Faculty of Civil and Geodetic EngineeringUniversity of Ljubljana

Axial compression behaviour of driven steel piles in soft marine soils of the Port of Koper

Sebastjan Kuder

18th European Young Geotechnical Engineers Conference, Ancona, Italy, 2007.

Introduction

Source: Google Earth

History

Source: www luka kp si

Geological conditions

γ = 20 – 21 kN/m3 ϕ’=35°, c’=0

γ = 17,0 – 18,5 kN/m3 cu = 10 kPa (at 0m) to 25 kPa (at -10 m) ϕ’=20°, c’=0

Eoed = 2,0 – 2,5 MPa pLM = 350 – 480 kPa (pressuremeter) EM = 1,3 – 2,0 MPa (pressuremeter)

AC class.: CL, CH, OH w = 33,2 – 47,2 % Ic = 0,15 – 0,55 γ = 15,8 – 18,1 kN/m3 cu = 20 – 55 kPa (DMT, CPT) ϕ’ = 15 – 20°, c’ = 0 – 7 kPa (laboratory)

Eoed = 1,4 – 2,5 MPa (at -10 m) Eoed = 2,5 – 3,5 MPa (at -30 m) k = 1 x 10-10 m/sec (CPT) pLM = 500 – 1000 kPa (pressuremeter) EM = 1,0 – 3,6 MPa (pressuremeter)

AC class.: GP, GM, GC, SM, SC, SU, ML γ = 20 – 22 kN/m3 ϕ’ = 28 – 40° (SPT)

Eoed = 25 – 60 MPa pLM = 1000 – 2500 kPa (pressuremeter) EM = 15 – 26 MPa (pressuremeter)

AC class.: CL w = 18,8 – 20,5 % Ic = 1,04 – 1,06 γ = 20,9 – 21,0 kN/m3

cu = 105 – 120 kPa (laboratory) Eoed = 13,6 – 16,2 MPa (400 – 800 kPa) Eoed = 42 – 56 MPa (800 – 1600 kPa) k = 1 x 10-11 – 2 x 10-11 m/s

Pile foundations

Pile foundations

Pile foundations

Objectives of the study

• To analyze existing data, • to design a model which would enable the

prediction of pile behaviour,• to compare the results of different

methods.

Analysis of existing data

• 17 static load tests• 2 dynamic load tests• Borehole logs• Pile driving logs• Pressuremeter test

results• Laboratory tests

results• Flat dilatometer test

results

Numerical model

Numerical model – cont.

• Shaft: rsi =rsi (s, Esi , qsi , B), for each segment

• Base rb =rb (b, Eb , qb , B),• Initial estimate based on

borehole logs, pile driving logs, laboratory tests.

Results

Soil layer

Average depth qs Es

m kPa MPaEMB 0-4 10 2S1 5 10 2CS1 8 15 3CS1 20 30 6CS2 29 45 9CS3 40 60 18GFc1 30 50 10GFc2 34 60-70 12-14GFc2 42 65-80 13-16GFc3 44 90 18

PilePile

lengthType of

base qb Eb

m kPa MPa13 42.4 cone 5500 5519 45.4 hollow 3000 30P3 41 hollow 4600 46vez7c 44 cone 7800 78

Shaft

Base

Results

Soil layer

Average depth qs Es

m kPa MPaEMB 0-4 10 2S1 5 10 2CS1 8 15 3CS1 20 30 6CS2 29 45 9CS3 40 60 18GFc1 30 50 10GFc2 34 60-70 12-14GFc2 42 65-80 13-16GFc3 44 90 18

PilePile

lengthType of

base qb Eb

m kPa MPa13 42.4 cone 5500 5519 45.4 hollow 3000 30P3 41 hollow 4600 46vez7c 44 cone 7800 78

Shaft

Base

Results

Soil layer

Average depth qs Es

m kPa MPaEMB 0-4 10 2S1 5 10 2CS1 8 15 3CS1 20 30 6CS2 29 45 9CS3 40 60 18GFc1 30 50 10GFc2 34 60-70 12-14GFc2 42 65-80 13-16GFc3 44 90 18

PilePile

lengthType of

base qb Eb

m kPa MPa13 42.4 cone 5500 5519 45.4 hollow 3000 30P3 41 hollow 4600 46vez7c 44 cone 7800 78

Shaft

Base

Results

Soil layer

Average depth qs Es

m kPa MPaEMB 0-4 10 2S1 5 10 2CS1 8 15 3CS1 20 30 6CS2 29 45 9CS3 40 60 18GFc1 30 50 10GFc2 34 60-70 12-14GFc2 42 65-80 13-16GFc3 44 90 18

PilePile

lengthType of

base qb Eb

m kPa MPa13 42.4 cone 5500 5519 45.4 hollow 3000 30P3 41 hollow 4600 46vez7c 44 cone 7800 78

Shaft

Base

Comparison of methods

• Location of pile vez7c• Static load test• Dynamic load test• Pressuremeter method• Numerical prediction

Comparison of methods – cont.

0

1000

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3000

4000

5000

6000

7000

8000

9000

10000

0 20 40 60 80 100 120 140s [mm]

Q [k

N]

staticdynamicnumericalpressurem.

Conclusions

• Very comparable results from dynamic load tests and static load tests,

• in such conditions pressuremeter method can moderately underestimate shaft bearing capacity,

• numerical method gives good results with some minor discrepancies,

• more advanced model of skin friction should be considered,

• for the future: some test piles should be instrumented along their shafts,

• the numerical model will be adapted to conditions in another locations.