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 Computer Program DFSAP Deep Foundation System Analysis Program Based on Strain Wedge Method

PILE CAP EFFECT AND PILE DEFLECTION PATTERNS IN THE PROGRAM DFSAP

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

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

P2P2 K 22 K 11 K 66 P1P1 M3M3 Y Y XX P2P2 K 22 K 33 K 44 P3P3 M1M1 Y Y ZZ A) Loading in the Longitudinal Direction (Axis 1 or X Axis ) B) Loading in the Transversal Direction (Axis 3 or Z Axis ) Single Shaft

Pile Cap T v PoPo o MoMo PvPv y K face KVKV KHKH Piles/Shafts

Loading Direction

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

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

Type of Shaft Analysis vs. Shaft Response

T PoPo MoMo PvPv y 65 ft 6 ft P v = 100 kip P o = 150 kip M o = 800 kip-ft L/T = 2.5 Intermediate Shaft Soil Profile – S5 Short Shaft Analysis Intermediate Analysis

T PoPo MoMo PvPv y 75 ft 6 ft P v = 100 kip P o = 150 kip M o = 800 kip-ft L/T = 3.1 Intermediate Shaft Soil Profile – S5 Short Shaft Analysis Intermediate Analysis Short Shaft Analysis Intermediate Analysis

T PoPo MoMo PvPv y 90 ft 6 ft P v = 100 kip P o = 150 kip M o = 800 kip-ft L/T = 4.0 Long Shaft Soil Profile – S5 Short Shaft Analysis Long Shaft Analysis

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

T PoPo MoMo PvPv y 55 ft 6 ft P v = 100 kip P o = 800 kip M o = 3000 kip-ft M EQ = 6.0 Soil Profile – S7 Liquefaction DFSAP

T PoPo MoMo PvPv y 65 ft 6 ft P v = 100 kip P o = 800 kip M o = 3000 kip-ft M EQ = 6.0 Soil Profile – S7 Liquefaction DFSAP

T PoPo o MoMo PvPv y 90 ft 6 ft P v = 100 kip P o = 800 kip M o = 3000 kip-ft M EQ = 6.0 Soil Profile – S7 Liquefaction DFSAP

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

T PoPo MoMo PvPv y L 6 ft Soil Profile – S5 1 Shaft-Length Effect on the p-y Curve P-y Curve at 5 ft depth P-y Curve at 20 ft depth

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

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.