BEHAVIOUR of PILES under the effect of

loading in SANDY SOIL

By-

PILE FOUNDATIONS

Bearing Capacity

Bearing capacity is the capacity of soil to support the loads applied to the ground. The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil.

Pile foundations are used when the bearing capacity of the soil is low, and the load applied on the foundation is comparatively very high.

Function of piles:As with other types of foundations, the purpose of a pile foundation is:1.) To transmit a foundation load to a solid ground.2.) To resist vertical, lateral and uplift load.

What is pile?Piles are structural members that are made of steel, timbre, concrete, etc.

When is it adopted?Pile-foundation is adopted when loose soil is extended to a great depth.The load of the super-structure is transmitted by the pile to the hard stratum below or it is resisted by the friction developed on the sides of the piles.

• Metal Box arrangement :-The box is filled with sand in layers of certain thickness.After one layer is filled, it is compacted to get the required height which was calculated taking in consideration the required density of the sand.

• Deflectometer arrangement :-The deflectometer is placed behind the pile cap.

Experimental Setup

The needle is first pressed in and then the magnetic base isattached to a sheet metal box placed on the soil layer.The least count of deflectometer is 0.01 mm.

• Pile :-PVC pipe is used as the pile material.After the sand has been filled and the required density hasbeen achieved, the pile is driven in the soil with the help of ahammer.The hammer should be dropped such that no damage is doneto the pile.

• Pile Cap :-The Pile Cap is fabricated from a wooden block of 10mm thickness generally.It is square in shape.A circular hole is cut out in its centre to allow the pile to fit.A hole is drilled at one of its side for attaching the hook where load can be applied.

Use of LPILE software:-

LPILE is a special purpose program based onrational procedure for analyzing a pile underlateral loading using the p-y method.

The program computes deflection, bendingmoment, shear force and soil response overthe length of the pile.

As an option, LPILE provides graphs of pile-head deflections for various pile lengths tohelp with optimum pile penetrations.

Model Dimensions :-General :-• Relative density of Sand = 10 ( Loose Sand)• Friction angle of loose soil = 32.5• P-y modulus of loose sand = 6750 kN/m3• Effective unit weight (sand) = 16 kN/m3• Length (L) of pile = 800 mm• Length of pile below ground level = 640mm• Outlet diameter of model pile = 32 mm• Inlet diameter of model pile = 26.8 mm• Modulus of Elasticity of model pile = 2225 kPa• Pile Cap material = Wood

Time(min)

Load Deflection (mm)

0 Hanger 0.48

5 “ 0.50

25 “ 0.50

30 “ 0.50

31 “ + 0.5 1.93

35 “ 1.96

40 “ 1.98

45 “ 2

55 “ 2.01

60 “ 2.01

61 “ + 0.5 3.76

65 “ 3.84

75 “ 3.88

80 “ 3.90

85 “ 3.91

Time (min) Load Deflection (mm)

90 “ 3.92

91 “ + 0.5 6

95 “ 6.09

100 “ 6.12

105 “ 6.15

120 “ 6.19

121 “ + 0.5 9.05

125 “ 9.14

130 “ 9.20

137 “ 9.26

145 “ 9.30

150 “ 9.31

151 “ + 0.5 11.38

155 “ 11.46

160 “ 11.53

Time (min) Load Deflection (mm)

165 “ 11.59

172 “ 11.63

180 “ 11.68

181 “ + 0.5 14.05

185 “ 14.21

190 “ 14.31

197 “ 14.40

203 “ 14.45

210 “ 14.50

211 “ + 0.5 16.65

220 “ 17.01

230 “ 17.15

240 “ 17.25

P-y Curve

Pile-head Deflection vs. Load

Bending Moment vs. Depth

Lateral Deflection vs. Depth

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