Monitoring of structuresadjacent to geotechnical

works

Joanna Pieczynska, Jaroslaw Rybak

Wroclaw University of Technology

Main ideas

• Sheet piling. – Piling technologies (driving, press-in

method).

• Ground improvement– Technologies – impact on neighborhood.

• Case studies – examples of monitoring

Deep excavations

• Wroclaw – historical city-center

Traditional methods

• Pile driver• Vibrator

Press – in method

Press – in method

• Close, closer …

Deep excavation

• University of Wroclaw• Faculty of Law

How to reduse the impact ?

• Pre-boring

How to reduse the impact ?

• jetting

How to reduse the impact ?

• jetting

Monitoring

0

10

20

30

40

50

60

0 20 40 60 80 100

Frequency [Hz]

Pea

k p

arti

cle

velo

city

[m

m/s

]

cat. 1

cat. 2

cat. 3

Type of property

Peak particle velocity [mm/s]

Continuous vibration Transient vibrations

Ruins, buildings of architectural merit 2 4

Residential 5 10

Light commercial 10 20

Heavy industrial 15 30

Buried services 25 40

Monitoring – Techniczna street

• Daily report – peak particle velocity

Monitoring – Techniczna street

• Daily report – peak particle velocity

Monitoring – Techniczna street

• At 12:33:15 on 5 February 2010 the sensor recorded an excitation increasing in the period of 15 seconds to the value of 200 mm/s, and in the subsequent 15 seconds – incremented by another 50 mm/s. The character of the value was not accidental, but rather illustrated a propagating seismic wave. Unfortunately, the sensor was set at the test range of 0 – 250mm/s and after exceeding this range, it turned off. It is obvious that after the above shown results are marked on the DIN4150 diagram, the effect will considerably differ from all possible safety levels. After the afore-mentioned situation had been recorded, tedious search took place in order to confirm that the seismic wave was truly excited in the neighborhood.

Monitoring – Techniczna street

• Finally, at about 3:00 p.m. the Bobrek – Bytom Centrum Mine provided information that there had been a crump which released a great amount of energy. The mine determined the excitation at the level of 2.7 degrees of the Richter scale. Unfortunately, the caution on the part of the investor did not prevent the neighboring houses from damages; it only saved the geotechnical company from paying damages, as the failure had not been caused by their work

Monitoring – examples

• Powązkowski National Cementary

Monitoring – examples

• Cementary wall

Monitoring of vibrations

• Cementary wall• Graves

Peak particle velocities

Peak particle velocities / frequency

0

10

20

30

40

50

60

0 20 40 60 80 100

Częstotliwość [Hz]

Am

pli

tud

a p

ręd

koś

ci d

rgań

[m

m/s

]

kat. 1

kat. 2

kat. 3

Monitoring – dynamic replacement

• Residential house near building site

Monitoring – daily report

Monitoring – bridge abutment

• New built bridge abutment. Problem of vibration impact on early concrete.

Monitoring – daily report

Monitoring – equipmentHeavy noise control

Conclusion

• The analysis of vibrations of the background that permanently influences the monitored structures makes it possible to determine precisely the permissible frequency of vibrations and thus to take into account lower efficiency of works in calculating overall costs.

• Although the monitoring programs may be in practice diversified, complex and perfectly adjusted to even very demanding construction technologies, the difficulty lies in the assessment of the proportions between the real needs, the proper monitoring scope and the financial resources of the investor, who, in the end, pays for such investigation.

• It is however worth emphasizing that the costs of such examination are much lower than the potential damages that may be thus avoided.

Thank you for your attention