Transcript LOAD-CARRYING CAPACITY

Micropiles – UK Trends
Mike Turner
Applied Geotechnical Engineering
Increasing load capacity

1970s & 80s : 200-300 kN (compression)
[500 kN achievable]

End 1980s : 500-600 kN common

End 1990s : 1000-2000 kN
Diameters are also increasing

500kN : 125-160mm

1000kN : 190mm (typical)

2000kN: 240mm
- For rock-socketed micropiles
Increasing load and diameter
Micropiles: Pile load vs Pile Diameter
300
Pile socket diameter (mm)
250
200
150
100
50
0
0
500
1000
1500
Pile working load (kN)
2000
2500
Diameters are also increasing
for micropiles in soils

Because small rigs are more
powerful

450mm diameter piles not
uncommon with Klemm and
Hutte-type rigs

Blurring divisions between ‘piles’
and ‘micropiles’
Contiguous micropiled retaining walls
Increasing use, for:

Restricted sites: basements and citycentre redevelopments

Using 140-220mm thick-walled steel
tubes

Supported by ground anchors or props
Long slender micropiles

High slenderness ratios (length to
diameter)

100:1 not uncommon

200:1 installed and load-tested

33 metres long
Long slender micropiles –
working load and slenderness ratio
Long Piles - Working load vs Aspect Ratio
250
As pe ct Ratio
200
150
100
50
0
0
100
200
300
400
500
Working load (kN)
600
700
800
900
1000
Long slender micropiles – typical
working loads and pile lengths
Long piles - Working Load vs Pile Length
1000
900
800
Working load (kN)
700
600
500
400
300
200
100
0
0
5
10
15
Pile length (m)
20
25
30
35
Driven pipe piles

G-piles in Sweden (& Northern Europe?)

Dywidag-Systems just introduced systen
into UK

Driven ductile cast-iron pipe piles (Type
TRM): 500-1100kN capacity 119-170mm
OD
Chance-type piles

Mechanical auger piles, based upon the
Chance design

Very useful on railway infrastructure and
mobile phone tower installations

‘Screwfast’ piles
Ischebeck-type piles

‘Self-drilling’ piles and nails

Paul Woodfield has more details
Dynamic load testing

As an addition to static load testing

Mike Turner has more details