Analysis of Laterally Loaded Drilled Shafts and Piles Using Lpile
Analysis of Laterally Loaded Drilled Shafts and Piles Using Lpile
Analysis of Laterally Loaded Drilled Shafts and Piles Using Lpile
Shin-Tower Wang, Ph.D., P.E. Ensoft, Inc./Lymon C. Reese & Associates Austin, Texas
April 3, 2009
Outlines
Numerical solution for soil-structure interaction Characteristic Shape of p-y Curves Available p-y Curve Criteria Common Input Values
Special consideration for large-diameter piers Effect of nonlinear EI on deflection Special features in LPILE
Methods of Solution
Linearly elastic solution (Poulos and Davis, 1980) emphasizes the condition of continuity although the soil cannot be characterized as a linearly elastic material. Limit-equilibrium solution (Broms, 1965) finds the ultimate lateral load at failure, but soil-structure interaction at lesser loads is not addressed. The p-y method with beam-column model (McClelland, Matlock, Reese, 1958-1975) has been developed extensively to take into account the soil-structure interaction and nonlinear resistance of soils. 3-D Finite-Element method
Plane-Strain Failure
Differential Equation
d y d y EI 4 Px 2 E py y W 0 dx dx
EI y x Px Epy W = pile stiffness = pile deflection = distance along pile = axial load on pile and = slope of secant to p-y curve at point on pile = distributed lateral loading
c. a. b. b. c. Initial Linear-elastic section Transition from linear to nonlinear section Yield section into limit state or plasticity failure
a.
Soft Clay (Matlock, 1970) Stiff Clay (1). with free water (Reese et al., 1975) (2). Without free water (Reese & Welch, 1975) Sand (Reese model & API Model) Liquefied Sand (Rollins et al., 2005) c-f Soil (Evans and Duncan*, 1982) Strong Rock (Reese & Nyman, 1978) Weak Rock (Reese, 1997)
Soil Stiffness, e50 Initial Stiffness of p-y Curve, k Rock Properties, RQD, qu, etc.
Soft Clay
Static Loading
Cyclic Loading
Static Loading
Cyclic Loading
Static Loading
Cyclic Loading
k yk ks
pk
ym
u pu yu
y
b/60 3b/80
Use of this p-y curve is not recommended without a load test to establish k
Vuggy Limestone
p
Perform proof test if deflection is in this range
pu = b su
Es = 100su
Es = 2000su
NOT TO SCALE
y 0.0004b 0.0024b
Weak Rock
p Kir pur
ya
Required rock properties Uniaxial Compressive Strength, su (from lab tests) RQD (from field investigation records) Rock Mass Modulus (interpreted) krm (from lab tests or estimated) y Effective Unit Weight (from lab tests)
Mt Pt
Layer 1 Layer 2 Pile Length Distance to Ground Surface
Layer 3
Note: Origin of Coordinate System for Pile and Soil Layers is Located at the Pile Head
yt
Layer 1 Layer 2
Pile Length
Layer 3
Note: Origin of Coordinate System for Pile and Soil Layers is Located at the Pile Head
B H
0.2 Tip rotation bearing, Fb (need large mobilization) Fb Contact friction, Fs 0.05B
Size Effect
1.
For linear elastic portion of the p-y curves the size effect is not significant on initial k values. For ultimate soil resistance Pu is a function of the pile diameter.
2.
3.
Most correlation coefficients in current p-y criteria were derived based on pile diameter of 2 ft to 4 ft.
Uncrack/Crack EIs
Adjust the Passive Earth Pressure Not Over The Bending Capacity
Concrete Properties
Thank You