vibration on the kapiti coast

Did the earth move for you?

Vibration on the Kapiti Coast Paul Busing - Kapiti Coast District Council

Introduction

• Vibration upsets people

and can damage

buildings.

• Rarity of exposure.

• Concerns over assets.

• Not as predictable.

• Fear of the unknown.

Terminology

• PPV – Peak Particle Velocity

– Greatest instantaneous particle velocity

during a given time interval.

• SSCVMP – Site Specific Construction

Vibration Management Plan.

• IGA – In General Accordance.

RMA context

• Vibration is defined as noise.

• Section 16 – duty to avoid unreasonable noise.

• A lot of District Plans do not have vibration standards.

• There is no NZ standard for construction vibration.

– NZS/ISO 2631-2:1989 was withdrawn in 2003

• Most projects use either:

– British Standard BS 5228-2:2009

– German Standard DIN 4150-3:1999

– Australian Standard AS 2436:2010

Human Response to Vibration

• Annex B of the British Standard note:

• 0.14 mm/s Just perceptible in the most sensitive situations.

• 0.3 mm/s Just perceptible in residential environments.

• 1.0 mm/s Will cause complaints in residential environments, but

tolerated if residents given prior warning and explanation.

• 10 mm/s Intolerable for any more than a very brief exposure to this

level.

Building Response to Vibration

• DIN4150-3:1999 states “Experience has shown that if these values are complied with,

damage that reduces the serviceability of the building will not occur.”

• Short and long term vibration are defined by the properties of the vibration signal and

not the time frame

What’s happening on the Kapiti

Coast

What is happening on the Kapiti

Coast

What is happening on the Kapiti

Coast

What is happening on the Kapiti

Coast

Management of Vibration

• Board of Inquiry conditions based around both

human nuisance and cosmetic damage.

Receiver Details Category A Category B

Occupied

dwellings

2000h-0630h 0.3 mm/s PPV 1 mm/s PPV

0630h-2000h 1 mm/s PPV 5 mm/s PPV

Other occupied

buildings

0630h-2000h 2 mm/s PPV 5 mm/s PPV

All other

buildings

Vibration -

continous

5 mm/s PPV 50% of Line 2

values in Table B.2

of BS 5228-2:2009

Management of Vibration

• If over Cat A – expert to assess and manage

vibration to stay within Cat A if practicable.

• If not practicable, then undertake continuous

monitoring and comply with Cat B.

• If not practicable to comply with Cat B, then

prepare a SSCVMP.

Management of Vibration

• SSCVMP needs to note:

– Time and duration.

– Equipment used.

– Predicted levels.

– Dwellings where non-compliance will occur.

– How affected persons are to be consulted.

– Alternative management and mitigation

measures.

Monitoring equipment • 3 axis geophone

• Transverse

• Longitudinal

• Vertical

Monitoring equipment

Monitoring equipment

Example – Removing Sheet Piles

8.7mm/s PPV 19-20Hz @ 30m

– Piles welded together

under friction.

– Real time monitoring

picked up issue

developing.

– Works terminated and

piles cut off and left in

ground.

Example – Dynamic Compaction

Example – Dynamic Compaction

Site 1

Site 2

Work

site

Measurements – Dynamic

Compaction

• Site 1 – 161m – 2.09 mm/s PPV @ 7-10Hz.

• Site 2 – 172m – 3.56 mm/s PPV @ 7-10 Hz.

• 70% higher readings even though 11m further

away.

• Equipment specific.

– 11 ton tamper in free fall from 5-6m

– 13 ton tamper on cable from 10m

Example – Dynamic Compaction

Starting and stopping

• Measured vibration from a vibrating roller, showing start up, steady state operation and run

down (Crabb and Hiller 2002)

Damage to Buildings

• DIN4150-3:1999 states: “Experience has

shown that if these values are complied

with, damage that reduces the

serviceability of the building will not occur.”

Damage to Buildings

• Serviceability reduced if:

– cracks form in plastered surfaces of walls.

– existing cracks in the building are enlarged.

– partitions become detached from load bearing walls

or floors.

• Indirect damage may result from differential movements

caused by soil settlement due to densification

[settlement].

Damage observed

Damage observed

Damaged Observed

Damage observed

Damage observed

What worked

• Communication.

What worked

• Communication about what is going to happen

when and where.

• Communication that their house will not fall

down.

– Ground borne noise/re-resonated noise

• Communication so constructors knew about who

was at home, worked from home, worked night

shifts.

• SSCVMP - people moved out or given respite

options.

What worked

• Pre-condition building surveys

• Communication resulted in changes in

methodology

– Oscillating vs Vibratory Roller

• No structural vibration mitigation measures used

so far

• IGA - Refused the use of a certain methodology

in a certain location.

– Dynamic Compaction within 30m of a house.

Points of interest

• Poor communication = more problems

• Two moderate earthquakes during the

project…..who caused the damage? Who

pays?

• Self monitoring – does it work?

– Trust required plus auditing

• Contamination of readings

– Frequency is the key

Points of interest

• Adaptive management and IGA.

– Fluidity requires vigilance.

• Compaction of peat/lowering of water

table.

• How will the building remediation process

work?

– Will the amount of monitoring impact on

peoples claims?

Points of interest

• No total vibration exposure limit.

– 1mm/s PPV could be unreasonable if it goes

on for 30 consecutive days.

• Frequency is important.

– Resonance in structures at low frequencies.

• Removing the noise lessens the

perceived impact of the vibration.

– Re-resonated noise from flues/china

cabinets.

Points of interest

• There appears to be a significant amount

cosmetic damage occurring below the

5mm/s PPV threshold.

• Is this a greater settlement issue or an

actual vibration issue?

• Densification of sand by vibration is well

documented.

Summary

• Compliance with standards do not stop

nuisance complaints

• Ensure good communication

• Vibration is not always predicable

• You can’t beat continuous monitoring in

contentious situations.

• Equipment specific monitoring

Relevant Documents

• State highway construction and maintenance noise and vibration

guide – NZTA August 2013

• Ground vibration from road construction May 2012 – NZTA techincal

research report 485

• Ground Improvements – Third Edition – Edited by Klaus Kirsch and

Alan Bell – ISBN -13: 978-0-203-83897-6

• NZS 6806:2010 – Acoustic – road – traffic noise – new and altered

roads

• http://acoustics.ntza.govt.nz – online tools

Questions?