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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.

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Presentation on theme: "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."— Presentation transcript:

1 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

2 SOIL LIQUEFACTION AND LATERAL SPREADING OF SOIL

3 Current Available Procedures That Assess the Pile/Shaft Behavior in Liquefied Soils (Using the Traditional P-y Curve): 1.Construction of the p-y curve of soft clay based on the residual strength of liquefied sand presented by Seed and Harder (1990) 2.The use of random P mult < 1 to reduce the stiffness of the traditional p-y curve of sand 3.Reduce the unit weight of liquefied sand with the amount of R u (Earthquake effect in the free-field ) and then build the traditional p-y curve of sand based on the new value of the sand unit weight. (proposed by Brown based on Cooper River Test)

4 Fig. 1Corrected blowcount vs. residual strength (Seed and Harder, 1990)

5 Pile Deflection, y Soil-Pile Reaction, p Upper Limit of S r using soft clay p-y curve Lower Limit of S r API Procedure Corrected blowcount vs. residual strength, S r (Seed and Harder, 1990) Treasure Island Test Result (Rollins and Ashford) P-Y Curve of Completely Liquefied Soil 19

6 Post-liquefaction stress-strain behavior of completely liquefied sand ( u c = 3c and R u =1) Axial Strain, Deviator Stress, d Post-liquefaction stress-strain behavior of partially liquefied sand ( u c < 3c and. R u <1) xoxo d = 2 S r Fig. 1 Subsequent undrained stress-strain behavior of sand that has experienced partial or complete liquefaction

7 A B Fully Liquefied Soil (R u =1) Water Pressure in the Free- and Near-Field Due to the Earthquake Shaking and Equivalent Static Load from the Superstructure Partially Liquefied Soil (R u < 1)

8 Post-liquefaction undrained stress-strain behavior of completely liquefied Fraser sand R u = 1 R u = 0.88

9 Fig. 2 Effect of Cyclic Loading upon Subsequent Undrained Stress-Strain Relationship for Sacramento River Sand (Dr = 40%) (Seed 1979)

10 Validation Example for Pile and Pile Group in Liquefiable soil profile Treasure Island Test Report, Chapter 6

11 Peak Ground Acceleration (a max ) = 0.1 g Earthquake Magnitude = 6.5 Induced Porewater Pressure Ratio (r u ) = Soil Profile and Properties at the Treasure Island Test Soil-Pile Reaction, p Pile Deflection, y Treasure Island Test Result (Rollins and Ashford) Upper Limit of S r using soft clay p-y curve Lower Limit of S r API Procedure

12 TREASURE ISLAND TEST

13

14

15 Pile-Head Deflection, Yo, mm P i l e - H e a d L o a d, P o, k N CISS, 0.61 m EI = kN-m 2 Observed Predicted (SWM) Predicted (Com624) N o - L i q u e f a c t i o n Post-Liquefaction (u xs, ff + u xs, nf )

16 Pile-Head Response (Y o vs. P o ) for 0.61-m Diameter CISS at Treasure Island Test.

17 API (P mult = 0.3) p-y Curve at 1.5 m Below Ground (0.61-m Diameter CISS )

18 0.2 m Below Ground 1.5 m Below Ground 3.2 m Below Ground p-y Curve of 0.61-m Diameter CISS in Liquefied Soil. (Treasure Island, After Rollins et al )

19 p-y Curve Empirical Formula in Liquefied Sand by Rollins et al p (d=324 mm) = A(By) C for D r = 50% where: A = 3 x (z+1) 6.05,B = 2.8 (z+1) 0.11 C = 2.85(z+1) z is depth in (m) y is lateral deflection (mm) p multiplier = 3.81 ln d p = p (d=324 mm) x p multiplier

20 Pile-Head Response (Y o vs. P o ) for an Isolated m Diameter CISS at Treasure Island Test. Curve # 1 Curve # 2 Pile Load (kN) Deflection at Load Point (mm)

21 p-y Curve of m Diameter CISS in Liquefied Soil (Treasure Island)

22 Responses of Individual Piles in a 3 x 3 Pile Group in Non-Liquefied Soil Profile at the Treasure Island Test (Rollins et al. 2005a)

23 Pile-Head Response (Y g vs. P g ) for a 3 x 3 CISS Pile Group (0.324-m Diameter) at Treasure Island Test. (After Rollins et al. 2005) Deflection at Load Point (mm) Pile Load (kN) Curve # 1 Curve # 2 Curve # 1 Curve # 2

24 A B, C E p-y Curve of a 3 x 3 Pile Group in Liquefied Soil (Treasure Island, m CISS)

25 Lateral Soil Spread

26 Bartlett and Youd, 1995 (Current Practice) SOIL LATERAL SPREADING CHALLANGES: Mobilized Driving Lateral Forces Acting on Piles and Generated by Crust Layer(s) Varying Strength of Liquefied Soil(s) Amount of Soil Lateral Displacement Stress-Strain Behavior of Fully Liquefied Sand Axial Strain, Deviator Stress, d xoxo Soil Lateral Displacement (X o ) in DFSAP

27 (Ishihara)

28 Shaft Diameter Shaft Cross Section Liquefied Soil Soil Flow Around LATERAL SOIL SPREAD

29

30 Pile head load = 100 kN Pile head moment = 316 kN-m No-Liquefaction Liquefaction Liquefaction + Lateral Spread

31 Pile head load = 100 kN Pile head moment = 316 kN-m No-Liquefaction Liquefaction Liquefaction + Lateral Spread

32 Hokkaido Island Test (Ashford et al. 2006, ASCE J.) LATERAL SOIL SPREAD, TEST 1

33 Hokkaido Island Test (Ashford et al. 2006) LATERAL SOIL SPREAD Peak Ground Acceleration (a max ) = 0.4 g Earthquake Magnitude = 6.0 Induced Porewater Pressure Ratio (r u ) = 1.0

34 DFSAP m-Diameter Steel Pipe Pile Hokkaido Island Test (Ashford et al. 2006, ASCE J.) LATERAL SOIL SPREAD, ISOLATED FREE-HEAD PILE

35 DFSAP Hokkaido Island Test (Ashford et al. 2006, ASCE J.) LATERAL SOIL SPREAD, ISOLATED FREE-HEAD PILE

36 Rotation = 1 Deg. (Not fully fixed) Hokkaido Island Test (Ashford et al. 2006, ASCE J.) 2 X 2 FIXED-HEAD PILE GROUP WITH CAP DFSAP Steel Pipe Pile

37 Dense Sand Loose Sand Clay = 6 kN/m 3, Dr = 21-35% = 30 o, 50 = 0.01 = 7 kN/m 3, Dr = 69-83% = 36 o, 50 = Cu= 44 kPa = 16 kN/m Pile Cap Length (m) Pile Cap Width (m) Pile Cap Height (m) Pile Spacing (m) Wall Thick. (m) Diameter (m) Pile Length (m) UC Davis, Centrifuge Test (Brandenberg and Boulanger, 2004)

38

39 UC Davis, Centrifuge Test on 2 x 3 Fixed-Head Pile Group (After Brandenberg and Boulanger, 2004) Pile Displacement Bending Moment a max = 0.67 gMagnitude = 6.5

40 p-y Curves at Different Depths for a Lateral Soil Spreading Case (UC Davis Test, a max = 0.3g)

41 Input Data 1. Shaft/Pile Properties Shaft length and diameter Shaft-head location above ground Moment and axial load at shaft head Type of the shaft cross-section and material Uniaxial fc 28 of concrete Percentage of rebars Percentage of horizontal steel Thickness of steel shell (if any) F y of steel (nonlinear modeling)

42 Input Data (Continue) 2. Soil properties: Thickness of soil layer of soil layer Effective unit weight of soil ( ) Normal strain of sand at 50% strength, 50% Uniformity coefficient (C u ) Angle of internal friction, (Sand) Undrained shear strength, S u (Clay) Relative density (Dr) Percentage of fines (passing from sieve # 200) Sand grain roundness parameter ( ) 3. Earthquake Magnitude, M Peak ground acceleration, a max

43 QUESTIONS ????


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