Background
The IT corridor of Pune metro is a 23 KM stretch of mixed geographic and demographic profile that connects residential concentration of Pune city to the IT office spaces. The Metro rail alignment of the entire 23 Kms has 23 stations with 3 stations specially identified for commercial development with shops and commercial outlets to be conceived in the concourse level.
The challenges and approach
As understood from the alignment survey, the issues of air-borne noise and ground borne vibrations were both of significance given the closer proximity and type of dwellings especially in the older part of Pune city; the ground borne vibrations were of particularly of concern in the IT corridor due to heights of the office buildings and their sensitivity to low frequency vibrations due to metro rail operations.
Considering the strata and bore log data and a desktop model of noise boundary conditions for the entire alignment of metro line, a comprehensive testing plan is worked out to determine Noise and Vibration data gathering procedure.
Site activities
Most of the international guidelines prescribe 24-hour continuous noise monitoring for establishing the background data, to be later used as a basis for superposing the actual noise data from the metro operations. Using the state-of-the-art autonomous type-1 noise data loggers, data were recorded from sensitive zones and relevant information were sieved.
Likewise, qualified force dropping rigs, vibration transmissibility tests were conducted at multiple strata sensitive zones considering buildings in the proximity and their ground coupling factors. The force energy loss through the connected ground mass is measured using high grade seismic grade sensors at fixed distances from the force drop location.
Noise and Vibration Test Setup at sensitive locations
In addition, the concourse commercial space area in 3 designated stations required a variety of tests and validations that included verification of structural response due to train operations, testing the concourse volume space for reverberation characteristics and also to understand the vibro-acoustic behaviour using volume velocity source.
FTA and RDSO compliance
The whole project is governed by strict audit processes and monitoring from the funding agencies; Noise & Vibration related activities were on a high scanner given that many of the international guidelines of Federal Transport Administration (FTA) and Research Design and Standards Organisation (RDSO) were to be followed all through the testing stage, data processing, calculations, modelling and results along with mitigation recommendations.
The comprehensive site activities of conducting multiple noise and vibration tests over the 23 KM stretch were accomplished in a tight schedule of 7 days requiring multiple agencies to co-ordinate the logistics and execution.
Results and reporting
This being a time bound task due to overall project delivery commitments, the exhaustive noise & vibration data recorded from the site were to be processed in a quick and organised way; the report contained results and inferences from testing, simulation and calculations combined with expert recommendations of passive and active plans to address noise and vibration issues on case-to-case basis.
Noise and Vibration modelling results
Task takeaway
From conducting site survey to preparing work flow plan to co-ordinating with multiple agencies for site help and preparations, data processing and submitting final report with very few iterations was all done in a record time of 30 days from start to end; the task and its deliverables met all the customer expectations and the target timelines for implementing the recommendations made by NV Dynamics. This task also re-affirmed our capability as a core noise and vibration services team with project management capability, technical competence and overall service delivery quality within the given time constraints.
This project and its experience will go a long way in how our maturity model has evolved and how it can be further utilised to handle larger and complex tasks.
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