Carlos H. Reyes - Senior Consultant James T. Nelson - Vice President

Carlos H. Reyes - Senior Consultant James T. Nelson - Vice President

Wilson, Ihrig & Associates, Inc.Oakland, California

www.wiai.com

Evaluation of Vibration Mitigation Measures to Control Groundborne Noise from Underground Transit

TRB W#171

2

OutlineOutline

IntroductionBrief review of the projection modelResults of the analysis and preliminary recommendationsReview of the additional analysis using a theoretical modelConclusions

IntroductionBrief review of the projection modelResults of the analysis and preliminary recommendationsReview of the additional analysis using a theoretical modelConclusions

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IntroductionIntroduction

Silicon Valley Rapid Transit Project (SVRTP)Extension from Fremont to San José, CAHeavy rail SystemCurrently finishing RDEIRWIA participate during Preliminary Engineering (PE)PE ended during summer of 2006 26 Km extension projectConstruction cost of $4.7 Billion (2005 dollar)

Silicon Valley Rapid Transit Project (SVRTP)Extension from Fremont to San José, CAHeavy rail SystemCurrently finishing RDEIRWIA participate during Preliminary Engineering (PE)PE ended during summer of 2006 26 Km extension projectConstruction cost of $4.7 Billion (2005 dollar)

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8.6 Km undergroundDouble bored tunnel (6,900 m) Cut and cover (at 3 stations - 990 m)

Design speed: 72 Km/h and 105 Km/h Base alignment + 2 options at Coyote Creek

8.6 Km undergroundDouble bored tunnel (6,900 m) Cut and cover (at 3 stations - 990 m)

Design speed: 72 Km/h and 105 Km/h Base alignment + 2 options at Coyote Creek

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Project TimelineProject Timeline

Preliminary evaluation of impacts and mitigation options

Mitigation options considered:Highly resilient direct fixation fastener (HRDF)Rail suspension fastener (RSF)Isolated slab track (IST)Floating slab track (FST)

Additional study of mitigation optionsResiliently supported tie (RST)High attenuation RST (HARST)

Preliminary evaluation of impacts and mitigation options

Mitigation options considered:Highly resilient direct fixation fastener (HRDF)Rail suspension fastener (RSF)Isolated slab track (IST)Floating slab track (FST)

Additional study of mitigation optionsResiliently supported tie (RST)High attenuation RST (HARST)

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Projection ModelProjection ModelMethodology follows the FTA procedure for detailed analysisVibration: three main components plus adjustments

Groundborne noise

Methodology follows the FTA procedure for detailed analysisVibration: three main components plus adjustments

Groundborne noiseLv = Lfd + TM lineal + Cbuilding+ Adjust. + Design Factor

LA = Lv + Krad + KA-wt

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Force Density Level (Lfd)Force Density Level (Lfd)Characteristic of the system (vehicle)

Track type (ballast, direct fixation track, etc)

Speed

0

10

20

30

40

50

60

4 8 16 32 63 125 315 630

Frequency (Hz)

Forc

e D

ensi

ty L

evel

dB

re:

1

lb/ft

1/2

FDL HRDF at 105 km/h

FDL RSF at 105 km/h

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Line Source Transfer Mobility (TM)Describes the soil response to vibrationSoil

Alignment lie on alluvial deposits with clays, silts clays, sandy clays, and silts down to 30 m below grade and pockets of sands in between.

SVRTP:Measured TM on 9 locationsMeasurement depths varied between 15 m y 37 m

Line Source Transfer Mobility (TM)Describes the soil response to vibrationSoil

Alignment lie on alluvial deposits with clays, silts clays, sandy clays, and silts down to 30 m below grade and pockets of sands in between.

SVRTP:Measured TM on 9 locationsMeasurement depths varied between 15 m y 37 m

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Line Source Transfer Mobility (TM)Borehole LocationLine Source Transfer Mobility (TM)Borehole Location

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Line Source Transfer Mobility (TM)Line Source Transfer Mobility (TM)

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Building Vibration Response (Cbuilding)Foundation coupling lossFloor resonance (amplification)

Building Vibration Response (Cbuilding)Foundation coupling lossFloor resonance (amplification)

-20

-10

0

10

20

4 8 16 31.5 63 125 250 500Frequency (Hz)

Rel

ativ

e V

ibra

tion

Lev

el -

dB

Single-Family 1st FloorSingle-Family 2nd FloorMulti-Family 2nd FloorTownHome 2nd Floor

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Adjustment Factors1) Soil-Tunnel interaction Adjustment Factors

1) Soil-Tunnel interaction

-20

-10

0

10

6.3 12.5 25 50 100 200

Frequency (Hz)

Rel

ativ

e L

evel

- dB

13

0

2

4

6

8

10

12

0 20 40 60 80 100Distance (m)

Rel

ativ

e V

ibra

tion

Lev

el -

VdB

Adjustment Factors2) Turnouts+10 dB d<15 m+[10-15log(d/15)] 15m <d< 50 m+0 dB d>50 m

Adjustment Factors2) Turnouts+10 dB d<15 m+[10-15log(d/15)] 15m <d< 50 m+0 dB d>50 m

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Vibration CriteriaVibration Criteria

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Groundborne Noise CriteriaGroundborne Noise Criteria

Special Buildings

25 dBA25 dBAConcert Halls, TV Studios & Rec. Studios

48 dBA43 dBA40 dBACategory 3

38 dBA30 dBAAuditoriums

45 dBA35 dBATheaters

43 dBA38 dBA35 dBACategory 2

N/AN/AN/ACategory1

Infrequent Events

Occasional Events

Frequent Events

Land Use Category

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Analysis ResultsAnalysis ResultsGroundborne vibration levels below criteriaGroundborne vibration levels below criteria

1020

3040

50

60

70

80

4 8 16 31.5 63 125Frequency (Hz)

Vib

ratio

n V

eloc

ity L

evel

- R

e 10

μin

Multifamily 2nd levelSingle Family raised floor 1 storyFire Station

No Vib. mitigationmeasures necessary

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Analysis Results (cont…)Analysis Results (cont…)48 buildings (132 individual units) with potential for groundborne noise impact48 buildings (132 individual units) with potential for groundborne noise impact

0

10

20

30

40

50

60

6.3 10 16 25 40 63 100 160 250Frecuency (Hz

Multifamily 2nd levelFire StationSingle Family raised floor 1sto

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Preliminary Mitigation MeasuresPreliminary Mitigation MeasuresHighly Resilient Direct Fixation (HRDF)Dynamic stiffness: 14 MN/m Dynamic/static ratio = 1.25

Highly Resilient Direct Fixation (HRDF)Dynamic stiffness: 14 MN/m Dynamic/static ratio = 1.25

0

10

20

30

40

50

60

6.3 10 16 25 40 63 100 160 250Frecuency (H

Multifamily 2nd levelFire StationSingle Family raised floor 1

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Preliminary Mitigation MeasuresPreliminary Mitigation MeasuresRail suspension fastener (RSF)Dynamic stiffness: approximately 8.4 MN/mDynamic/static ratio: 3.4 ExamplesDelta DF and Vangard

Rail suspension fastener (RSF)Dynamic stiffness: approximately 8.4 MN/mDynamic/static ratio: 3.4 ExamplesDelta DF and Vangard

Delta DF - ATP

Vangard - Pandrol

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Preliminary Mitigation MeasuresPreliminary Mitigation MeasuresRail suspension fastener (RSF)(cont.)Rail suspension fastener (RSF)(cont.)

0

10

20

30

40

50

60

6.3 10 16 25 40 63 100 160 250Frecuency (H

Multifamily 2nd levelFire StationSingle Family raised floor 1st

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Preliminary Recommendations on Vibration Mitigation

Preliminary Recommendations on Vibration Mitigation

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Additional Mitigation Measures Evaluated

Additional Mitigation Measures Evaluated

Isolated Slab Tracks (IST)Similar to floating slabImplemented in Toronto & Sao PauloPotential design:25 to 30 cm thick slab over Sylomer or Ballast MatEstimated reduction(preliminary) 10 - 14 dBA

Isolated Slab Tracks (IST)Similar to floating slabImplemented in Toronto & Sao PauloPotential design:25 to 30 cm thick slab over Sylomer or Ballast MatEstimated reduction(preliminary) 10 - 14 dBA

0

10

20

30

40

50

60

6.3 10 16 25 40 63 100 160 250Frecuency (H

Multifamily 2nd levelFire StationSingle Family raised floor 1 st

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Additional Mitigation Measures Evaluated

Additional Mitigation Measures Evaluated

High Attenuation RST developed for Metro Hong Kong

High Attenuation RST developed for Metro Hong Kong

Wider block

Thicker Pad

Wider block

Thicker Pad

24 BART adopted resiliently supported half-tie (RST) as their design standard

Additional study was needed to evaluate a rail support track that:

Complies with their standard (RST), andReduce groundborne noise impacts

BART adopted resiliently supported half-tie (RST) as their design standard

Additional study was needed to evaluate a rail support track that:

Complies with their standard (RST), andReduce groundborne noise impacts

Concrete block

Rubber boot

Block:640mm x 260mm x 200 mm

Boot 12 mm thickness

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Additional Parametric StudyAdditional Parametric StudyGoal: To determine if a single track system could mitigate ALL groundborne noise impacts

Numerical model:Discrete rail support Vehicle ModelParallel impedance modelTunnel invert forces

Goal: To determine if a single track system could mitigate ALL groundborne noise impacts

Numerical model:Discrete rail support Vehicle ModelParallel impedance modelTunnel invert forces

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Additional Parametric StudyAdditional Parametric StudyTrack Support Systems Evaluated:

RST Original (pad stiffness 98 MN/m, mass block 82 kg) RST STD (“finned boot”, pad stiffness 44 MN/m, mass block 82 kg)HARST (High Attenuation RST, pad stiffness 22 MN/m, mass block 109 kg)HARST_SP (softer pad, pad stiffness 11 MN/m, block mass 109 kg)HRDF (pad stiffness 14 MN/m)

Track Support Systems Evaluated:RST Original (pad stiffness 98 MN/m, mass block 82 kg) RST STD (“finned boot”, pad stiffness 44 MN/m, mass block 82 kg)HARST (High Attenuation RST, pad stiffness 22 MN/m, mass block 109 kg)HARST_SP (softer pad, pad stiffness 11 MN/m, block mass 109 kg)HRDF (pad stiffness 14 MN/m)

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ModelsModelsDiscrete Rail Support

Exact solutions of the Bernoulli-Euler model for discretely supported beamsIdeal spring-mass system

Truck ModelTruck represented by a 22 DOF system of wheel, axle, inertia block, motor, gear box, break and 1/2 car body

Discrete Rail SupportExact solutions of the Bernoulli-Euler model for discretely supported beamsIdeal spring-mass system

Truck ModelTruck represented by a 22 DOF system of wheel, axle, inertia block, motor, gear box, break and 1/2 car body

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Combined Model Combined Model Models were combined to determine force transmissibility

Force transmitted to rail head

Models were combined to determine force transmissibility

Force transmitted to rail headFr(ω) = Kr(ω) U(ω) = -Kr(ω)[Kr(ω)+ Kv(ω)]-1 Kv(ω)δ(ω)

Fnet(ω) = ∑ Tr(ω)Fr(ω)

|FTOTAL(ω)|2=|F1net(ω)|2+|F2

net(ω)|2+|F3net(ω)|2+|F4

net(ω)|2

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Model SchematicModel Schematic

Complete SimplifiedComplete Simplified

30Track ParametersTrack Parameters

84426093139HzRail+Block Resonance

N/A209215261291HzBlock Resonance

N/A2.452.450.820.82Kg-m2Isolation Rotational Inertia

N/A10910982.082.0KgIsolation Mass Top Plate

N/A178178178178MN/mRail Pad Vertical Stiffness

0.03650.250.51.002.22MN-mMain Pad Rotational Stiffness

14.011.022.044.098.0MN/mMain Pad Vertical Stiffness

HRDFHA_RST_SP

HA_RST

STD RST

ORIG RST

UnitParameter

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Expected Reduction LevelsExpected Reduction LevelsResults of the simplified model (re: ORIG_RST)Results of the simplified model (re: ORIG_RST)

-30

-20

-10

0

10

4 8 16 31. 63 125 250 500Frecuency (Hz)

RST_STDHARSTHARST_SPHRDF

32 ConclusionsConclusionsA combination of highly resilient direct fixation fastener and rail suspension fasteners could be a viable solution to eliminate groundborne noise impacts.The parametric analysis indicates that high attenuation resiliently supported track with softer boot and pad HARST_SP could be a uniform solution for the project. However, before adoption by the Project, results will be validated with field measurements.

A combination of highly resilient direct fixation fastener and rail suspension fasteners could be a viable solution to eliminate groundborne noise impacts.The parametric analysis indicates that high attenuation resiliently supported track with softer boot and pad HARST_SP could be a uniform solution for the project. However, before adoption by the Project, results will be validated with field measurements.

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AcknowledgeAcknowledge

Bay Area Rapid Transit (BART)HMM/BechtelBay Area Rapid Transit (BART)HMM/Bechtel