Research on The Long Term Performance of Energy Piles®

(Field Installation)

Echo Ouyang, Kenichi Soga

Geotechnical and Environmental Research Group

Department of Engineering

University of Cambridge

Outlines

• Issues being raised from previous experience @ Lambeth College.

• Long term Energy Piles® monitoring programme set up for @ Bankside, London.

• Future prospects and challenges.

Issues to be explored…

• Energy aspect:

– Thermal properties of soil material.

– Efficiency of energy extraction.

• Geotechnical aspect:

– Influence of geothermal energy extraction to the changes in soil material and affects to the adjacent infrastructure.

– Long term thermal cycles to the geotechnical performance of energy piles group.

Long term

monitoring

Future

pro

spects

Field test

Long Term Monitoring Project @ Bankside

• Long term monitoring programme setup.

Pile Info Dry (ε) Wet (ε) Dry (T)

Dia (mm.) 1200

Pile length (m) 30 50 30

Load (kN) 4650 13000 700

No of energy loops 4 4 4

VWSG 20 24 -

OFS - ε(loops) 2 2 -

Thermistor 2 2 -

OFS – T (loops) 2 2Inst

rum

en

-ta

tio

n

Long term

monitoring

Future

pro

spects

field test

Instrumented EPs (Strain & Temperature)PPL = 0.3 mOD

Made Ground

Terrace Deposit

1280 dia.

13

00

50

00

London Clay

70

00

1200 dia.

A A15

00

01

20

00

8H40

-51.0 mOD

8H20

12

00

01

50

00

B B

VWSG * & Thermistor Set

Reinforcement bar

Geothermal tube

Clamped FOS-ε *

FOS-T *

* Vibrating Wire Strain Gauge (VWSG);

* Fibre Optic Sensor, Strain Cable (FOS-ε)

* Fibre Optic Sensor, Temperature Cable (FOS-T)

Section A-A: Cross section of

strain test pile No 203

Section B-B: Cross section of

strain test pile No 203

8H25

8H25

8H40

8H20

1200 dia.

1280 dia.

A A

71

00

-2.625 mOD

15

00

01

50

00

-31.5 mOD

8H40

8H40

500

B B

Section A-A

Section B-B

8H40

8H40

H12

Long term

monitoring

Future

pro

spects

field test

Instrumentations

Strain OFS

Temperature OFS

Optical Fibre Strain Sensors (OFS) Vibrating Wire Strain Gauge (VWSG) and Thermisters

Long term

monitoring

Future

pro

spects

field test

Schematic layoutLong term

monitoring

Future

pro

spects

field test

Pile InstallationLong term

monitoring

Future

pro

spects

field test

Pile Installation – The 50m long Energy Pile®Long term

monitoring

Future

pro

spects

field test

Challenges

• Long term thermal cyclic loading effects on energy piles group.

• Differential settlement control

Time evolution

Dif

fere

nti

al s

ettl

emen

t

Building tilting

Long term

monitoring

Future

pro

spects

field test

Acknowledgements

• University of Cambridge

• Cementation Skanska

• Geothermal International

• Carillion

• Euro Earthwork

Thank you