Plate Load Test

Site Investigation and In situ testing

Initial Soil Conditions
INDICES Origin Geologic Age Grain Sizes Mineralogy Plasticity Shape Sphericity Roundness Angularity Void ratio limits
(emax and emin)
Zw Z

STATE Void Ratio, e0 Unit Weight, γs Relative Density, DR Vertical Stress, σvo Hydrostatic, uo Saturation, Sr Geostatic K0 = σho’/σvo’ Stiffness, G0 = Gmax Cementation Fabric, void indexIvo Intact or Fissured

Soil Element A

Soil Parameters and Properties
CONDUCTIVITY
Hydraulic: kv, kh Thermal: ke Electrical: Ω, ζ Chemical: Df

STIFFNESS
Stiffness: G0 = Gmax Shear Modulus, G Bulk Modulus, K’ Poisson’s Ratio, ν Effects of Anisotropy Nonlinearity

COMPRESSIBILITY
Recompression, Cr Preconsolidation, σvy’ Consolidation, cv Virgin Compression, Cc Swelling index, CsSTRENGTH
Drained and Undrained Peak (su, c’, φ’) Post-peak Remoulded/Softened/CS Residual Cyclic Behaviour

RHEOLOGICAL
Creep, Cα Strain rate, δε/δt Age (t)

Site Characterisation Methods
•

Drilling & Sampling
• •

Soil Borings Rock Coring Standard Penetration (SPT) Cone Penetration (CPT + CPTu) Flat Plate Dilatometer (DMT) Pressuremeter (PMT) Vane Shear (VST) Mechanical Waves (P-, S-,R-waves) Electromagnetic (radar, resistivity, dielectric)

•

In Situ Tests
• • • • •

•

Geophysical Methods
• •

Sampling & Lab Testing of Clays and Silts

φ’

High-Quality Sampling

OCR

Some In Situ Tests

Standard Penetration Test (SPT)
SPT hammer
Anvil

63.5-kg Drop Hammer Repeatedly Falling 0.76 m

63.5 kg mass

Count number of blows to drive sampler frompenetration of 150 to 450 mm

760 mm

Split-Barrel (Drive) Sampler: O.D. = 50 mm I.D. = 35 mm L = 760 mm

Corrections are normally applied to the SPT blow count to account for differences in: • energy imparted during the test • the stress level at the test depth

SPT (unchanged since 1902 !)

SPT split spoon
Measured N-value (blows/foot)

Cone Penetration Test (CPT)

35.7 mmdiameter = 1000 mm2 area pushed in at 20 mm/s

CPT Setup

Smaller CPT Trucks (anchors/dead-weight)

Cones: Pore Pressure and Resistivity Measurement
Pore pressure transducer on face of cone

Various types of cones with pore pressure transducers

Resistivity module

Various types of cones with pore pressure transducers and additional resistivity module

CPT Results

0 5
Depth (m)10 15 20 25 30

Piezocone Test (CPTU)

CPT/CPTU Interpretation - Soil Type

Revised classification Chart
Q= [(qc – σv0)/pref ] [ pref /σ’v0]n F = fs/ (qc – σvo)

n = fn. (Q, F)

Typical CPTU data in Perth CBD (Site A)
qcnet (MPa) 0 0 10 20 30 0 0 1 Fr (%) 2 3 4 5 -200 0 0 u2 (kPa) 200 400 600 -0.2 0 Bq 0 0.2

2

2

2

2

4

4

4

4____________________________________________________________

________
6 6 6 6

Depth (m)

____________________________________________________________

________
10 10 10 10

8

8

8

8

12

12

12

12

14 14 14 14 ____________________________________________________________

________ 16 16 16 16

18

18

18 u0

18

20

20

20

20

Classification (3 layers at Site A)
1000 10007 8&9 7

100 Q = qcnet / 'v0

6 5
Q = qcnet / 'v0

100

6

5
10

4
10

Upper sand:2-5.5m 3 Upper clay: 6-9m 1 Lower clay:15-18m 2

4 3 2
0 0.1 0.2 0.3 0.4

1 0.1 1 Fr (%) 10

1 -0.1

Bq = Δu2/qcnet

“Upper clay” : Sandy silt ; “Lower clay”: Clayey silt

SCPTU profiles
Tip Resistance Sleeve Friction Porewater Pressure Friction Ratio Shear Wave Velocity

qT(MPa)
0 0 5 10 15 0

fs (kPa)
200 400 600 0

u2 (kPa)
500 1000 1500 0 2

FR (%)
4 6 8 10 0 100

Vs (m/s)
200 300 400 500

5

10

Depth (m)

15

20

25

30

Cone Details

Soil Stiffness
τ τmax Typical shear behaviour
0.5τmax G50 Gmax

γ
3000

Typical strain ranges

2000 Eu/su 1000

Retaining walls Foundations

0 0.001

0.01

0.1 Axial strain (%)

1...