OVERVIEW
PERFORMANCE OF
HOUSES SUBJECTED
TO BLAST VIBRATIONS
1. Introduction
2. Project objectives
3. Static testing
4. Shaking table specimen design
5. Results - shaking table test
David Heath1
Dr. Emad Gad1,2
Prof. John Wilson2
1
2
6. Conclusions
The University of Melbourne, Victoria, Australia
Swinburne University of Technology, Victoria, Australia
INTRODUCTION
INTRODUCTION
“Response of residential structures to blast vibrations”
- commenced 2000
- complaints from nearby residents
Lilydale
Mill Park
• Australia – world’s largest exporter of coal
Lysterfield
Kilsyth
• $22.5 billion (AUD) during 2006 – 2007
(19% commodity exports)
Bacchus Marsh
Colac
Geelong
Langwarrin
• Blasting - fracture rock
- Improves efficiency
Wollert
Pakenham
Oaklands Junction
0
500
Scale (metres)
1000
1
MINE AND QUARRY BLASTS
PROJECT OBJECTIVES
¾ Identify the relationship between the level of vibration and
structural drift
Modes of Response
(Flexural)
¾ Establish the relationship between drift and damage of nonstructural components
- Plasterboard (interior)
- URM veneer (exterior)
(In-plane)
¾ Compare effects of blasting with environmental loads
Mine
Quarry
Blast
Blast
Blasting
¾
Blasting
The vibrations travel through the ground in the form of
surface and body waves which produce different particle
motions in the soil
¾
The vibrations travel through the ground in the form of
surface and body waves which produce different particle
motions in the soil.
Above
Ground
Structures
Above
Ground
Structures
Airblast
Subsurface
Infrastructure
Blast
holes
Ground
Vibration
Subsurface
Infrastructure
2
Ground Vibration
¾
Compressive Waves
z
z
Ground Vibration
¾
Denoted as P (Primary) they are the fastest type of
seismic wave.
Produce particle motion (vibrations) parallel to its
direction of travel.
Shear Waves
z
z
Denoted as S (Secondary), are the second fastest
type of seismic wave.
Produce particle motion (vibrations) perpendicular to
its direction of travel.
Propagation
Direction
Ground Vibration
¾
Rayleigh Waves
z
z
Rayleigh waves are slower however they tend to
cause more damage as their particle motion is
greater.
Produce a “elliptical” particle motion.
Propagation
direction
Peak Particle Velocity - PPV
¾
The peak particle velocity (PPV) is used to represent the
intensity of ground vibration.
¾
PPV is correlated
to damage and
human discomfort.
discomfort.
¾
The intensity of a
blast is governed
by blast design
and geological
conditions.
V p = Vl + Vt + Vv
3
BLAST CHARACTERISTICS
VIBRATION STANDARDS
“humans are good detectors of vibrations but poor
measuring devices”
El Centro
Earthquake
Typical blast
vibrations
50
~20-30sec.
40
5mm/s
Mine Blast
~4sec.
5mm/s
Peak
Particle
Velocity
(mm/s)
USBM RI 8507
30
BS 7385-2
AS 2187.2-1993
20
ANZEC
10
Quarry Blast
~2sec.
0
1
VIBRATION STANDARDS
10
Frequency (Hz)
40
100
STATIC TESTING (COMPLETED)
Prism tests
Mortar cube
tests
Racking tests (x2)
Triplet tests
Bond wrench tests
4
TEST HOUSE CONSTRUCTION
INSTRUMENTATION
Veneer
- GP veneer ties
- 1:1:6 (C:L:S) mortar
- 230x76x110mm extruded clay units
- 40mm cavity
- 2.3m high masonry
- 2.4m x 2.8m in plan
- 100x100x6mm EA lintels
Frame and Interior
- Timber frame
- Additional bracing
- 1.5T concrete roof mass
- Plasterboard interior
Photogrammetry model
SHAKING TABLE TEST - RESULTS
SHAKING TABLE TEST - RESULTS
Summary of Test
• Total of 564 blasts
• Range of intensity: 1 - 383mm/s
• First in-plane cracking:
- 140mm/s (walls with doors)
- 300mm/s (walls with windows)
• Other damage:
- ties loosened at 85mm/s
- flexural cracking at 140mm/s
370mm/s (East-West)
5
NORTH & SOUTH MASONRY DRIFT
EAST & WEST MASONRY DRIFT
Drift
Drift
1/75
1/100
1/100
1/250
1/250
1/500
1/500
Key:
SWCA1, SWCB1, NWCB1, SWCC1
NWCB2
SWCA2, SWCA3, SWCC2, SWCD, NWCC
SWCB2
SW & NW
uncracked
Key:
SW fully cracked, NW
partially cracked
SW & NW partially
cracked
SUMMARY OF DRIFT
EW & WW
uncracked
EW cracked, WW
uncracked
WWCB2, WWCC
EWCA
EW & WW cracked
EW & WW fully
cracked
EW completely cracked,
WW partially cracked
CONCLUSIONS
AS2187.2 Vibration Limits
Human
Structural
comfort
damage
Threshold
Cracking
Wall
Drift, Δth
Drift, Δcr
Δ5mm/s / Δth
Δ25mm/s / Δth
North
1/700
1/760
South
1/750
1/370
East
1/750
1/860
West
1/870
1/390
2%
1%
3%
2%
6%
5%
12%
13%
33
7.7
Factor of resistance to cracking
(absence of other loads)
EWCB
WWCA1, WWCB1
Maximum permissible deformation of brick veneer: L/600
(AS2870 Australian Residential Slabs and Footings Code)
9A specimen representing a typical brick veneer house has been
developed and subjected to simulated uniaxial ground vibrations
9The threshold drift for the onset of damage has been identified as
- 1/870 for walls with doors
- 1/750 for walls with windows
(less than 1/600 serviceability limit prescribed in
AS2870 Residential Slabs and Footings code)
9186mm/s discrepancy at first cracking between the two directions
highlights the need for industry displacement based limits
9Maximum drift of the test house to vibrations at existing vibration
limits was well below the drift at the onset of damage
9Parametric study in ANSYS (in progress) to further investigate
influence of other geometries and material properties
6
VIBRATION STANDARDS
“humans are good detectors of vibrations but poor
measuring devices”
Typical blast
vibrations
ACKNOWLEDGEMENTS
• Terrock Consulting Engineers (project partner)
• ARC linkage grant (No. LP0211407)
• ACARP
50
40
Peak
Particle
Velocity
(mm/s)
USBM RI 8507
30
BS 7385-2
AS 2187.2-1993
20
ANZEC
10
0
1
10
Frequency (Hz)
40
100
7