An investigation into the effects of material properties ... · An investigation into the effects...

An investigation into the effects of

material properties on shear wave

velocity in rocks and soils

Presenter: Natalie Campbell

Co-Authors: Dr Clark Fenton

Sarah Tallett-Williams (PhD Candidate)

Overview

•Background to research

•Database of results

•Findings of research

“What affects the shear wave velocity of a material?”

Purpose of Research

PhD Project to improve site classification for hazard

assessment in the UK, by characterising the 26 strong

ground motion stations within the UK Network

1. Creation of a method of determining Vs30 for sites with

little or no site specific ground information.

2. Trial of this method at a strong ground motion station

site in the UK, and undertake in situ Vs measurements in

order to verify and improve the method.

3. Compilation of a database of Vs values obtained from

studies both within the UK and globally to understand the

controlling factors for Vs in different geological units

4. Investigation of the correlation between depositional

environment, geological age, etc. and Vs.

5. Revision of the original estimation method having

analysed the results from both the test case and the

global database.

6. Use of the refined and verified method to characterise

all other strong ground motion stations in the UK (26

total) and to perform testing as required to verify the

results.

Location of the 26 strong ground motion stations in the UK (Baptie, 2012).

Database Overview

Example: Turkish National Database. Station 0110

Database Overview - source

Total = 6531 VS Records

Field, 3607

Laboratory, 2924

USGS, 534

Turkish Database,

1129

Geological Survey of

Canada, 64

Pacific Northwest Seismic Network (PNSN),

Washington, 249

Industry Sources –

United Kingdom

Sites, 1215

Engineering Geological

Database for TSMIP, 306

NATO Science for

Peace Project – Bucharest,

Romania, 110

Geoscience Data

Repository for Geophysical Data (GSC),

2860

Laboratory database of silicate rocks (Birch, 1960),

64

Refraction, 72

SASW or MASW, 1382

ReMi or MAM, 249

Crosshole, 543

Downhole, 813

SCPT, 262

Suspension P-S, 535

Database Overview – test method

Intrusive

Non-intrusive

(active)

Non-intrusive

(passive)

Piezo-electric Transducer,

2924

Results

Laboratory Tests Field Tests

Rock

Origin of rock

Rock

Origin of rock

Density Fracture spacing

Confining pressure RQD

Weathering

Soil

Depositional environment

Grain size

Rock + Soil Geological age

“What affects the shear wave velocity of a material?”

Presentation of Results

Box and Whisker Plot

Results: Fracture Spacing

0 200 400 600 800 1000

Crushed to highly jointed (5)

Highly jointed (34)

Highly to moderately jointed (12)

Moderately jointed (25)

Moderately to slightly jointed (3)

Slightly jointed (6)

Vs (m/s)

Incre

ase

dfr

actu

rin

g

Turkish Data

6 20 60 200 600 2000 60001 10 100 1000 10000

Fracture Spacing (mm)

BS 5930 + ISRM

Hong Kong

Geoguide 3

Consultant1.

MediumCloseVery CloseExtremely Close Wide Very Wide Ext Wide


MediumCloseVery CloseExtremely Close Wide Very Wide

Eurocode 8MediumCloseVery CloseExtremely Close Wide Very Wide

Govt Dept2. MediumCloseVery CloseExtremely Close Wide Very Wide Ext Wide

USGS ModerateCloseVery Close Wide Very Wide

USBR ModerateCloseVery Close Wide Very Wide Ext Wide

FHWA Very Close Close Moderate Wide Extremely Wide

Crushed Highly Jointed Moderately Jointed Slightly JointedTurkey3.

1. Sinclair Knight Merz

2. Queensland Department of Main Roads

3. Boundaries from Turkish logs are undefined

Reconciling Fracture Spacing

Results: Weathering

0 500 1000 1500 2000 2500 3000

Fr (134)

SW-Fr (97)

SW (29)

MW-SW (40)

MW (58)

HW-MW (45)

HW (18)

CW-HW (12)

CW (28)

Vs (m/s)

Incre

asin

g W

eath

ering

step-change?

Results: Depositional Environment

0 200 400 600 800 1000 1200

Estuarine (114)

Alluvial (1044)

Aeolian (38)

Offshore sediments (58)

Colluvial (151)

Glacial (293)

Residual (23)

Vs (m/s)

Category 1

Category 2

Conclusion

Parameter Effect on Vs Details

Rock origin Yes

Sedimentary rocks had the lowest Vs increasing for igneous and the highest values were

recorded in metamorphic rocks. Relationships were most prominent in the laboratory data. A

significant offset was observed between Vs results determined in the laboratory and field, with

mean laboratory results being up to 4.1 times larger.

Density YesIncreased Vs with increased density. A medium strength (0.3 < R2 < 0.6) correlation was

observed for a linear relationship for each rock origin.

Confining

pressureYes

Significant increase in Vs at low stress levels, less influence at higher stresses, Vs was more

controlled by the discontinuities.

Fracture

spacingYes

Vs decreased with an increased amount of fracturing (decreased fracture spacing). This was

most prominent in the results from the Turkish database and when considering the sedimentary

materials from the USGS database. The trend was not clear for the USGS data set when all

rock origins were included.

RQD No No correlation observed

Weathering Yes

Vs decreased as weathering state increased. For the complete dataset, a 52% decrease in

average Vs was observed as rocks degraded from slightly weathered to moderately weathered.

This boundary was also observed for the sandstone (50% decrease) and limestone subsets.

Depositional

environmentYes

Estuarine, alluvial, aeolian and offshore evironments appeared fairly consistent and resulted in

markedly lower Vs values than the glacial, colluvial and residual environments. This was related

to the likely degree of sorting that occurs for various transport processes.

Grain size Yes Vs increased with increasing grain size (investigated and observed in the alluvial data subset)

Geological ageYes

Vs increased with increasing geological age, particularly observed at the Era level (between

Paleozoic, Mesozoic and Cenozoic). This may be influenced by rock origin, however the

relationship holds for the sedimentary dataset.

References

• Baptie, B. (2012.) UK Earthquake Monitoring 2011/2012.. Report OR/12/092. British Geological

Survey Commissioned Report

• Borcherdt, R. D. (1994) Estimates of site-dependent response spectra for design (methodology and

justification). Earthquake Spectra. 10 (4), 617-653.

• British Standards Institution. (2004b) Eurocode 8: Design of structures for earthquake resistance. Part

1: General rules, seismic actions and rules for buildings. BSI, London.

• Building Seismic Safety Council. (2003) NEHRP Recommended Provisions for Seismic Regulations

for New Buildings and other Structures (FEMA 450). Part 1: Provisions. pp. 17-49.

• Caterpillar. (2012) Caterpillar Performance Handbook. 42nd edition. Illinois, U.S.A., Caterpillar Inc.

• Kim, D. S. & Park, H. C. (1999) Evaluation of ground densification using spectral analysis of surface

waves (SASW) and resonant column (RC) tests. Canadian Geotechnical Journal. 36 (2), 291-299.

• Middle East Technical University - Earthquake Engineering Research Centre. (2014) Strong ground

motion database of Turkiye. [Online] Available from: http://kyhdata.deprem.gov.tr/2K/kyhdata_v4.php

[Accessed 17 June 2014].

• Standards Australia. (2007) AS 1170: Structural Design Actions. Part 4: Earthquake Actions in

Australia. 2nd edition. Sydney, Standards Australia.

• Tallett-Williams, S. (2014) Site classification for seismic hazard assessment: early stage assessment.

Report. London, Imperial College.

• Wolfram Research (2011) Seismic Waves. www.blog.wolfram.com.

Shear Wave Velocity: What?

Seismic Waves

Body Waves

P-Waves (primary, compression, longitudinal)

S-Waves(secondary, shear,

transverse)

Surface Waves

Rayleigh Waves

Love Waves

P-Wave

S-Wave

Shear Wave Velocity: What?

Seismic Waves

Body Waves

P-Waves (primary, compression, longitudinal)

S-Waves (secondary, shear,

transverse)

Surface Waves

Rayleigh Waves

Love Waves

Rayleigh Wave

Love Wave

Shear Wave Velocity: Why?

•Seismic Design

• Site classification for building codes

• Site factors in ground motion prediction equations (GMPEs)

• Characterisation of site conditions at strong ground motion recording stations

• Evaluation of liquefaction resistance

Shear Wave Velocity: Why?

•Other (non-seismic)

• Assessment of rippability

• Assessment of small strain stiffness (G)

• Verification of ground improvement works

• Estimation of vibration propagation due to construction activities

• Crosshole

• Downhole

• SPT-uphole

• SCPT

• Suspension P-S

Measurement of VS

Laboratory Field

Intrusive Non-intrusive

Active

Passive

Shear Wave Velocity: How?

• Seismic reflection

• Seismic refraction

• SASW

• ReMi

• MAM

• Resonant Column

• Piezoelectric Transducers

(Bender elements)

Summary of Advantages and Disadvantages

0 1000 2000 3000 4000 5000

Sedimentary (229)

Igneous (1241)

Metamorphic (1476)

Vs (m/s)

Results: Origin of Rock

Laboratory tests


0 1000 2000 3000 4000 5000

Sedimentary (861 + 229)

Igneous (104 + 1241)

Metamorphic (131 + 1476)

Vs (m/s)

Field tests Laboratory tests

Results: Density

y = 1046x + 716R² = 0.4

0

1000

2000

3000

4000

5000

6000

2 2.5 3 3.5 4

Vs

(m/s

)

Density (kg/m3)

All Data

y = 2030x - 2135R² = 0.6

0

1000

2000

3000

4000

5000

6000

2 2.5 3 3.5 4

Vs

(m/s

)

Density (kg/m3)

Sedimentary

y = 877x + 1252 R² = 0.5

0

1000

2000

3000

4000

5000

6000

2 2.5 3 3.5 4

Vs

(m/s

)

Density (kg/m3)

Metamorphic

y = 1114x + 518R² = 0.3

0

1000

2000

3000

4000

5000

6000

2 2.5 3 3.5 4

Vs

(m/s

)

Density (kg/m3)

Igneous

Results: Confining Pressure

2000

2500

3000

3500

4000

4500

5000

0 100 200 300 400 500 600 700 800 900 1000

Vs

(m/s

)

Confining Stress (MPa)

Greywacke (A) Gneiss (A) Gabbro (A)

Sandstone (B) Eclogite (B) Anorthosite (B)

A: Natural Resources

Canada (2013)

B: Birch (1960)

6 20 60 200 600 2000 60001 10 100 1000 10000

Fracture Spacing (mm)

BS 5930 + ISRM

Hong Kong

Geoguide 3

Consultant1.



MediumCloseVery CloseExtremely Close Wide Very Wide

Eurocode 8MediumCloseVery CloseExtremely Close Wide Very Wide

Govt Dept2. MediumCloseVery CloseExtremely Close Wide Very Wide Ext Wide

USGS ModerateCloseVery Close Wide Very Wide

USBR ModerateCloseVery Close Wide Very Wide Ext Wide

FHWA Very Close Close Moderate Wide Extremely Wide

Crushed Highly Jointed Moderately Jointed Slightly JointedTurkey3.

1. Sinclair Knight Merz

2. Queensland Department of Main Roads

3. Boundaries from Turkish logs are undefined

Reconciling Fracture Spacing

Results: Fracture Spacing

0 500 1000

Crushed to highly jointed (5)

Highly jointed (34)

Highly to moderately jointed (12)

Moderately jointed (25)

Moderately to slightly jointed (3)

Slightly jointed (6)

Vs (m/s)

Incre

ase

d

fractu

rin

g

0 500 1000 1500

Sheared (2)

Very Close (5)

Very close to close (7)

Close (5)

Close to moderate (11)

Moderate (7)

Moderate to wide (7)

Wide (3)

Vs (m/s)

Incre

ase

d

fractu

rin

g

Turkish Data

USGS Data

(Sedimentary)

Results: RQD

0 500 1000 1500 2000

Very Poor (68)

Poor (78)

Fair (58)

Good (39)

Excellent (63)

Vs (m/s)

Ro

ck

Qu

ali

ty RQD Classification

0 – 25% Very Poor

25 – 50% Poor

50 – 75% Fair

75 – 90% Good

90 – 100% Excellent

0

500

1000

1500

2000

0 20 40 60 80 100

Vs

(m/s

)

RQD (%)

Results: Grain Size

0 200 400 600 800 1000 1200

Silt / Clay (169)

Clay / Silt / Sand (367)

Sand (111)

Sand / Gravel (198)

Gravel (4)

Cobbles + Boulders (26)

Clay - Gravel (87)

Vs (m/s)

Incre

asin

g g

rain

siz

e

Results: Geological Age

0 500 1000 1500 2000 2500 3000

Cenozoic (1723)

Mesozoic (375)

Paleozoic (111)

Proterozoic (2)

Vs (m/s)

Incre

asin

g a

ge

Results: Geological Age + Origin

(1485)

(200)

(38)

(51)

(2271)

(243)

(71)

(109)

(2)

0

200

400

600

800

1000

1200

Soil Sedimentary Igneous Metamorphic

Ave

rag

e V

s(m

/s)

Cenozoic Mesozoic Paleozoic Proterozoic (x) No. samples

Liquefaction Resistance

Andrus, R. D. & Stokoe, K. H. (2000) Liquefaction resistance of soils from shear-wave velocity. Journal of Geotechnical and Geoenvironmental Engineering. 126 (11), 1015-1025.

Calculation of Vs30

Silty Clay

Sand

Rock

Vs= 60m/s

Vs= 110m/s

Vs= 900m/s

0m

5m

20m

Method Advantages Disadvantages

Seismic Reflection No borehole required

Well suited for large areas and soils which are difficult to

penetrate

Small source-receiver offsets

No sample recovered

Only effective in layered ground

Seismic Refraction No borehole required

Well suited for large areas and soils which are difficult to

penetrate

No sample recovered

Cannot detect velocity inversion or thin layers

Require relatively large source-receiver offsets

SASW / MASW No borehole required

Suited to sites with collapsible deposits (difficult to drill)

Low geometrical attenuation of Rayleigh waves compared to

body waves (reflection and refraction methods).

No sample recovered

No control over frequencies generated, may be necessary

to use a number of different impulse energy sources to

generate the required range of frequencies

Resolution decreases with depth

ReMi and MAM No borehole required

No active source required

No sample recovered

Crosshole Seismic Boreholes allow sampling of material

Can detect low velocity layers

Can test all soil and rock types

Highly reliable test

Measurement at each depth is independent of other depths

Minimum two cased boreholes required

Downhole Seismic Borehole allows sampling of material


Measurement at each depth is independent of other depths

One cased borehole required

Depth limited by the size of the energy source

SPT-uphole Borehole allows sampling of material


Combine with strength index (SPT) test

One borehole required

Receivers close to the borehole may be affected by the

engine noise of the drilling rig

SCPT No borehole required

Continuous subsurface profiling (CPTu)

Penetration limited by soil strength (refusal)

Suspension P-S Logger Borehole allows sampling of material


Wireline method allows rapid testing at greater depths

One fluid filled borehole required

Issues with cased boreholes, therefore difficult in loose,

collapsible soils

Field Results (by method)

Refraction, 72

SASW or MASW, 1382

ReMi or MAM, 249

Crosshole, 543

Downhole, 813

SCPT, 262

Suspension P-S, 535

Field Results (by quality of data)

High, 1491

Medium, 729

Low, 172


IGN

EO

US

Sources of Uncertainty

SoilIn-situ

measurementTransformation

ModelEstimated Soil

Property

Inherent soil

variability

Data

Scatter

Statistical

Uncertainty

Inherent soil

variability

Measurement

error

Model

Uncertainty

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