN LIMITS –PILE TO BE REPLACED OR SUPPLEMENTED BY ADDITIONAL PILES 54

55. OVERLOADING OF PILES 10% OF THE PILE CAPACITY MAY BE ALLOWED ON EACH PILE MAX OVERLOADING ON A GROUP SHALL BE RESTRICTED TO 40% OF THE ALLOWABLE LOAD ON A SINGLE PILE SHALL NOT BE ALLOWED AT INITIAL DESIGN STAGE 55

56. LOAD TEST STRESS TEST MAINTAINED LOAD TEST CONSTANT RATE OF PENETRATION TEST LATERAL LOAD TEST DYNAMIC LOAD TEST CYCLIC LOAD TEST STRAIN TEST LOW STRAIN INTEGRITY TEST HIGH STRAIN INTEGRITY TEST 56

57. PILE LOAD TESTING (IS-2911 PART-IV) Initial Test Purpose Determination of ultimate load capacity and arrival at safe load by application of factor of safety, To provide guidelines for setting up the limits of acceptance for routine tests, To get an idea of suitability of piling system, and To have a check on calculated load by dynamic or static approaches. 57

58. PILE LOAD TESTING (IS-2911 PART-IV) The number of initial tests may be selected as given below depending upon the nature of sub-strata, number of piles and past experience at the site. For small size projects (for piles less than 1 000 numbers), a minimum of two tests. For large size projects (for piles more than 1 000 numbers), a minimum of two tests for first 1 000 piles and additional one test for every additional 1 000 piles and part thereof. The frequency of testing stipulated above is applicable for each diameter of pile and rated capacity of pile in each type (mode) of loading. The number of tests may be increased/decreased depending upon whether the strata is erratic/uniform, subjected to a minimum of two tests. 58

59. PILE LOAD TESTING (IS-2911 PART-IV) Routine Test On ½ percent of piles, can be increased to 2% depending on strata Purpose Checking the safe load as determined from static analysis Detection of any unusual performance contrary to the findings of the initial test, if already done; and Workmanship. 59

60. PILE LOAD TESTING (IS-2911 PART-IV) Routine Test The piles to be tested for routine tests may preferably be selected on the basis of the following: Abnormal variation in concrete consumption. Sudden drop in concrete level during construction of piles. Problems encountered during boring and tremie operation. Significant variation in depth of pile with respect to other adjoining piles and boring record. Anomalies observed during the driving operation in case of driven piles. Piles under sensitive locations of structures. Any doubt arising from non destructive test results. 60

61. PILE LOAD TESTING (IS-2911 PART-IV) VERTICAL LOAD TEST Maintained load method Cyclic load test ( To separate skin friction and end bearing ) CRP test (Uniform penetration) LATERAL LOAD TEST PULL OUT TEST 61

62. LOAD TEST- INITIAL TEST The safe load on a single pile will be least of the following For piles dia upto 600 mm Two third of the final load at which total displacement attains a value of 12 mm 50 % of the final load at which the total displacement equals 10 % of the dia. of pile and 7.5% of bulb dia in case of under reamed piles For piles dia more than 600 mm Two third of the final load at which total displacement attains a value of 18 mm or 2% of dia whoever is less 50 % of the final load at which the total displacement equals 10 % of the dia. of pile and 7.5% of bulb dia in case of under reamed piles 62

63. LOAD TEST - INITIAL THE SAFE LOAD FOR GROUP OF PILES FINAL LOAD AT WHICH TOTAL DISPLACEMENT IS 25 MM TWO THIRD OF FINAL LOAD AT WHICH DISPLACEMENT IS 40 MM 63

64. LOAD SETTLEMENT CURVE SAFE LOAD Least of 2/3 P1 or ½ P2 FOR GROUP Least of Load corrp. to 25 mm sett or 2/3 corrp. to 40 mm sett. LOAD IN INCREMENTS OF 20% Final load maintained for 24h 64

65. LOAD TEST – ROUTINE TEST Test load will be atleast 1.5 times the working load Max. settlement should not > 12 mm for piles dia upto 600 mm 18 mm or 2 percent of pile diameter whichever is less for piles of diameter more than 600 mm. for group of piles max. Settlement should not > 25 mm 65

66. STATIC LOAD TEST 66

67. PILE LOAD TEST ( KENTELEDGE ARRANGEMENT ) 67

68. PILE LOAD TEST ( WITH ANCHOR PILES) 68

69. DYNAMIC PILE TESTING SUPPLEMENTS STATIC TESTING HIGH STRAIN TESTING PROVIDES DATA ON FORCE & ACCELERATION OF PILE EVALUATION OF BEARING CAPACITY FACILITATE IMMEDIATE DECISION ABOUT ACCEPTANCE OR REJECTION OF PILE LOW STRAIN TESTING FOR TESTING CONTINUITY OF PILE INFORMATION ABOUT DIMENSIONS AND CONSISTANCY OF MATERIAL ASTM D 4945 69

70. DYNAMIC PILE TESTING as per ASTM D 4945 70

71. DYNAMIC PILE TESTING 71

72. DEFECTS IN CAST IN SITU PILES HONEY COMBING DUE TO INADEQUATE VIBRATIONS SEGREGATION DUE TO IMPROPER CONCRETE PLACEMENT METHODS WASHOUT OF CEMENT DUE TO GROUNDWATER FLOW CRACKS IN PILE SHAFT DUE TO SHRINKAGE INCLUSION OF FOREIGN MATERIAL NECKING DUE TO COLLAPSE OF SIDE WALLS DURING WITHDRAWAL OF TEMPORARY CASING 72

73. NECKING IN PILE 73

74. NECKING IN PILE 74

75. THANK YOU 75