Credit Valley HospitalPre-loaded Micropiles for Vertical

Expansion of Parking Garage

SMART Contractometer Results

Nadir Ansari, Isherwood Associates Jim Bruce, Geo-Foundations Contractors Inc.

92 micropiles – 60 caisson augmentation; 32 grade beam t / c

Socket begins below existing 1070 diameter drilled shafts

967 lineal metres of drilling

300 kPa design adhesion in till

197mm diameter boring

Solid bar, #14, #18, #20 gr 75

Lightest service load = 688kN (c); 450kN (t)

Heaviest service load = 1200kN (c)

Credit Valley Hospital

Depth (m)

Soil Description N – Values Water Content

1

CLAYEY SILT TILL:Hard reddish brown to brown moist clayey silt; trace to some sand and

fine gravel

13%

2 3745

15%15%

346 18%

4 65 12%

5 78 15%

6 SILT: Very dense brown silt; trace sand

and fine gravel, seams of fine sandy silt and fine sand

15%

7 69 15%

Soil Description

Maximum Added Load Minimum Added Load

Item Owner Value Scheme

Pile Caps – lg 6m x 6m x 2.4 2.8 x 2.8 x 1.5

Pile Caps – sm 4.2 x 4.2 x 1.8 2.6 x 2.6 x 1.2

Pile Caps – all > 600 m3 120 m3

Caisson Piles 128 60Gr Beam Piles 64 32

Test Pile Specifications and Results

Maximum Applied Load 1791 kNShaft Diameter 197 mmArea of #20 bar 3168 mm2

Yield load of bar 1637 kNFree Length of Micropile 2.5 mAnchor Length of Micropile 4.0 m

Strength of Grout 52 MPa

Elastic Compression (max) 3.3 mmUltimate Soil Adhesion ± 720 kPa

200

400

600

800

1000

1200

1400

1600

1800

2000

-2 3 8 13 18 23 28 33 38 43

MOVEMENT (mm)

LOA

D (k

N)

Averageof Dialgauge 1and 2

Slope 2

Slope 1

Note: Slope 1 refers to calculated elongation from 80% of the free length. Slope 2 refers to calculated elongation from the free length plus 50% of anchor length of micropile. This elongations take into account the strength of steel and grout.

197 kPa

296 kPa

395 kPa

493 kPa

592 kPa

658 kPa

724 kPa

Creep Plot

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.0

1 10 100 1000Time (min)

Cre

ep (m

m)

977 kN

1mmpercycle2 mmpercycle1221kN

1465kN

1628kN

1791kN

3 mmpercycle4.5 mmpercycle

Contractometer Anchor Locations

AnchorPosition

(m)

0

1.083

2.167

3.250

4.333

5.417

6.390

FixedTop of Pile Movement

Movement Plot

-60-55-50-45-40-35-30-25-20-15-10-50

11-Jul 10-Aug 9-Sep 9-Oct 8-Nov 8-Dec 7-Jan 6-Feb 7-Mar 6-Apr 6-May 5-Jun 5-Jul

Time

MO

VE

ME

NT

(mm

)

-4000-3500-3000-2500-2000-1500-1000-5000500100015002000 L

oad

(kN

)

6.39 5.42 4.33 3.25 2.17 1.08 Dial Gauge Reading 0.00 Load

Movement Plot

-60-55-50-45-40-35-30-25-20-15-10-50

11-Jul 10-Aug 9-Sep 9-Oct 8-Nov 8-Dec 7-Jan 6-Feb 7-Mar 6-Apr 6-May 5-Jun 5-Jul

Time

MO

VE

ME

NT

(mm

)

-4000-3500-3000-2500-2000-1500-1000-5000500100015002000

Loa

d (k

N)

6.39 5.42 4.33 3.25 2.17 1.08 Dial Gauge Reading Load

Movement along the Micropile at Design Load of 1200 kN

0

510

1520

2530

35

6.39 5.42 4.33 3.25 2.17 1.08 0.00Depth along the Micropile (m)

Mov

emen

t (m

m)

topbottom

Movement Along Test Pile at 1200kN

Movement along the Micropile at 1628 kN

05

101520253035

6.39 5.42 4.33 3.25 2.17 1.08 0.00Depth along the Micropile (m)

Mov

emen

t (m

m)

topbottom

Movement along the Micropile at failure load 1791 kN

05

10152025303540

6.39 5.42 4.33 3.25 2.17 1.08 0.00Depth along the Micropile (m)

Mov

emen

t (m

m)

topbottom

Tensile Stress Distribution Pattern Under Preloading

Compressive Stress Distribution Pattern Under Failure loads

Distribution Pattern of the First Principal Stress around Pile Top