Prepared by J. P. Singh & Associates in association with Mohamed Ashour, Ph.D., PE

Computer Program DFSAPDeep Foundation System Analysis ProgramBased on Strain Wedge Method • Prepared by • J. P. Singh & Associates • in association with • Mohamed Ashour, Ph.D., PE • West Virginia University Tech • and • Gary Norris Ph.D., PE • University of Nevada, Reno • APRIL 3/4, 2006

PILE CAP EFFECT AND PILE DEFLECTION PATTERNS IN THE PROGRAM DFSAP

FOUNDATION CUT-OFF SECTION FOUNDATION CUT-OFF SECTION SHAFT GROUP WITH CAP SINGLE SHAFT FOUNDATION (Z) (X) (X) (Z) Fig. 2-1 General Axis of Bridge and Bridge Foundations

Pile Passive Wedges Pile/Shaft Group with Cap y Cap Passive Wedge

Y Y P2 P2 M3 M1 K11 K33 P1 P3 K66 K44 K22 K22 Single Shaft X X Z Z Y Y A) Loading in the Longitudinal Direction (Axis 1 or X Axis ) B) Loading in the Transversal Direction (Axis 3 or Z Axis )

Pv Mo y Po o Pile Cap Kface KH T KV v Piles/Shafts

Loading Direction

Piles + Cap Piles + Cap Piles Piles Cap Cap 320 410 Free-Head Fixed-Head Effect of Pile-Head Conditions on Cap Resistance at the Same Deflection Value in DFSAP

Varying Deflection Patterns Based on Shaft Type Yo Yo Yo Linearized Deflection Linearized Deflection Deflection Pattern h = 0.69 Xo Xo > h > 0.69 Xo Xo h = Xo Xo  Deflection Pattern   Zero Crossing  Zero Crossing Zero Crossing Short Shaft L/T  2 Intermediate Shaft 4 > L/T > 2 Long Shaft L/T  4 L = SHAFT LENGTH T = (EI/f )0.2 f = Coefficient. of Modulus of Subgrade Reaction

Type of Shaft Analysis vs. Shaft Response

Short Shaft Analysis Intermediate Analysis Pv Mo y Po 65 ft 6 ft Soil Profile – S5 Pv = 100 kip Po = 150 kip Mo = 800 kip-ft L/T = 2.5 Intermediate Shaft T

Short Shaft Analysis Intermediate Analysis Short Shaft Analysis Intermediate Analysis Pv Mo y Po 75 ft 6 ft Pv = 100 kip Po = 150 kip Mo = 800 kip-ft L/T = 3.1 Intermediate Shaft Soil Profile – S5 T

Short Shaft Analysis Long Shaft Analysis Pv Mo y Po 90 ft 6 ft Soil Profile – S5 Pv = 100 kip Po = 150 kip Mo = 800 kip-ft L/T = 4.0 Long Shaft T

3x 3 Shaft Group with Cap 6-ft-diameter shafts

3 x 3 6-ft-Diameter Shaft Group/Cap in Soil Profile – S5

3 x 3 SHAFT GROUP IN SOIL PROFILE S-5 Shaft Length = 55 ft, Diameter = 6 ft

3 x 3 SHAFT GROUP OF 55-FT LENGTH AND 6-FT-THICK CAP IN SOIL PROFILE S-5

Soil Liquefaction on Shaft Response in DFSAP Program

Pv Mo y Po 55 ft 6 ft DFSAP Soil Profile – S7 Liquefaction Pv = 100 kip Po = 800 kip Mo = 3000 kip-ft MEQ = 6.0 T

Pv Mo y Po 65 ft 6 ft DFSAP Soil Profile – S7 Liquefaction Pv = 100 kip Po = 800 kip Mo = 3000 kip-ft MEQ = 6.0 T

Pv Mo y Po o 90 ft 6 ft Soil Profile – S7 Liquefaction DFSAP Pv = 100 kip Po = 800 kip Mo = 3000 kip-ft MEQ = 6.0 T

Effect of Shaft Length and Soil Layers on the p-y Curve at Certain Depth

P-y Curve at 5 ft depth P-y Curve at 20 ft depth Pv Mo y Po L 6 ft Soil Profile – S5 1 Shaft-Length Effect on the p-y Curve T

Pv Mo y Po 65 ft 6 ft Soil Profile – S7 Liquefaction 2 Effect of Soil Profile (Liquefaction) on the p-y Curve at the Same Depth. T

6-FT-DIAMETER SHAFT IN SOIL PROFILE – S7

Conclusions: • The pile cap should be analyzed as a part of the foundation system and is a affected by pile-head stiffness. • The deflection mechanism (short/intermediate/long) of pile governs the interaction between the pile and soil (i.e. pile stiffness) • The p-y curve at a particular depth is not unique and varies based on the type of pile/shaft (short/intermediate/long) • The p-y curve at a particular depth is affected by the changes of the properties of the overlying and underlying soil layers.

Prepared by J. P. Singh & Associates in association with Mohamed Ashour, Ph.D., PE