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Interfacial friction between soils and solid surfaces

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1 Interfacial friction between soils and solid surfaces
Dr. R. G. Robinson Assistant Professor Department of Civil Engineering IIT Madras

2 Shallow foundation Deep foundation Typical field situations
Tip resistance Deep foundation

3 Typical field situations
Retaining walls

4 Reinforced earth walls
Typical field situations Reinforced earth walls

5 Geosynthetic reinforced earth slopes
Typical field situations Geosynthetic reinforced earth slopes

6 Typical field situations
Geotextiles

7 Definition of coefficient of friction and friction angle
P P Normal Force T Shear Force Coefficient of friction, m=tand=T/P where, d is the friction angle T Soil Solid material P Shear stress = T/A T Normal stress=P/A

8 Apparatus used for evaluating friction angle
Potyondy (1961) Rowe (1962) Silberman (1961) Ingold (1984) Ingold (1984)

9 Apparatus used for evaluating friction angle
Jewell and Wroth (1987) Murthy et al. (1993) Coyle and Sulaiman (1967)

10 Brumund and Leonards (1973)
Apparatus used for evaluating friction angle Brumund and Leonards (1973) Ingold (1984) Heerema (1979) Yoshimi and Kishida (1981)

11 Abderrahim and Tisot (1993)
Apparatus used for evaluating friction angle Desai et al. (1985) Uesugi and Kishida (1986) Paikowsky et al. (1995) Abderrahim and Tisot (1993)

12 Some Terminologies

13 Three Phases in Soils S : Solid Soil particle W: Liquid Water
A: Air Air Void ratio, e = Vv/Vs Water content, w = Mw/Ms

14 Relative Density (Dr) Loosest Densest emax = 0.92 emin = 0.35
(Lambe and Whitman, 1979)

15 Particle shapes-- Sand
Coarse-grained soils Rounded Subrounded Subangular Angular (Holtz and Kovacs, 1981)

16 Maximum and minimum void ratio
ASTM D 4253; ASTM D 4254 Minimum void ratio Maximum void ratio

17 Direct shear test tf shear strength of soil sn Normal stress
c cohesion intercept f angle of internal friction

18 Typical direct shear test results
Dense sand Loose sand f fcv sn1 sn2 sn3 Displacement Displacement sn1 Angle of repose sn2 sn3 Fcv ~ Angle of repose

19 Interface friction in sands

20 Factors influencing interfacial friction angle of Sand
Surface Roughness Density of sand Normal stress Rate of deformation Size of apparatus Grain size and shape Type of apparatus

21 Influence of sand density and surface Roughness
Toyoura sand Soma sand

22 Influence of sand density……
Results of triaxial and soil-steel friction tests (after Noorany, 1985) Soil Type Soil Condition   Silica sand loose dense 35 40 21 20 Calcareous sand from Guam loose, crushed loose, ground dense, crushed 46 49 48 18 - 22 Calcareous sand from Florida medium medium, crushed medium, ground 44 45 47 23

23 Influence of sand density……
Acar et al. 1982 Levacher and Sieffert 1984

24 I Maximum Values: Limiting values of d
Potyondy (1961), Panchanathan and Ramaswamy (1964), Uesugi and co-workers reported the limiting maximum value of d is the peak angle of internal friction fp Yoshimi and Kishida (1981) report that the maximum limiting value is the critical state friction angle fcv

25 Minimum Values of  Reported by Various Authors
Interface  Source Sand-material Sand-smooth surface Sand-smooth material Sand-normal glass Sand-pyrex glass Sand-stainless steel Sand-steel Glass beads-steel Material-Material Diamond-diamond Sapphire-sapphire Metal-diamond Steel-sapphire  0.5  7 - 10 5 – 6 7 tan -1 (0.07/Ri) § 5 3 11 Lambe and Whitman (1969) Yoshimi and Kishida (1981) Tatsuoka and Haibara (1985) Uesugi and kishida (1986b) Tejchman and Wu (1995) Paikowsky et al. (1995) Bowden and tabor (1986) Notes:   Particle-to particle friction angle § Ri Modified roundness

26 Influence of normal stress
Potyondy (1961); Acar (1982): Both δ and Φ decreases with normal stress but the ratio (δ/f) remains constant Heerema (1979), Uesugi and Kishida (1986), O’Rourke et al. (1990) d is independent of normal stress For soft materials: d increases with normal stress due to indentation of sand into the material (Panchanathan and Ramaswamy, 1964; Valsangkar and Holm (1997)

27 Influence of Rate of deformation
Heerema (1979) Rate of deformation from 0.7 to 600 mm/s No influence Lemos (1986) Rate of deformation to 133 mm/min

28 Influence of Size of apparatus
Brumund and Leonards (1973) Rods with interface area of 225 cm2 and 400 cm2 No appreciable difference Uesugi and kishida (1986) Simple shear apparatus, 40 cm2 and 400 cm2 No influence O’Rourke et al (1990) Direct shear apparatus of size equal to 6cm x 6 cm, 10 cm x10 cm, 28 cm x28 cm and 30.5x30.5 cm No significant influence

29 Influence of grain size and shape
Rowe (1962) Rowe (1962), Uesugi and Kishida (1986), Jardine and Lahane (1994): d decreases with increase in grain size Friction angle (degrees) Particle diameter (mm) Angular particles give higher friction angle (Uesugi and Kishida 1986; O’Rourke et al. 1990; Paikowski et al. 1995)

30 Influence of type of apparatus
Kishida and Uesugi (1987) Simple shear versus direct shear No difference Thandavamurthy (1990) Direct shear versus model pile tests Direct shear gives 20% higher Abderrahim and Tisot (1993) Direct shear- Ring torsion-Pressuremeter probe Direct shear > Pressuremeter probe >Ring shear

31 QUANTIFICATION OF INTERFACE ROUGHNESS

32 d versus Roughness (Bosscher and Ortiz 1987)

33 Normalized Roughness (Kishida and Uesugi 1987)

34 Correlation with Normalized Roughness (Kishida &Uesugi 1987)

35 Definition of modified roundness (Uesugi and Kishida 1986)
Modified roundness of a particle

36 Correlation between m, Rn and R
(0.27) (0.19) (0.17)

37 Summary of some published interface friction tests
Author(s) Type of testing apparatus Results of investigation Potyondy (1961) Direct shear apparatus with the sand on the top of test material d increases with density and dlim=fp Broms (1963) Direct shear mode by sliding the material over the sand A d value of 23o was obtained irrespective of sand density Yoshimi and Kishida (1981) Ring shear with the test material on top of sand Density has no influence and dlim=fcv Acar et al. (1982) Similar to Potyondy d increases with density Noorany (1985) Similar to Broms Influence of density is negligible Uesugi et al. (1990) Simple shear with the sand on top of the test material d increases with density dlim=fp

38 Analysis of past studies
From the review the following three conclusions can be drawn: d increases with surface roughness and reaches a maximum limiting value For very rough surfaces, d tends to a limiting maximum value which could be either the peak angle of internal friction fp or the critical state friction angle fcv. d can either increase or remain constant with the increase in sand density.

39 Summary of some published interface friction tests
Author(s) Type of testing apparatus Results of investigation Potyondy (1961) Direct shear apparatus with the sand on the top of test material d increases with density and dlim=fp Broms (1963) Direct shear mode by sliding the material over the sand A d value of 23o was obtained irrespective of sand density Yoshimi and Kishida (1981) Ring shear with the test material on top of sand Density has no influence and dlim=fcv Acar et al. (1982) Similar to Potyondy d increases with density Noorany (1985) Similar to Broms Influence of density is negligible Uesugi et al. (1990) Simple shear with the sand on top of the test material d increases with density dlim=fp

40 Schematic of Type A and Type B apparatus
Loading cap SAND SAND Material Type A apparatus Type B apparatus

41 Features of Type A and Type B apparatus
Sl.No. Features Type A Type B I Apparatus configuration 1 2 3 Relative position of solid material and sand and sample preparation. Application of normal stress to the interface. Apparatus type in literature Soild material is on the top of sand. The sand specimen is prepared first and the solid surface is placed over the prepared leveled surface. Normal stress is applied through the material to the interface. Ring torsion apparatus, direct shear apparatus by sliding solid material over sand. The sand specimen is on the top of solid material surface. The sand is prepared directly on the solid surface. Normal stress is applied through the sand the interface. Direct shear apparatus by sliding soil over solid material, simple shear apparatus, translational test box etc.

42 ….. Features of Type A and Type B apparatus
Sl.No. Features Type A Type B II Influence of type of apparatus on the results obtained 4 5 6 Influence of roughness Influence of density of sand. Maximum limiting value of   increases with roughness Negligible. The maximum limiting value for very rough interface is critical state of angle of internal friction of sand increases with roughness. increases with the increase of density. The limiting maximum value is the peak angle of internal friction of sand.

43 Experiments in Direct shear apparatus

44 Solid materials used Material 1– Stainless steel

45 Material 2– Mild steel Material 3– Mild steel

46 Material 4– Ferrocement

47 Surface profiles of the materials
Stainless steel Mild steel Mild steel Concrete surface Concrete surface

48 Grain size distribution curves of the sands used

49 Properties of sands used
Sand No. Gs D50 mm Cu Dav (d)max kN/m3 (d)min 1 2 3 4 5 6 7 2.64 2.65 1.60 1.10 0.74 0.42 0.27 0.78 2.20 1.3 1.5 1.4 1.6 3.4 8.3 1.53 1.01 0.69 0.41 1.92 15.9 16.0 16.1 16.2 18.0 18.6 13.0 12.9 13.1 14.0 14.5 Note: Gs Specific gravity of soil grains (d)max Maximum dry density (d)min Minimum dry density

50 Raining Technique--Calibration curves

51 Schematic of Type A apparatus

52 Type A apparatus

53 Schematic of Type B apparatus

54 Type B apparatus

55 Typical shear stress-movement curves
Sand 6, s’n = 140 kPa Type B Type A

56 Sand 4 Material 5 sn’ = 70 kPa

57 Typical failure envelopes (Type B)
Peak Critical state

58 (dpB/f) versus Relative density (Type B)
Thandavamurthy (1990)

59 Variation of (dpB/f) with Dav (Type B)

60 Proposed Roughness index
Relative Roughness (R) Ra Average Roughness Dav Average particle size

61 Variation of (dpB/f) with R

62 Variation of dcvB with R

63 Comparison of dcvA with dcvB

64 Drained shear strength of fine-grained soil-solid surface interfaces

65 Clays are sheet like and possess plasticity characteristics

66 Grain size distribution curves of the soils used

67 Properties of cohesive soils used
Property Soil Red Earth Kaolinite Illite Atterberg Limits Liquid limit (%) Plastic Limit (%) Plasticity index (%) Grain Size Sand (%) Silt size (%) Clay size (%) Average particle size (m) Coefficient of consolidation, Cv (cm2/sec) 33 19 14 44 47 9 88.4 1.09 x 10 -3 55 22 80 20 12.0 1.37 x 10 -2 131 78 53 36 64 8.5 4.59 x 10 -4

68 Variation of shear stress with deformation rate of illite

69 Deformation rate (mm/min.)
Deformation rates calculated and adopted for tests under drained condition Soil Deformation rate (mm/min.) Calculated Adopted Red Earth Kaolinite Illite 0.05 0.63 0.02 0.25

70 Failure envelope of a soil at constant preconsolidation pressure
fnc f’ p’c OC NC Normal stress Shear stress Failure envelope of a soil at constant preconsolidation pressure

71 FAILURE ENVELOPE WITH CONSTANT OCR
Red earth OCR=1 sn’=100, 200 and 300 kPa OCR=5 s’p=500 kPa s’n = 100 kPa s’p=1000 kPa s’n = 200 kPa s’p=1500 kPa s’n = 300 kPa OCR=10 s’p= 500 kPa s’n = 50 kPa s’p=1000 kPa s’n = 100 kPa s’p=1500 kPa s’n = 150 kPa Illite

72 Typical shear stress-movement curves
2 4 6 8 Shear movement, mm Shear movement, mm

73 Typical failure envelopes
Normal stress Normal stress

74 Variation of D’B and (D’B/F’) with OCR
DBo DB/F

75 Variation of (DB/F) with Ra

76 Variation of (DB/F) with R

77 Comparison of D values from Type A and Type B

78 SUMMARY Interfacial friction depends on mode of shear for sands and the maximum value of friction angle is controlled by the type of apparatus used to evaluate the friction angle For clays, mode of shear has no influence

79 Research Issues Modeling of interface behaviour : shear stress-movement curves Roughness Hardness of solid material Rigidity of materials Mode of shear Particle size and shape

80 Acknowledgements Prof. K. S. SUBBA RAO Department of Civil Engineering
IISc, Bangalore 2. Prof. M. M. Allam CSIR for funding

81 Thank you


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