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Behavior of Vertically Confined Square Footing on Reinforced Sand under Centric Inclined Loading

B. Kirtimayee
B. Kirtimayee
 and 
Narendra Kumar Samadhiya
Narendra Kumar Samadhiya
   | Jul 27, 2022
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Article Category: Original Study
Published Online: Jul 27, 2022
Page range: 224 - 238
Received: Nov 26, 2021
Accepted: May 20, 2022
DOI: https://doi.org/10.2478/sgem-2022-0012
Keywords
© 2022 B. Kirtimayee et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1

Schematic diagram of the experimental set up.
Schematic diagram of the experimental set up.

Figure 2

Particle size distribution curve.
Particle size distribution curve.

Figure 3

Geogrid used in the experimental study as (a) confiner (b) reinforcement.
Geogrid used in the experimental study as (a) confiner (b) reinforcement.

Figure 4

Schematic presentation of footing with (a) confiner (b) confiner with reinforcements under centric inclined load.
Schematic presentation of footing with (a) confiner (b) confiner with reinforcements under centric inclined load.

Figure 5

Experimental set up for 5° angle of inclination.
Experimental set up for 5° angle of inclination.

Figure 6

Load intensity-settlement behavior of footing with confiner at 5° angle of inclination for (a) D/B=1.0 (b) D/B=1.5 (c) D/B=2.0 with variation of d/B=1.0,1.5,2.0 respectively.
Load intensity-settlement behavior of footing with confiner at 5° angle of inclination for (a) D/B=1.0 (b) D/B=1.5 (c) D/B=2.0 with variation of d/B=1.0,1.5,2.0 respectively.

Figure 7

Load intensity-settlement behavior of footing with confiner (D/B=2.0;d/B=2.0) and reinforcement (a) 5° (b) 10° (c) 20° angle of inclination.
Load intensity-settlement behavior of footing with confiner (D/B=2.0;d/B=2.0) and reinforcement (a) 5° (b) 10° (c) 20° angle of inclination.

Figure 8

Variation of ultimate load intensity with normalized (a) depth of confiner at D/B = 1.0 (b) top surface dimension of confiner at d/B = 2.0 for footing with confiner configuration.
Variation of ultimate load intensity with normalized (a) depth of confiner at D/B = 1.0 (b) top surface dimension of confiner at d/B = 2.0 for footing with confiner configuration.

Figure 9

(a) Variation of bearing capacity ratio with spacing (b) variation of settlement reduction factor with spacing, at confiner dimension (D/B = 2.0; d/B = 2.0).
(a) Variation of bearing capacity ratio with spacing (b) variation of settlement reduction factor with spacing, at confiner dimension (D/B = 2.0; d/B = 2.0).

Properties of sand.

Material (sand) Value
Classification of sand As per ISSCS (Indian Standard Soil Classification SP
Specific gravity 2.64
Coefficient of curvature(Cc) 1.13
Uniformity coefficient(Cu) 2.62
Maximum void ratio(emax) 0.87
Minimum void ratio(emin) 0.55
Natural void ratio(enatural) 0.68
Maximum dry unit weight (kN/m3) 16.46
Minimum dry unit weight (kN/m3) 13.62
Natural dry unit weight (kN/m3) 15.24
Angle of shearing resistance (¢) (Direct Shear Test) 32.6°
Relative Density 50%

Ultimate load intensity for different footing configurations under centric inclined loading.

Footing configuration Confiner dimension Horizontal reinforcement Spacing (Y) Load intensity (kN/m2) (i=5°) Load intensity (kN/m2) (i=10°) Load intensity (kN/m2) (i=20°)
Surface footing 35.45 34.19 31.80
D/B = 1.0; d/B = 1.0 50.06 47.98 33.77
D/B = 1.0; d/B = 1.5 59.55 53.04 34.94
Footing with confiner D/B = 1.0; d/B = 2.0 67.02 57.42 35.18
D/B = 1.5; d/B = 1.0 48.91 46.52 32.81
D/B = 1.5; d/B = 1.5 53.45 48.59 33.71
D/B = 1.5; d/B = 2.0 57.1 50.81 34.49
D/B = 2.0; d/B = 1.0 46.43 44.25 30.56
D/B = 2.0 ; d/B = 1.5 48.61 46.49 30.87
D/B = 2.0; d/B = 2.0 50.42 47.28 31.15
Footing with confiner and horizontal reinforcement D/B = 1.0; d/B = 1.0 0.25B 79.93 69.64 59.47
0.5B 73.13 62.94 54.29
0.75B 62.56 50.83 45.59
1B 55.55 48.49 42.49
D/B = 1.0; d/B = 1.5 0.25B 101.74 83.16 76.10
0.5B 90.5 80.28 71.39
0.75B 84.37 66.57 57.39
1B 70.9 60.45 50.09
D/B = 1.0; d/B = 2.0 0.25B 105.96 91.54 84.89
0.5B 90.5 85.12 78.49
0.75B 85.78 77.34 69.69
1B 78.43 64.82 51.29
D/B = 1.5; d/B = 1.0 0.25B 120.20 102.30 83.42
0.5B 96.21 89.0 73.4
0.75B 82.13 76.39 59.55
1B 61.10 59.40 53.64
D/B = 1.5; d/B = 1.5 0.25B 171.10 146.44 102.47
0.5B 110.0 94.42 77.89
0.75B 82.51 80 69.47
1B 62.80 61.76 54.31
D/B = 1.5; d/B = 2.0 0.25B 213.91 195.31 127.29
0.5B 138.75 118.91 98.01
0.75B 85.52 82.6 73.67
1B 62.80 65 60.91
D/B = 2.0; d/B = 1.0 0.25B 136.0 110.53 102.44
0.5B 102.91 91.71 86.11
0.75B 87.22 84.23 74.23
1B 75.54 73.4 57.89
D/B = 2.0; d/B = 1.5 0.25B 177.62 146.0 114.9
0.5B 123.8 100.5 92.9
0.75B 91.1 85.12 76.38
1B 80.0 75.23 66.41
D/B = 2.0; d/B = 2.0 0.25B 228.22 188.57 134.39
0.5B 151.10 143.72 102.2
0.75B 111.21 102.66 86.14
1B 90.0 81.4 69.47

Comparison of SRF for different footing configurations under centric inclined loading.

Footing configuration Confiner dimension Horizontal reinforcement Spacing (Y) SRF (i=5°) SRF (i=10°) SRF (i=20°)
Surface footing
Footing with confiner D/B = 1.0; d/B = 1.0 0.47 0.43 0.10
D/B = 1.0; d/B = 1.5 0.54 0.48 0.14
D/B = 1.0; d/B = 2.0 0.57 0.52 0.18
D/B = 1.5; d/B = 1.0 0.41 0.36 0.06
D/B = 1.5; d/B = 1.5 0.43 0.40 0.08
D/B = 1.5; d/B = 2.0 0.46 0.50 0.10
D/B = 2.0; d/B = 1.0 0.36 0.35 0.003
D/B = 2.0 ; d/B = 1.5 0.41 0.39 0.01
D/B = 2.0; d/B = 2.0 0.43 0.44 0.02
Footing with confiner and horizontal reinforcement D/B = 1.0; d/B = 1.0 0.25B 0.67 0.63 0.60
0.5B 0.54 0.53 0.52
0.75B 0.44 0.43 0.37
1B 0.39 0.36 0.31
D/B = 1.0; d/B = 1.5 0.25B 0.74 0.64 0.65
0.5B 0.70 0.60 0.63
0.75B 0.62 0.50 0.49
1B 0.53 0.42 0.41
D/B = 1.0; d/B = 2.0 0.25B 0.86 0.84 0.78
0.5B 0.71 0.65 0.64
0.75B 0.63 0.58 0.58
1B 0.54 0.46 0.43
D/B = 1.5; d/B = 1.0 0.25B 0.80 0.73 0.68
0.5B 0.66 0.64 0.59
0.75B 0.56 0.54 0.52
1B 0.45 0.35 0.41
D/B = 1.5; d/B = 1.5 0.25B 0.89 0.85 0.73
0.5B 0.78 0.70 0.66
0.75B 0.64 0.58 0.55
1B 0.51 0.46 0.43
D/B = 1.5; d/B = 2.0 0.25B 0.90 0.86 0.79
0.5B 0.77 0.73 0.69
0.75B 0.64 0.59 0.55
1B 0.59 0.43 0.42
D/B = 2.0; d/B = 1.0 0.25B 0.80 0.79 0.79
0.5B 0.71 0.71 0.69
0.75B 0.66 0.64 0.57
1B 0.61 0.55 0.49
D/B = 2.0; d/B = 1.5 0.25B 0.89 0.83 0.78
0.5B 0.77 0.77 0.72
0.75B 0.69 0.68 0.64
1B 0.62 0.59 0.51
D/B = 2.0; d/B = 2.0 0.25B 0.90 0.88 0.80
0.5B 0.85 0.80 0.76
0.75B 0.72 0.71 0.65
1B 0.60 0.59 0.52

Details of laboratory model tests,

Test series Foundation configuration Test parameters Number of tests
Variable Constant
A Only footing (surface footing) i=0,5°,10°,20° 4
B Footing with confiner d/B=1,1.5,2i= 5°,10°,20° D/B=1.0 9
d/B=1,1.5,2 D/B=1.5 9
i= 5°,10°,20°d/B=1,1.5,2i= 5°,10°,20° D/B=2.0 9
C Footing with confiner and reinforcement d/B=1,1.5,2; N=1–8Y/B=0.25,0.5,0.75,1i=5°10°20° D/B=1.0,L/B=1, y/B=0.1B 36
d/B=1,1.5,2; N=1–8Y/B=0.25,0.5,0.75,1i=5°,10°,20° d/B=1,1.5,2; D/B=1.5,L/B=1.5, y/B=0.1B 36
N=1–8Y/B=0.25,0.5,0.75,1i=5°,10°,20° D/B=2.0,L/B=2.0, y/B=0.1B 36

Comparison of BCRs for different footing configurations under centric inclined loading.

Footing zonfiguration Confiner dimension Horizontal reinforcement Spacing (Y) BCR (i=5°) BCR (i=10°) BCR (i=20°)
Surface footing
Footing with confiner D/B = 1.0; d/B = 1.0 1.41 1.4 1.10
D/B = 1.0; d/B = 1.5 1.67 1.55 1.14
D/B = 1.0; d/B = 2.0 1.89 1.67 1.15
D/B = 1.5; d/B = 1.0 1.37 1.36 1.07
D/B = 1.5; d/B = 1.5 1.5 1.42 1.1
D/B = 1.5; d/B = 2.0 1.61 1.48 1.13
D/B = 2.0; d/B = 1.0 1.3 1.29 1.0
D/B = 2.0 ; d/B = 1.5 1.37 1.35 1.01
D/B = 2.0; d/B = 2.0 1.42 1.38 1.02
Footing with confiner and horizontal reinforcement D/B = 1.0; d/B = 1.0 0.25B 2.25 2.04 1.95
0.5B 2.06 1.84 1.73
0.75B 1.76 1.48 1.49
1B 1.56 1.41 1.39
D/B = 1.0; d/B = 1.5 0.25B 2.87 2.43 2.5
0.5B 2.55 2.35 2.34
0.75B 2.38 1.95 1.88
1B 2.00 1.77 1.64
D/B = 1.0; d/B = 2.0 0.25B 3.00 2.68 2.78
0.5B 2.55 2.49 2.57
0.75B 2.42 2.26 2.28
1B 2.21 1.90 1.68
D/B = 1.5; d/B = 1.0 0.25B 3.39 3.0 2.74
0.5B 2.71 2.61 2.41
0.75B 2.31 2.23 1.95
1B 1.72 1.73 1.76
D/B = 1.5; d/B = 1.5 0.25B 4.82 4.29 3.36
0.5B 3.1 2.76 2.55
0.75B 2.32 2.33 2.28
1B 1.77 1.8 1.78
D/B = 1.5; d/B = 2.0 0.25B 6.03 5.71 4.18
0.5B 3.91 3.47 3.21
0.75B 2.41 2.41 2.42
1B 1.91 1.9 2.0
D/B = 2.0; d/B = 1.0 0.25B 3.83 3.23 3.36
0.5B 2.9 2.68 2.82
0.75B 2.45 2.46 2.43
1B 2.12 2.14 1.9
D/B = 2.0; d/B = 1.5 0.25B 5.0 4.27 3.77
0.5B 3.49 2.93 3.05
0.75B 2.56 2.48 2.5
1B 2.25 2.19 2.18
D/B = 2.0; d/B = 2.0 0.25B 6.43 5.51 4.41
0.5B 4.25 4.2 3.35
0.75B 3.13 3.0 2.82
1B 2.54 2.38 2.28
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