Jan Ekström

PhD

Soil mechanics and

geotechnical

engineering

Project:

BanaVäg i Väst

www.banavag.se

22010-10-22

Göteborg -Trollhättan

•Length approximately 70 km

•Four-lane highway E45.

•Two track railway (speed 250

km/hr)

•50 bridges and tunnels

•Cost 1 000 000 000 Euro

Geotechnical challenge

•0 –100 m of soft clay

•Settlement of present highway is

up to 1,0 m in 40 years

•Geotechnical cost:

approx. 100 0000 000 Euro

32010-10-22

Surte

visit today

Year 2007

Year 2012

For

slow

trafic

Two

tracks

Single

track

Surte

Old

landslide

area

42010-10-22

52010-10-22

Winter 2009/2010

62010-10-22

Important aspects

•Most important = Slope stability –Göta river

•Very soft clay -partly quick clay

•Ongoing settlement 0,5-3 cm/year

•Too high water levels today

•Erosion

•Future climate change

72010-10-22

Lime-cement columns

Lime

cement

columns

Lime

cement

columns

Local

service

road

New

railway

double

track

Göta

river

New E45

Highway

Bedrock

Soft clay

Present

E45

Present railway

82010-10-22

Necessary to build all new highway/railway track on soil

improvement or light fill material

Improvement methods used i the Göta river valley

•Embankment piles of wood or precast concrete piles

(expensive)

92010-10-22

Lightweight expanded clay aggregates (LECA)

ADFASDFASDFASDFASDF

Note: If located under water uplift stability problems

10

2010-10-22

Lightweight fill material EPS

(EPS =expanded polystyrene)

Note: If under water uplift stability problems

11

2010-10-22

•Dry method –Scandinavian countries

•Wet method –Europe

Clay stabilisation with lime and cement

Almost perfect columns -dry method

in very soft clay

Perfect columns -dry metod

in medium soft clay

12

2010-10-22

Pattern for railway: Each circle is one column

Green colour = performed Red colour = remaining

13

2010-10-22

Lime cement columns facts:

Diameter

:500 –1000 mm

Depth

:max 25 m

Mixture/m:

15kg cement

+15 kg lime

Raise

:25mm/rotation

Rotation:

160 r/min

Mixing

Tool

14

2010-10-22

15

2010-10-22

Installation of

lime-cement columns

without temporary road

(temporary road is

excavated after

installation)

16

2010-10-22

With temporary road

during construction

•Stability of machines Ok

•Better quality of columns

•Less settlement

17

2010-10-22

Successful installation

top of columns after

excavation of temporary

filling material

What happend ?

–the column disappeared

18

2010-10-22

•Geotechnical adviser board consisting of

professors in geotechnical engineering

•Automatic measurement of movements and

porepressures 24 hours (day and night)

•Automatic SMS to responsible geotechnical

engineer and site engineer if exceeding

threshold value of movements (x,y,z) or

porepressures (day and night)

•Always all meaurements analysed and

reported from contractor to Swedish

Transport Administation once a week

•Description of all geotechnical temporary

work and calculations must be sent to the

client for approval at least 10 days before

starting

Geotechnical control during construction

Example of horisontal

movements (mm) with depth

(m)

Horisontal movement mm

19

2010-10-22

Example of

improvement of the

shear strength in clay

after mixing with lime

and cement

before:

clay with a shear

strength of 8-10 kPa

(10 kiloPascal=1ton/m2)

after soil improvement:

100-150 kPa

Shear strength (kPa)

20

2010-10-22

Soil improvement by lime-cement columns

Usually to 15-18 m depth now to 25 m depth (clay to 0-100 m)

Load corresponding to heavy fill 2,5 m

Check:

Stability

Settlement behaviour

Test embankments 2000-2007

21

2010-10-22

Thank You !

New railway

two tracks

Old railway=

Location for

new highway

Old highway =

location for noice

protection barrier

22

2010-10-22

You find a helmet and notice west

to borrow in the bus

According to our rules:

When outside of bus at the construction site

Helmet and notice west must be used