Floating Slabtrack Systems in Tunnels A case study with different FST systems Metro Lisbon Red Line Extension Patrick Carels CDM Novitec, President Evanston, IL
Content Project description Vibration mitigation measures N&V measurement campaign and results Conclusions
Project Description Location Residential Buildings Instituto Superior Tecnico (IST) Red Line Extension: 1.4 miles Construction date: 2008-2010
Project Description Typical track type Tunnel Rail type: 50E1 Axle load: 10T/axle 20 thick RC slab Rail fixation system: resilient ties Cstat,railpad = 457 kip/in Cstat, block pad = 57 kip/in Design speed: 38 mph Minimum radius: 330 ft Maximum superelevation: 6
Project Description Vibration study Existing vibration levels: v rms < 10E-6m/s [393.7μin/s] Vibration criteria: Residential buildings: v rms < 30E-6m/s [1181.1μin/s] IST grounds: Equipment mfg.: v ptp < 5E-6m/s [196.9μin/s] IST requirement: v rms < 10E-6m/s [393.7μin/s] Mitigation requirements: performance based Solution type Average Insertion Loss (20-200Hz) 1 30 dbv 2 (transition zone) 30-35 dbv 3 35 dbv
Vibration mitigation measures General approach: Insertion loss philosophy Unit dynamic force excitation REFERENCE Track parameters ISOLATED Track parameters MECHANICAL MODEL IL calc = IL required? c stat,eq c dyn,eq N&V SYSTEM MODEL c stat c dyn RESILIENT MATERIAL parameters: Material Type, Density, Shape factor, Thickness, etc
Vibration mitigation measures General approach: Insertion loss philosophy Performance based requirements Solution type Average Insertion Loss (20-200Hz) 1 30 dbv 2 (transition zone) 30-35 dbv 3 35 dbv Solution type Ceq, dyn (lbf/in³) CDM system 1 62 CDM-TOMAS-M8 2 (transition zone) N&V system requirements 62 CDM-FSP-M10 3 26 CDM-FSP-M9
Vibration mitigation measures System description Resilient material Choice of resilient material type, based upon: Dynamic and static stiffness characteristics Loading characteristics Resistance against harsh environmental conditions found in tunnels: Humidity Oil & greases Temperature High quality resin-bonded rubber material (CDM-RR)
Vibration mitigation measures System description CDM-TOMAS CDM-TOMAS (Track slab On Mats with Adaptable Stiffness) hybrid solution between: Continuous mat/sheets easy installation Discrete resilient support adaptable and optimized stiffness
Vibration mitigation measures System description CDM-TOMAS
Vibration mitigation measures System description CDM-FSP CDM-FSP = Floating Slab Pads, discrete bearings High performance floating slab (lowest dynamic bedding modulus) Disadvantages to continuous support: Additional concrete reinforcement needed Lower lateral stability L-shaped bearings: Dimensions: 4.1 x 1.0 x 2 Width: 1.0 ft Supporting thickness: 2.0 Distance between bearings: 5.9 ft
Vibration mitigation measures System description CDM-FSP Increased lateral stability vs typical bearing thanks to increased supporting area and reduced height K h = (G x S)/h No lateral buffers needed, even in curve
Vibration mitigation measures System description CDM-FSP Installation via prefabricated slabs
Vibration mitigation measures System description CDM-FSP
Noise & Vibration measurements Measurement campaign Timing: 3 months after start of operation Vibration levels on the slabtrack and on the tunnel invert Under train passage Under mechanical impulse Vibration levels in the building nearly vertical and closest to the tunnel Point 1 Local Conditions Near old tunnel entrance N&V Solution CDM-FSP Train Speed 38 mph 2 Near transition CDM-FSP 38 mph 3 Reduced speed - switch 4 Curve EXTRA Near transition CDM- TOMAS CDM- TOMAS ML Reference Track 28mph 28mph 28mph Additional vibration levels on the slabtrack and tunnel invert on the Blue Line as reference
Noise & Vibration measurements Transmission Loss Transmission loss, solution 3 (CDM-FSP) under train passage and mechanical impulse Transmission loss under train passage for different solutions
Noise & Vibration measurements Estimated Insertion Loss
Noise & Vibration measurements Transmission Loss vs Insertion Loss INSERTION LOSS vs. TRANSMISSION LOSS B ref A ref B ic A ic IL = 20 log (B ic /B ref ) TL = 20 log (A ic /B ic ) IL 40 log (f ref /f ic ) TL ic f ref : base resonance frequency of reference case, calculated according to DIN-45673 f ic : base resonance frequency of isolated case, calculated according to DIN-45673
Noise & Vibration measurements Transmission Loss vs Insertion Loss Parameter Unit ML ref. CDM- TOMAS CDM-FSP C dyn.eq lbf/in 154,000 97,000 107,350 Total Mass lb 992 3,086 7,433 f res (DIN- f res 45673) Hz 39.0 17.5 11.9 I L @63Hz dbv -8.3-22.3-29.0 Calculated correction factor dbv - 13.9 20.6 Estimated T E L dbv - 36.2 49.6 T L E 40 log (f ref /f ic ) IL ic Measured T M dbv - 32.0 45.0 L T E L vs T M L % - 12.0 9.0
Noise & Vibration measurements Vibration levels in the buildings Residual vibration Vibration during train passage Vibration exceedence vs residual P 1 P 2 P 3 P 4 v rms (μin/s) v rms (μin/s) dbv (ref 1μin/s) 82.7 82.7 0.0 82.7 86.6 +0.4 74.8 106.3 +3.0 102.4 110.2 +0.6 Exterior vibration measurements results well within ML recommended limit of 393.7 μin/s
Summary and Conclusions The different FST systems were described in terms of their respective dynamic performance characteristics and engineering detailing for their implementation and maintainability. The different FST systems were selected based upon a performance based specification From the vibration measurements: Dynamic stiffness of the resilient materials is basis for prediction of isolation performance TL for passing train and mechanical impulse correlate well for f > 50 Hz For higher frequencies (f > 50 Hz), TL measurements allow an easy and cost-efficient reasonable estimation of the expected IL (preliminary quality assurance) Selected FST systems: Good correlation with predicted performance Effective in mitigating the vibration in surrounding buildings
Thank you for your attention! Patrick Carels CDM Novitec, President Evanston, IL www.cdm-novitec.com