1. Micropiles – UK Trends Mike Turner Applied Geotechnical Engineering

2. Increasing load capacity 1970s & 80s : 200-300 kN (compression) 1970s & 80s : 200-300 kN (compression) [500 kN achievable] [500 kN achievable] End 1980s : 500-600 kN common End 1980s : 500-600 kN common End 1990s : 1000-2000 kN End 1990s : 1000-2000 kN

3. Diameters are also increasing 500kN : 125-160mm 500kN : 125-160mm 1000kN : 190mm (typical) 1000kN : 190mm (typical) 2000kN: 240mm 2000kN: 240mm - For rock-socketed micropiles - For rock-socketed micropiles

4. Increasing load and diameter

5. Diameters are also increasing for micropiles in soils Because small rigs are more powerful Because small rigs are more powerful 450mm diameter piles not uncommon with Klemm and Hutte-type rigs 450mm diameter piles not uncommon with Klemm and Hutte-type rigs Blurring divisions between ‘piles’ and ‘micropiles’ Blurring divisions between ‘piles’ and ‘micropiles’

6. Contiguous micropiled retaining walls Increasing use, for: Restricted sites: basements and city- centre redevelopments Restricted sites: basements and city- centre redevelopments Using 140-220mm thick-walled steel tubes Using 140-220mm thick-walled steel tubes Supported by ground anchors or props Supported by ground anchors or props

7. Long slender micropiles High slenderness ratios (length to diameter) High slenderness ratios (length to diameter) 100:1 not uncommon 100:1 not uncommon 200:1 installed and load-tested 200:1 installed and load-tested 33 metres long 33 metres long

8. Long slender micropiles – working load and slenderness ratio

9. Long slender micropiles – typical working loads and pile lengths

10. Driven pipe piles G-piles in Sweden (& Northern Europe?) G-piles in Sweden (& Northern Europe?) Dywidag-Systems just introduced systen into UK Dywidag-Systems just introduced systen into UK Driven ductile cast-iron pipe piles (Type TRM): 500-1100kN capacity 119-170mm OD Driven ductile cast-iron pipe piles (Type TRM): 500-1100kN capacity 119-170mm OD

11. Chance-type piles Mechanical auger piles, based upon the Chance design Mechanical auger piles, based upon the Chance design Very useful on railway infrastructure and mobile phone tower installations Very useful on railway infrastructure and mobile phone tower installations ‘Screwfast’ piles ‘Screwfast’ piles

12. Ischebeck-type piles ‘Self-drilling’ piles and nails ‘Self-drilling’ piles and nails Paul Woodfield has more details Paul Woodfield has more details

13. Dynamic load testing As an addition to static load testing As an addition to static load testing Mike Turner has more details Mike Turner has more details