inspecta the use of driven precast concrete piles in finland

December 17, 2014 1

DFI INDIA 2014

DFI INDIA 2014

1. Background • Typical soiltypes in Finland • Piling methods used in Finland • Used piling equipment • Piletypes • Geotechnical and structural design 2. Case 1: Railway project ”Kerava-Lahti” direct line 3. Case 2: Construction project ”Porin puuvilla” shopping center 4. Conclusions

December 17, 2014 2

The use of driven precast concrete piles in Finland

Finland Population: 5 445 883 (2013) Capital: Helsinki Weather: usually bad (below zero) Soil conditions: Relatively easy • Interior hard soils moraine and bed rock usually relatively low • With coastlines ususally clay layers

10-50 m and bedrock

15 November 2013 3

DFI India 2014 The use of driven precast concrete piles in Finland

DFI INDIA 2014

Soil conditions in Finland • Typical soil layers from bottom

– Bedrock and moraine – gravel and sand – Silt and clay – Topsoil

• The load bearing layer for piles are usually moraine or bedrock (usually in 10 to 20 m, with coastline up to 50 m)

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DFI INDIA 2014

Used piling methods in Finland: • Driven Precast concrete piles (most common) • Driven Large diameter steel pipe piles (most common in the Bridges) • Driven small diameter steel pipe piles (small buildings, and to replace concrete

piles when use is not reasonable) • Drilled steelpiles (usually in special soil conditions / special constructions) • Jacked small diameter steel pipe piles (used usually in conservation or

underpinning) • Bored piles (not commonly used)

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DFI INDIA 2014

Piles are usually driven with 4 t or 5 t hydraulic hammers • The pile cushion is used to reduce tension waves in

the piles and to prevent pile head damage • Pile cushion usually abot 10-15 cm of wood (birch or

beech) • Dropheight usually 0,2-0,5 m depending pile lenght • End bearing piles are usually driven to 10-30 mm / 10

blows (usually the total amount of blows to pile varies from few hundred to thousand)

• Maximum lenght of the pile element is limited to 15 m • In Finland at the moment only Junttan Hammers are

in use in this hammer category

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DFI INDIA 2014

December 17, 2014 7


DFI INDIA 2014

Standard pile types • Standard pile types used in Finland are 250x250 mm, 300x300 mm and 350x350

mm • There are also few differend kind of reinforcement in the piles, depending on the

pile loads • Conrete strenght 45 to 50 MPa • Reinfocement A500HW / A700HW • The lenght of the pile elements available from 3m to 15m

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DFI INDIA 2014

Pile splices • In Finland the mechanical splices are used for precast concrete piles • The structural design of splice is designed so, thet splice has the same moment

capacity as the pile • Splices are tested according to European standard EN 12794 (Impact blow test

and bending test)

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DFI INDIA 2014

EN 12794:

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DFI INDIA 2014

• Pile is first driven to bedrock or as in the picture steelbox which lies on a concrete block.

• 1000 blows with 28 MPa average compression stress (stress is measured for example with PDA strain transducers during the test)

• The inclination between Joint halves is measured at the start of the test and after 500 blows and at the end of test (which should be less than 1:150)

• After impact blow test pile is lifted from the ground for further tests



DFI INDIA 2014

Impact blow test and bending test



DFI INDIA 2014

Rock shoe • In Finland the rock shoe is used in the most cases (if pile is supposed to support

on bedrock or stony soil) • Rock shoes are tested with Impact blow test and bending test (national

requirement – same impact load test as for he splice)



DFI INDIA 2014

Geotechnical Design according to EN 1997: Eurocode 7 Design load design resistance • Charasteristic value of resistance is

aclculated with correlation factors

• Desugn value of resistance is calculated with partial safety factor



DFI INDIA 2014

Geotechnical Design according to EN 1997: Eurocode 7 Correlation factors from National annex 1. Static load test 2. Dynamic tests 3. Calculations from soil investigation data



DFI INDIA 2014

Geotechnical Design according to EN 1997: Eurocode 7 Partial safety factors factors from National annex: Pile toe (Compression) 1,2 Pile shaft (compression) 1,2 Pile total (compression) 1,2 Pile shaft (tension) Short term 1,35 Long term 1,5



DFI INDIA 2014

The most common way in Finland to make dynamic tests for the pile and make the geotechnical design. For example the maximum design load of 300c pile is 1124 kN and 50% of piles will be tested on site: In tests the target capacity (mean)1,45*1,2*1124 kN = 1956 kN (min value 1753 kN) In this case the geotechnical safety factor is 1,74 (there is also safety in the loads so total safety factor is about 2,4-2,6)



DFI INDIA 2014



DFI INDIA 2014

The end of drive criteria could also be calculated with wave analysis program • Pile is asssumed to be end bearing pile 80% of

resistace is on toe • Hammers and hammer cushions are taken from

programs database • It is assumed that pile cushion is a bit worn (not

new, but not at the end of life) • Soil parameters (quakes and damping factors)

are taken from resarch results from Finland and Sweden



DFI INDIA 2014



DFI INDIA 2014



End of driving criteria is calculated with wave analysis program for 4 and 5 tons hammers (non accelerated and accelerated hammers) and different pile lenghts. • If you have 20 m piles (250a) and accelerated 4 tons hammer and the pile design

load load 605 kN (PTL3), you should drive the pile to 15mm/10blows with 0,25 m dropheight to meet the requirements.

DFI INDIA 2014



How about with neighbour countries to Finland: • Sweden and Norway uses quite similar methods for piling (the most popular is to

use driven precast concrete piles). In both countries Eurocode is used for design, but both have also national codes for piling (Norway: Peleveiledning Sweden: Bro)

• In Baltic Countries (Estonia Latvia and Lithuania) precast concrete pile is not so popular, CFA-piles and steel pipe piles are used even commonly

• In Russia all kind of piling methods are used. When using pre cast concrete piles no mechanical splices are used. Piles are spliced by welding joints (casted steel plates in the pile heads)

DFI INDIA 2014

Case 1: Direct line Kerava-Lahti • Lenght of the track 74 km (totally new track 63 km) • Maximum speed on track 220 km/h • Bridges 76 • About 12 km track runs on a bridge or a bridge-like reinforced conrete slab • Over 700 km of driven concrete piles (63 000 m³)



DFI INDIA 2014

Case 1: Direct line Kerava-Lahti • Shedule for piles 12/2002 to 5/2005 • Track ready to use 9/2006 • Budget 331 M€

Quality control for piles: • Pile capacity will be tested dynamically

from 2,5% of all piles • Integrity test will be done to all piles with

low strain method



DFI INDIA 2014

Dynamic tests: • In year 2002-2005 eurocode was not

used in Finland, • The national geotechnical design was

still used which based on total safety factors

• Most of the piles were 300x300 and the allowable load for piles was 810 kN

• The total safety factor of 2,0 was used with dynamic tests so the target capacity in the dynamic measurements was 1620 kN



DFI INDIA 2014

Dynamic tests: • During the years 2003-2005 totally 407

dynamic tests were made for the concrete piles (Tampere University of Technology)

• The target capacity were 1620 kN and the end of drive criteria varied from 15-25 mm / 10 blows (depending on hammer, dropheight, lenght of the pile and soil conditions)

• Maximum leghts about 40 m and shortests piles approximately 8 m



DFI INDIA 2014

Integrity testing for the piles were made by low strain method • It is possible to see major defects in the

pile • Sometimes the pile splice disturbs the

signal and the lower pile segments can not be seen in the velocity curve

• Signal is sometimes ”noisy” and filters shoud be used so that main things are still visible (also damages can be filtered, which is not the intention)

• Sometimes signal has to be magnified to get the toe reflection

• The new ”classification” of damages was introduced in this project to make reporting easier



Low Strain method DFI India 2014

09/09/2014 Teemu Riihimäki

Pile lenght L

2L/c

Sttress Wave is caused by hand held hammer, and at the same time accreleration is measured on the top of the pile

Damage is detected at time 2x/c

Toe reflection at time 2L/c

Damage at depth X

DFI INDIA 2014



DFI INDIA 2014

During the years 2003-2005 totally 13 725 integrity tests were made for the concrete piles (Tampere University of Technology) • The percentage of rejected piles was

less than 0,5% • Most of the piles damaged during the

driving especially in the soils which contained boulders and stones

• Sometimes the pile cushion was the reason for the damages

• Some of the piles were damaged after driving, when excavators were digging the soil around piles



DFI INDIA 2014

As a conclusion • The railway was manufactured in

schedule and in the budget • The piling with driven prefanricated

concrete piles was a sucsess in this project

• In the sites was in the ”best” time about 20 piling machines

• At the moment 79 trains / day and about 1 million passengers per year



DFI INDIA 2014

Case 2: Puuvilla shopping center • Totally 100 000m2 shopping center • Rental shopping area 43 000 m2 • Amount of shops 75-85 • Budget 110 meur



DFI INDIA 2014

Case 2: Puuvilla shopping center • Piling schedule 1/2013 -5/2013 • Totally 3000 piles (about 100 000m) • Piletypes 250x250, 300x300 and 350x350 average lenght 33m (two splices, three

pile elements) Quality control for piles: • Pile capacity will be tested dynamically from 2% of all piles (about 60 piles) • Piles design loads

– 250x250mm 513 kN target capacity 1,6*1,2*513 kN = 985 kN – 300x300 mm 741 kN target capacity 1,6*1,2*741 kN = 1423 kN – 350x350 mm 1008 kN target capacity 1,6*1,2*1008 kN = 1935 kN

• Integrity test will be done if on site quality management or piling contactor suspects defects on piles



DFI INDIA 2014

Typical measured stresswaves:



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Integrity problems after excavating • After excavating the piling contactor suspected problems with driven piles • Integrity tests were made to find out if piles had been damaged during the

excavation



DFI INDIA 2014



DFI INDIA 2014

Integrity problems after excavating • After excavating the piling contactor suspected problems with driven piles • Integrity tests were made to find out if piles had been damaged during the

excavation



DFI INDIA 2014

As a conclusion • The Shopping center was in schedule and the costs were like in budget • Only few (about 10 piles) of 3000 piles damaged during the installation or other

way • In this case the piling schedule was quite tight and at the best time 5 piling

machines were driving at the same time in the quite smal area • Piles came from 3 different factories to make the schedule possible



DFI INDIA 2014

Conclusion driven precast concrete piles in Finland • Driven precast concrete piles are the most economical solution in most cases in

Finland about 75% of projects is made by precast concrete piles • Pile type should be selected correctly to soil conditions, lots of different solutions

shoud be considered (There is no one right solution which fits everytime) • Shedule and budget are important (Time is money!) • Standard pile types makes deign easier • Testing is important (integrity and the capacity of the installed pile is the main

issue) • Quality is important during the whole piling process (next slide)




Trust and quality in each step of the piling process

Final construction

• Final construction is as designed and safe

Piling machine • Quality of manufacturing • Inspection of machine • Suitability of piling

machine to the site conditions and piletype

Pre- construction

phase • Design of

construction in accordance standards

• Setting quality limits for the final construction

• Setting testing methods for the quality

Construction phase

• Supervision • Monitoring • Testing of the driven

piles • Capacity • Integrity

Pile • Quality of materials • Quality of pile parts

manufacturing • Quality of

manufacturing piles • Testing of the piles,

pileparts and materials

DFI INDIA 2014



Thank you !

inspecta the use of driven precast concrete piles in finland

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