Tunnel Boring Machine Noise Monitoring

BAM Ferrovial Kier Joint Venture

C300/410 Western Tunnels and Caverns

Tunnel Boring Machine Proactive Groundborne Noise and

Vibration Monitoring

February 2013

BAM Ferrovial Kier Joint Venutre - C300/410 Western Tunnels and Caverns Page 2 of 49 Tunnel Boring Machine Proactive Groudborne Noise an Vibration Monitoring 1391_TBM_Monitoring_Draft_Report_0-1_RPS 20 February 2013

Project C300/410 Western Tunnels and Caverns Tunnel Boring Machine Proactive Groundborne Noise and Vibration Monitoring

Report By Anderson Acoustics Limited 3 Trafalgar Mews 15-16 Trafalgar Street Brighton East Sussex BN1 4EZ www.andersonacoustics.co.uk T: 01273 696887

Client BAM Ferrovial Kier Joint Venture Site Office Great Western Road London W9 3NY

Date 20 February 2013

Project No 1391

Report Ref 1391_TBM_Monitoring_Draft_Report_0-1_RPS

Status Draft

Author(s) Richard Sullivan Principal Consultant BSc (Hons) MIOA Prannav Bhalla Senior Consultant MSc MIOA

20 February 2013

Reviewed Steve Summers Technical Director BSc (Hons) MIOA

20 February 2013

Approved Steve Summers Technical Director BSc (Hons) MIOA

20 February 2013

This document has been prepared using all reasonable skill and care. Anderson Acoustics Ltd accepts no responsibility or liability for any third party data presented in this report, or used for the basis of drawing any conclusions. This document is confidential to the named client above and Anderson Acoustics Ltd accepts no responsibility or liability resulting from third party use of this document or for a purpose other than for which it was commissioned. Anderson Acoustics accepts no responsibility for sound insulation tests indicating failure to comply with the requirements of the Building Regulations.


TABLE OF CONTENTS

1. INTRODUCTION .................................................................................................. 4

1.1 Purpose ................................................................................................................................... 4

2. WESTERN TUNNELS ............................................................................................. 5

2.1 Alignment ................................................................................................................................ 5

2.2 Tunnel Boring Machine ........................................................................................................... 5

3. MONITORING METHODOLOGY ................................................................................. 6

3.1 Monitoring Location 1: Basement Vaults of 13 Spring Street ................................................ 7

3.2 Monitoring Location 2: Sussex Square Basement Garage No. 20 ......................................... 10

3.3 Monitoring Locations 3: Sussex Square Gardens Surface Measurements ........................... 12

3.4 Calibration of Vibration Monitoring Equipment ................................................................... 15

4. ANALYSIS METHODOLOGY ..................................................................................... 16

4.1 Monitoring Location 1: Basement Vaults of 13 Spring Street .............................................. 17



5. RESULTS ......................................................................................................... 19

5.1 Monitoring Location 1: Basement Vaults of 13 Spring Street .............................................. 19

5.1.1 Five-minute Night-Time Ring Analysis ............................................................ 19

5.1.2 One-minute Consecutive Ring Analysis ........................................................... 19


5.2.1 Five-minute Analysis ................................................................................. 27




6. SUMMARY FINDINGS ............................................................................................ 40

7. CONCLUSIONS ................................................................................................... 42

APPENDIX A EQUIPMENT .......................................................................................... 43

A.1 Vibration Monitoring Equipment Specification .................................................................... 43

A.2 Vibration Field Calibration Results ........................................................................................ 45

APPENDIX B RESULTS .............................................................................................. 46

B.1 Location 1: Five-minute Night-Time Analysis Frequency Graphs ......................................... 46

B.1 Location 2: Five-minute Night-Time Analysis Frequency Graphs ......................................... 48


1. INTRODUCTION

Anderson Acoustics Limited has been commissioned by BAM Ferrovial Kier Joint Venture (Team BFK) to carry out proactive groundborne noise and vibration monitoring of the Westbound (Phyllis) Tunnel Boring Machine (TBM) operations. This factual report provides details of the monitoring exercise undertaken, results and findings.

1.1 Purpose

The purpose of the monitoring exercise was to undertake proactive monitoring of the TBM in order to better understand the potential impact from re-radiated noise to residential and sensitive commercial premises along the tunnel alignments. To establish the potential impact it has been considered necessary to understand not only the level of re-radiated noise but also the duration. The findings would be used to inform the reactive monitoring strategy and methodology, and provide the community liaison teams with sufficient information to appropriately inform occupants of residential and other noise sensitive properties along the alignment of any potential impact.


2. WESTERN TUNNELS

2.1 Alignment

The TBM for the Western Tunnel drives were launched at Royal Oak travelling East parallel with the Paddington Main Line before turning South crossing below the Main Line and Bishops Bridge Road. It then travelled the entire length of Eastbourne Terrace through the Paddington Station Box, crossing under Praed Street and on to Spring Street. The planned TBM tunnel alignment runs the length of Spring Street, crossing under Sussex Gardens, Bathurst Mews, Sussex Square (and Gardens), Stanhope Terrace, Brook Street and finally Bayswater Road before continuing on under Hyde Park and on to Farringdon. The tunnels will generally be constructed at approximately the same depth as London Undergrounds Central line, with the rail level being about 20 m to 25 m below street level. The tunnel is constructed approximately 15 m below street level at Spring Street travelling downwards to 20 m under Sussex Gardens and further down to 25 m at Sussex Square (and Gardens). When the tunnel crosses under Bayswater Road it levels off at 30 m below street level continuing at the same approximate level under Hyde Park till it reaches North Audley Street at 25 m and then travels upwards reaching 20 m under Duke Street and levels off at 18 m under Gilbert Street where it meets Bond Street Station at the same level.

2.2 Tunnel Boring Machine

The TBM cutting head is approximately 6 rings (approximately 9.6 m) ahead of the erector, i.e. the tunnel ring building unit of the TBM which corresponds to the ring numbers referenced by the TBM control room during the build cycle. The chainage references the exact location of the TBM head in metres (referenced from the start of the tunnel at Royal Oak Portal) during a shove. Pre-cast concrete tunnel segments are bolted together within the rear section of the TBM shield while the TBM is stationary. This is referred to as the build phase of the overall ring cycle in this report. Using hydraulic jacking the TBM pushes forward off the newly constructed tunnel ring while the cutting head is rotating at approximately 2-3 rpm. The TBM advances forward very slowly pushing the newly constructed ring out of the rear of the shield. The ring in fact stays still but the TBM shield moves forward to reveal the newly constructed ring. Once the TBM has advanced forward one ring width, approximately 1.6 metres, the jacks stop pushing and the cutting head stops rotating. This is referred to as the shove phase of the overall ring cycle in this report. At this point the cycle starts again with the next ring being bolted together within the shield and the process continues.


3. MONITORING METHODOLOGY

Three sites were identified as suitable locations for the proactive monitoring exercise, as follows:

1. Basement Vaults of 13 Spring Street; 2. Basement Garage (no. 20) of 31-51 Sussex; and 3. Sussex Square Gardens.

The monitoring locations are shown in Figure 3.1. Locations 1 and 2 were inside basement areas of buildings above the tunnel alignment to enable both vibration and re-radiated noise monitoring. Location 3 was outside in the private gardens of Sussex Square. This only enabled vibration monitoring, however, this was free from interference from building structures and also provided the opportunity for monitoring at two positions simultaneously, location 3A and 3B. Monitoring was undertaken using continuous data recording equipment for both vibration and sound to allow for post processing of the results and the flexibility this brings. Further details on the monitoring equipment used and the reasons for choosing the monitoring locations are provided in the following Sections 3.1 to 3.3. Figure 3.1: Monitoring Locations

Monitoring Location 3A

Monitoring Location 1


Monitoring Location 3B


3.1 Monitoring Location 1: Basement Vaults of 13 Spring Street

The monitoring position was located in the basement vaults of kall kwik print shop at 13 Spring Street above Ring 719 (head chainage 1657) of the tunnel alignment, as shown in Figures 3.2 and 3.3. The basement floor was measured to be approximately 3 m below street level and extended out under the road and pavement of Spring Street putting it directly above the westbound tunnel. Location 1 was selected for the following reasons:

Directly over the tunnel alignment and at a depth shallower (at approx. 14 m) than further along the alignment, which was considered to provide a worst case scenario and in turn cleaner data due to the likely higher vibration and re-radiated noise (if any) measured;

To refine the monitoring methodology before undertaking locations 2 and 3 which would be the last and only opportunities before the TBM entered Hyde Park;

Unoccupied basement vault where the monitoring equipment could be left unattended with minimal interference from footfall and other extraneous sources of noise and vibration from within the premises, compared to other locations on Spring Street;

Permission given by the building occupants to access the monitoring location as and when required during the normal opening hours of the premises, which was necessary in order to change batteries and memory cards every 2 to 3 days, and also for attended monitoring when the TBM was directly below the location (during the day);

To capture baseline data of pre-existing vibration sources whilst the TBM was not in operation which would assist in identifying the TBM shove events and enable comparison of the TBM operations against baseline levels;

Considered representative of the likely noise and vibration impact within similar masonry, but occupied, basement structures further along the tunnel alignment (except due to the room finishes and tunnel depth);

Provided sufficient distance from monitoring location 2 to capture the anticipated gradual increase and decrease in both vibration and re-radiated noise (if any) as the TBM moved towards and then passed the monitoring location which allowed the necessary time to demobilise, finalise monitoring methodology and mobilise in time for location 2.

Vibration monitoring at location 1 commenced at 16:30 hrs on Friday 19th October 2012 in order to capture baseline data whilst the TBM was stationary at Ring 669 (head chainage 1588.63). The TBM restarted tunnelling operations at 10:27 hrs on Monday 22nd October 2012 at Ring 669 (head chainage 1588.63). Baseline data was captured to create a benchmark for vibration levels without the contribution of the TBM in close vicinity of the monitoring location. A noise monitor was installed at 10:30 hrs on Wednesday 24th October 2012 to record continuous sound within the basement vault as the TBM neared the monitoring location. The TBM was at Ring 691 (head chainage 1623.71) when sound recording commenced. Sound was recorded in order to capture the re-radiated noise and noise levels experienced at the monitoring location. The TBM cutting head passed the monitoring location at approximately 03:00 hrs on Friday 26th October 2012 at a depth of approximately 14 m beneath the basement floor of the monitoring location. The noise and vibration monitoring continued until 12:47 hrs on Wednesday 31st October 2012 when the equipment was demobilised, during which time the TBM had progressed to Ring 761 (head chainage 1736.71).


The progression of the TBM cutting head during the monitoring at location 1 is shown in Figures 3.2 and 3.3. Figure 3.2: Plan View of Monitoring Location 1 and TBM Cutting Head/Shield Progress

Figure 3.3: Section View of Monitoring Location 1 and TBM Cutting Head/Shield Progress

Details of the monitoring equipment used at Location 1 (Unit A) are provided in Table 3.1. The specifications of the vibration monitoring equipment can be found in Section A.1 of Appendix A. Table 3.1: Details of Monitoring Equipment at Location 1

Data Type Equipment Serial No.

Vibration (Unit A)

Rion DA-20 Data Recorder 10770816

3 x Rion PV-87 High Sensitivity Accelerometer X axis: 23754, Y axis: 23749, Z axis: 23753

Rion VP-80 3 ch. Charge Pre-amplifier 30400401

Rion VP-51A Microdot Cable (3 no.) N/A

DIN Standard Ground Plate N/A

Sound

Rion NL-52 with NX-42WR Sound Recording 00620960

Rion Microphone Class 1 UC-59 03878

Rion EC-04 2 m Microphone Extension Cable N/A

Rion WS-15 IEC 61672 Class 1 Outdoor Windshield

N/A

Monitoring Location 1 TBM cutting head at start of vibration monitoring

TBM cutting head at end of vibration monitoring


TBM cutting head at end of vibration monitoring

TBM cutting head at start of vibration monitoring

TBM cutting head at start of sound monitoring

TBM cutting head at start of sound monitoring


Vibration monitoring was undertaken using the 4-channel Rion DA-20 data recorder connected to the three Rion PV-87 high sensitivity accelerometers via the microdot cables and charge pre-amplifier. This equipment enabled continuous acceleration WAV file recording in the X, Y and Z axes suitable for post processing purposes. The upper frequency cut-off on the data recorder was set to 500 Hz with a sample frequency multiple of 2.56. This allowed for 3 days of monitoring data on the internal 2 GB compact flash memory card which was necessary in order maintain continuous monitoring over the weekend periods when access to the basement was not possible. The data recorder was powered primarily by two external 6V, 12Ah batteries with 4 internal LR6 AA backup batteries all stored securely in a weatherproof Pelicase. The three accelerometers were mounted to three sides of a metal 40mm cube to provide monitoring of X, Y and Z axes and the cube was then mounted to the ground plate which had been manufactured to meet the German DIN Standard DIN 45669-2. The ground plate was positioned towards the centre of the basement vault floor and levelled using the three spikes. The ground plate/accelerometers were orientated as accurately as possible so that the Y-axis ran parallel with the tunnel alignment and the X-axis ran perpendicular. The internal sensitivity values were set for each axis as per the provided laboratory calibration certificates and the dynamic range was set to 0.01 V, which provided the lowest range. The field calibration of the vibration monitoring system was later checked using a Svan SV-111, see Section 3.4 for further details. The memory cards and external batteries were changed every 2-3 days to ensure continuous monitoring. Re-radiated noise monitoring was undertaken using the Rion NL-52 sound level meter with sound recording option installed. The microphone was housed within the outdoor windshield to provided additional protection within the damp basement vault and connected to the sound level meter, which was stored securely in a weatherproof Pelicase, using the 2 m extension cable. The microphone was mounted vertically on a pole at 1.5 m above floor level towards the centre of the basement vault. The sound level meter was configured to store continuous WAV file sound recording from 20 Hz to 20 kHz at 16 bits with a sampling frequency of 24 kHz, suitable for post processing purposes. This allowed for 3 days of monitoring data on the internal 16 GB Secure Digital memory card which was necessary in order to maintain continuous monitoring over the weekend periods when access to the basement was not possible. The dynamic range on the sound level meter was set at 20 to 90 dB. The field calibration of the sound level meter was undertaken immediately before and after monitoring, including when the monitor was stopped and started again in order to change memory cards and external batteries, which took place every 2-3 days to ensure continuous monitoring. During the monitoring period a field calibration drift between 0.1 to -0.1 dB was noted which is within the acceptable range of deviation. Before monitoring commenced the clocks on all equipment were synced as accurately as possible to the telephone talking clock. During the monitoring period at location 1, the clocks in the UK went back on Sunday 28th October 2012 by 1 hour. The clocks on the equipment were not adjusted and remained on British Summer Time. On Friday 26th October 2012 between approximately 09:30 and 12:00 hrs, when the TBM was directly below the monitoring location, the monitoring equipment was attended and a second Rion NL-52 was used to provide real time frequency and time level information on the vibration data being recorded using the Monitor output on the Rion DA-20 data recorder. A photograph of the noise and vibration monitoring equipment as setup at location 1 is shown below in Figure 3.4.


Figure 3.4: Equipment Setup at Monitoring Location 1

3.2 Monitoring Location 2: Sussex Square Basement Garage No. 20

The monitoring position was located in garage no. 20 in the basement area of 31-51 Sussex Square above Ring 840 (chainage 1854) of the tunnel alignment, as shown in Figures 3.5 and 3.6. The basement garage floor was measured to be approximately 2.5 m below street. Garage no. 20 is approximately 4.7 metres horizontally from the centre of the tunnel alignment. Location 2 was selected for the following reasons:

Near to the tunnel alignment, with the tunnel within the range of typical depth (at approx. 22 m), which was considered to provide a comparable monitoring scenario to that expected for the majority of the proposed alignment;

Unused garage (no. 20) and relatively quiet garage area where the monitoring equipment could be left unattended with minimal interference from extraneous sources of noise and vibration compared to other locations within the surrounding area;

Permission given by the building management to access the monitoring location as and when required during Porter hours 7 days per week, which was necessary in order to change batteries and memory cards every 2 to 3 days, and also for attended monitoring when the TBM was at its nearest point (during Porter hours);

Considered representative of the noise and vibration impact likely within the basement area of similar steel/concrete framed large apartment buildings further along the tunnel alignment (except due to the room finishes);

Noise and vibration monitoring at location 2 commenced at 20:00 hrs on Monday 5th November 2012 whilst the TBM was in operation at Ring 811 (head chainage 1815.54). The TBM cutting head passed the monitoring location at approximately 15:40 hrs on Friday 9th November 2012 at a depth of approximately 20.3 m below the floor level of the basement garages.

3 x Accelerometer

on DIN Plate

Microphone in

Outdoor Windshield


The noise and vibration monitoring continued until 10:38 hrs on Monday 12th November 2012 when the equipment was demobilised, during which time the TBM had progressed to Ring 871 (head chainage 1911.52). The equipment was removed to be used at location 3. The progression of the TBM cutting head during the monitoring at location 2 is shown in Figures 3.5 and 3.6. Figure 3.5: Plan View of Monitoring Location 2 and TBM Cutting Head/Shield Progress

Figure 3.6: Section View of Monitoring Location 2 and TBM Cutting Head/Shield Progress

The same monitoring equipment was used at location 2 to that at location 1. As before, details of the monitoring equipment are provided in Table 3.1. The configuration of the equipment and placement of the microphone and accelerometers were identical to that employed at location 1. Furthermore, there was no significant drift in field calibration observed for the sound level meter. See Section 3.4 regarding the field calibration of the vibration monitoring equipment. A malfunction with the sound level meter was noted on Friday 9th November 2012 at approximately 14:00 hrs which had caused the meter to freeze and as a result sound recording and noise data between 00:18 on Thursday 8th November 2012 and 14:13 hrs on Friday 9th November 2012 was lost. A reboot of the sound level meter rectified the software problem enabling sound recording to recommence. On Friday 9th November 2012 between approximately 10:00 and 13:30 hrs, when the TBM was directly below the monitoring location, the monitoring equipment was attended and a second Rion NL-52 was used to provide real time frequency and time level information on the vibration data being recorded using the Monitor output on the Rion DA-20 data recorder. A photograph of the noise and vibration monitoring equipment as setup at location 2 is shown below in Figure 3.7.


TBM cutting head at start of monitoring

TBM cutting head at end of monitoring





Figure 3.7: Equipment Setup at Monitoring Location 2

3.3 Monitoring Locations 3: Sussex Square Gardens Surface Measurements

Attended monitoring was undertaken at surface level in the private gardens at Sussex Square at two positions, location 3A and 3B, as shown in Figures 3.8 and 3.9. Location 3A was sited directly above the Westbound tunnel alignment at approximately Ring 888. Location 3B was sited perpendicular to Ring 885 of the Westbound tunnel alignment, approximately 20 m horizontally. Location 3 was selected for the following reasons:

To obtain clean vibration monitoring data free from building structures and the specific inherent interference structures have on data;

Enabled two locations as an array approximately 20 m apart which could be used to verify the expected outcome that vibration levels are greatest directly above the TBM alignment;

Considered to be a quieter location for surface monitoring for both noise and vibration due to greater distances from London Underground lines and major roads, compared to locations within Hyde Park which had also been considered a possible monitoring location;

Tunnel alignment within the typical range depth at approximately 25 m below the surface level.

Attended vibration monitoring at locations 3A and 3B was undertaken between 01:42 and 06:31 hrs on Tuesday 13th November 2012 during which the TBM progressed from Ring 884 (head chainage 1930.64) through 887 (head chainage 1937.07). At the start of the monitoring the TBM cutting head was approximately 1 metre ahead of location 3A at a depth of approximately 25 m below the surface level of the gardens. The progression of the TBM cutting head during the monitoring at location 3A and 3B is shown in Figures 3.8 and 3.9.

3 x Accelerometer

on DIN Plate

Microphone in

Outdoor Windshield


Figure 3.8: Plan View of Monitoring Locations 3A and 3B and TBM Cutting Head Progress

Figure 3.9: Section View of Monitoring Location 3A and 3B and TBM Cutting Head Progress

Details of the monitoring equipment used at Locations 3A (Unit A) and 3B (Unit B) are provided in Table 3.2. Table 3.2: Details of Monitoring Equipment at Locations 3A and 3B

Data Type Equipment Serial No.

Vibration Location 3A (Unit A)





300 mm Steel Angle Ground Spike N/A

Vibration Location 3B (Unit B)





300 mm Steel Angle Ground Spike N/A



Monitoring Location 3A Monitoring Location 3B


TBM cutting head at end of monitoring Monitoring Location 3A

Monitoring Location 3B


The monitoring equipment used at location 3A was the same as that used at locations 1 and 2. An additional, but identical vibration system was used at location 3B. Both systems were configured as previously used at locations 1 and 2, with the exception of the upper frequency cut-off which was increased from 500 Hz to 1000 Hz and the replacement of the ground plate with steel angle ground spikes. The duration of the attended monitoring at location 3 meant that the changing of memory cards and batteries were not required allowing for continuous vibration monitoring from start to finish. See Section 3.4 regarding the field calibration of the vibration monitoring equipment. Trilateration was employed in order to position location 3A directly above the tunnel alignment by using landmarks within the gardens that were also marked on a supplied CAD drawing of the tunnel alignment. Location 3B was sited approximately 20 m perpendicular to the tunnel alignment from location 3A. Photographs of the vibration monitoring equipment as setup at location 3A and 3B are shown below in Figures 3.10 and 3.11. Figure 3.10: Equipment Setup at Monitoring Location 3A

Figure 3.11: Equipment Setup at Monitoring Location 3B

3 x Accelerometer

on Ground Spike

3 x Accelerometer

on Ground Spike


3.4 Calibration of Vibration Monitoring Equipment

Field calibration of the two vibration monitoring systems (Rion DA-20 data recorder + VP-80 charge pre-amplifier + 3 x VP-51A microdot cables + 3 x PV-87 accelerometers) was undertaken using a Svantek SV-111 Vibration Calibrator (serial no. 25074) across three base frequencies, 15.92 Hz, 79.82 Hz and 159.2 Hz for all three axes. Since only the Z-axis has been analysed and reported in this document, only the field calibration results for the Z-axis have been reproduced in Table A.1 of Appendix A. The average frequency error percentage for the Z-axis was 0.09 % for Unit A and 0.1 % for Unit B. The average amplitude error percentage for the Z-axis was 5.98 % for Unit A and 4.66 % for Unit B. This is considered to be within the acceptable deviation for the type of monitoring equipment.


4. ANALYSIS METHODOLOGY

The results of the vibration and re-radiated noise monitoring has been analysed using both the Rion DA-40 Viewer software and Prosig DATS-lite data analysis software. Although acceleration levels in mm/s2 were measured in three axes (X, Y and Z), initial analysis showed that the Z-axis provided the best correlation between measured vibration and measured re-radiated noise, and as result only the Z-axis data has been analyzed in detail and presented in this report. It is generally considered that the resultant re-radiated noise is proportional to the vibration velocity levels in mm/s. It has therefore been necessary to convert the vibration acceleration levels measured by the monitoring equipment to vibration velocity using the Prosig DATS-lite software. A template project was created in the Prosig DATS-lite software in order to process multiple files in exactly the same way. While it is not universally accepted, decibel notation is in common use for vibration. In this report vibration velocity is provided in decibels (dB) using a reference vibration velocity of 1x10-6 mm/s. As standard, re-radiated noise is provided in dB using a reference sound pressure level of 2x10-5

pascals. A number of published papers and text books were reviewed during the initial analysis in order to finalise an appropriate methodology for detailed data analysis. One paper in particular, published on the Transportation Research Boards website on TCRP Web-Only Document 48: Ground-Borne Noise and Vibration in Buildings Caused by Rail Transit states A-weighting is relevant because current standards for ground-borne noise are typically expressed in terms of the indoor A-weighted sound level. It is commonly assumed that the sound pressure level inside a room is proportional to the vibration velocity level of the vibrating room surfaces. Therefore, A-weighted vibration velocity should also be a relatively good predictor of A-weighted ground-borne noise. This was further confirmed by the initial analysis of the measured vibration velocity level and re-radiated noise level that seemingly supports this assumption. As a result, A-weighted filters have been adopted for the analysis methodology for both noise and vibration. Noise and vibration data was analysed in one-third octave band centre frequencies over the range of 20 to 500 Hz. To obtain single figure values, the data was A-weighted to account for the relative loudness perceived by the human ear. It should also be noted that frequency data presented in the numerous graphs in this report have been A-weighted to assist in visualising the perceived noise levels. Noise and vibration data was analysed during TBM shove events ranging from 23rd October 2012 at location 1 to 13th November 2012 at location 3. The duration of each analysed shove event varied from 31 to 200 minutes. Initial analysis of the vibration monitoring data was attempted on a few complete shove events, however due to the irregular stop/start patterns of the TBM as well frequent interference from extraneous vibration sources, such as London Underground trains, road traffic and pedestrians, this method proved to be difficult. To avoid the complication resulting from the stop/start pattern, a shorter sample period of five-minute was chosen of the operating TBM during shove events. However, even at only five-minutes it was still only possible to obtain sufficient clean data during night-time hours when the London Underground trains had stopped operating for vibration only. Although providing a high level understanding of the build-up and drop-off of vibration velocity levels during the TBM pass-by, it proved insufficient for a comparison of vibration levels against re-radiated noise levels as the sample TBM events were limited to approximately one per day, which provided only one or two nights events when re-radiated noise was actually audible.


This led on to an even shorter sample period of one-minute being chosen for analysis of the TBM during shove events. One-minute periods enabled comparison between simultaneous vibration and re-radiated noise levels without the complication of the stop/start pattern of the TBM and also with significantly less interference from extraneous noise and vibration sources, as previously discussed. Technical data from the TBM control room was imported into a spreadsheet so that the clock time, advance distance (mm) and cutting wheel rotation speed (approximately 2-3 rpm) could be analysed. The clock time was then offset to allow for the difference in internal clock time between the TBM and the noise and vibration monitoring equipment. This was done by comparing the cutting wheel rotation speed data with the recorded noise and vibration data. The one and five-minute samples were cut from larger data sets using the Rion DA-40 Viewer software and then passed through the pre-configured Prosig DATS-Lite project as detailed above. The analysed noise and vibration samples of the TBM shove events could not be corrected for background sources due to the inability to locate baseline samples that were representative across all frequencies of that present in the TBM shove events. Instead, the influence from background sources were minimised by careful selection of the TBM shove events.


Five-minute night-time analysis Initial analysis was carried out for data from seven consecutive nights during periods of low ambient noise and vibration. The ring build numbers were 676, 689, 702, 712, 725, 737 and 747. Data was analysed for a five-minute period during which noise and vibration levels were considered to be most representative of the TBM and least affected by extraneous sources. Baseline data has not been presented for the five-minute analysis periods as suitable baseline data, not contaminated by any extraneous sources, was not found.

One-minute consecutive ring analysis Further analysis was carried out for data from the shove cycle of 24 consecutive rings. The ring build numbers were 702 to 725. Data was analysed for a one-minute period during which noise and vibration levels were considered to be most representative of the TBM and least affected by extraneous sources. Contamination from extraneous sources was particularly high during the daytime so it was not considered practicable to analyse periods greater than one-minute for this comparative analysis. Baseline noise and vibration levels were also analysed for a one-minute period. This data was taken from a representative sample before or after each shove event while the TBM head was stationary.


Five-minute night-time analysis

Initial analysis was carried out for data from six consecutive nights during periods of low ambient noise and vibration. The ring build numbers were 815, 826, 830, 840, 852 and 864. Data was analysed for a five-minute period during which noise and vibration levels were considered to be most representative of the TBM and least affected by extraneous sources.

Baseline data has not been presented for the five-minute analysis periods as suitable baseline data, not contaminated by any extraneous sources, was not found.


One-minute consecutive ring analysis

Further analysis was carried out for data from the shove cycle of 25 consecutive rings. The ring build numbers were 823 to 847. Data was analysed for a one-minute period during which noise and vibration levels were considered to be most representative of the TBM and least affected by extraneous sources. Contamination from extraneous sources was particularly high during the daytime so it was not considered practicable to analyse periods greater than one-minute for this comparative analysis. No re-radiated noise data was available for seven of the rings in this analysis (828 to 834) due to a software malfunction with the noise monitor. Baseline noise and vibration levels were also analysed for a one-minute period. This data was taken from a representative sample before or after the shove event while the TBM head was stationary.


One-minute consecutive ring analysis

Analysis was carried out for data from the shove cycle of four consecutive rings at two monitoring locations 3A and 3B. The ring build numbers were 884 to 887. For the same reasons as detailed above, data was analysed for one-minute periods during which vibration and re-radiated noise levels were considered to be most representative of the TBM and least affected by extraneous sources. Baseline noise and vibration levels were also analysed for a one-minute period. This data was taken from a representative sample before or after the shove event while the TBM head was stationary.


5. RESULTS

The analysis of the TBM shove events detailed in Section 4 of this report was carried out over five-minute and one-minute periods. The results and analytical discussions are presented below.


5.1.1 Five-minute Night-Time Ring Analysis Figure 5.1 details the overall A-weighted vibration velocity levels across seven consecutive nights from Tuesday 23rd October 2012 to Monday 29th October 2012. Ring build number 712 (head chainage 1656.97) coincides approximately with the TBM cutting head being directly underneath the monitoring location which would account for the highest vibration velocity levels measured at this location, based on the 5 minute samples analysed. This figure clearly demonstrates the expected build-up and drop-off of the vibration velocity levels as the TBM passed by the monitoring location. Five-minute analysis of re-radiated noise levels have not been included due to the samples being contaminated from various extraneous sources, in addition to their only being one or two night-time 5 minute samples where the re-radiated noise is actually audible. Figure 5.1: TBM Shove Event Velocity Levels for Ring Build Numbers 676, 689, 702, 712, 725, 737 and 747

Note: Horizontal distance from monitoring location to TBM cutting head provided above in metres.

A-weighted one-third octave band centre frequency graphs are provided in Section B.1 of Appendix B for each of the TBM shove events presented in Figure 5.1.

5.1.2 One-minute Consecutive Ring Analysis Figure 5.2 details the overall A-weighted vibration velocity levels of each TBM shove event alongside the A-weighted vibration velocity baseline levels across 24 consecutive ring build numbers 702 to 725. Ring build numbers 712 and 713 (head chainage 1656.97 to 1658.40) coincides approximately with the TBM cutting head being directly underneath the monitoring location which would account for the highest vibration levels measured at this location. This figure clearly demonstrates the expected build-up and drop-off of the vibration velocity levels as the TBM passed by the monitoring location.

0

10

20

30

40

50

60

70

676

689

702

712

725

737

747

Velo

cit

y L

evel in

dB(A

)

Ring Number

TBM ShoveBased on 5 minute samples

-58.5

7 m

-36.9

3 m

-16.5

8 m

0.0

0 m

+20.0

5 m

+39.1

4 m

+54.8

6 m


Figure 5.3 presents the overall A-weighted noise levels with the A-weighted baseline levels across 24 consecutive ring build numbers (702 to 725). The night-time low ambient noise and vibrations levels would be the reason for the level difference between the measured source noise and vibration data and baseline noise and vibration data. For Ring build numbers 702, 703, 712, 713 and 725 low baseline noise and vibration levels were measured as these events occurred during night-time hours when the contribution of extraneous noise and vibration sources were significantly reduced. These TBM shove events are therefore considered to be less contaminated. Figure 5.2: TBM Shove Event and Baseline Velocity Levels for Ring Build Numbers 702 to 725

Note: Horizontal distance from monitoring location to TBM cutting head indicated above in metres.

Figure 5.3: TBM Shove Event and Baseline Noise Levels for Ring Build Numbers 702 to 725


Table 5.1 details the numerical values of the one-minute noise and vibration single figure A-weighted levels.

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702

703

704

705

706

707

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719

720

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Table 5.1: TBM Shove Events and Baseline Noise and Vibration Overall Levels for Ring Build Numbers 702 to 725

Ring Number

TBM Head

Chainage

Horizontal Distance

m

TBM Shove Event Baseline Audible on

Event Sample

Noise Level dB(A)

Vibration Velocity

Level dB(A)

Noise Level dB(A)

Vibration Velocity

Level dB(A)

702 1639.81 -17.16 26.0 45.6 22.5 24.8 No

703 1642.13 -14.84 31.3 47.0 26.5 28.8 No

704 1643.57 -13.40 34.1 50.0 29.2 46.2 No

705 1644.73 -12.24 34.0 51.1 33.0 47.6 No

706 1646.73 -10.24 35.6 50.6 33.1 47.9 No

707 1648.97 -8.00 33.2 53.3 32.6 47.9 No

708 1650.67 -6.30 34.4 53.7 35.3 47.8 No

709 1651.37 -5.61 31.8 55.0 30.8 44.2 No

710 1654.05 -2.92 30.3 55.5 31.4 48.3 No

711 1655.30 -1.67 33.7 53.1 25.3 42.8 Yes

712 1656.97 0.00 32.2 58.5 22.4 26.6 Yes

713 1658.40 +1.43 32.2 59.7 23.3 26.9 Yes

714 1659.41 +2.43 36.3 57.2 34.4 52.3 Yes

715 1660.41 +3.44 35.1 57.3 36.1 46.8 No

716 1662.17 +5.19 40.4 58.2 37.3 55.9 Yes

717 1664.11 +7.14 34.2 56.5 33.0 46.9 Yes

718 1666.34 +9.37 33.5 55.4 34.9 48.9 No

719 1667.14 +10.17 36.2 56.7 31.7 50.6 Yes

720 1669.61 +12.64 40.0 53.3 32.3 50.7 Yes

721 1671.51 +14.54 37.0 52.1 31.4 45.7 Yes

722 1672.54 +15.57 33.9 52.5 31.5 44.3 Yes

723 1673.35 +16.38 33.8 50.8 30.2 47.0 Yes

724 1675.85 +18.87 26.9 45.5 28.5 40.8 No

725 1677.05 +20.08 29.5 44.2 24.8 28.4 No

The build-up and drop-off of the vibration velocity levels can be seen above in Table 5.1 with respect to the distance, i.e. the closer the TBM cutting head is to the monitoring location the higher the measured vibration velocity levels. It appears that the highest vibration levels are experienced when the cutting head is directly below the monitoring location, as originally expected, with the highest vibration velocity at approximately 60 dB(A). The TBM was audible as re-radiated noise within the receptor room when the TBM was approximately 1.67 m away horizontally (on the approach to the monitoring location) at Ring build number 711 (head chainage 1655.30). Re-radiated noise from the TBM continued to be audible until approximately 16.38 m horizontally passed the monitoring location at Ring build number 723 (head chainage 1673.35). The highest noise levels were measured when the TBM cutting head was approximately 5.19 m passed the monitoring location, with the highest noise level at approximately 40 dB(A). This puts the main shield behind the TBM cutting head directly below the monitoring location. It was noted whilst on site when the TBM was directly below the monitoring location that the re-radiated noise had a higher than expected frequency characteristics and tonal component. It quickly became apparent that the re-radiated noise (at least the dominant frequency components)


was not due to the vibration caused by the interaction between the TBM cutting head turning at 2-3 RPM and the ground/soil. It appeared to be originating from fast rotating plant on the TBM due to the higher frequency content of the noise. Upon further onsite investigation using the attended Rion NL-52, the dominant frequency content was noted to be around 400 Hz. Later discussions with the TBM team at Westbourne Park about the possible source of the tonal noise, it was suggested that it may be due to the 12 x 3000 RPM drive motors that power the TBM cutting head. Further analysis of the TBM log data against the measured noise and vibration levels appear to further support this. Figures 5.4 to 5.27 detail the A-weighted one-third octave band centre frequency vibration velocity and noise levels of the measured one-minute sample TBM shove events. The A-weighted noise and vibration baseline levels have also been included in the graph below for comparison with the measured TBM shove event levels. Figure 5.4: Ring 702, Head Chainage 1639.81 m Figure 5.5: Ring 703, Head Chainage 1642.13 m

Figure 5.6: Ring 704, Head Chainage 1643.57 m Figure 5.7: Ring 705, Head Chainage 1644.73 m

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1/3 Octave Band Centre Frequency (Hz)

Horizontal Distance -17.16 m

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Horizontal Distance +1.43 m

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The graphs clearly show an increase in vibration velocity levels over the baseline levels in the 250 to 500 Hz frequency range, with a dominant frequency of 400 Hz. When the TBM head/shield is close to the monitoring location there is a clear increase across all presented frequencies. However, typically the spectrum shape is similar between TBM shove event samples and baseline samples up to 200 Hz. Above 200 Hz there is a clear change in spectrum shape. It would appear that the measurement environment (ground, structures, room finishes etc) is dictating the spectrum shape below 200 Hz (not the level) whereas above it is dictated by the forced vibration from the TBM plant source. When the TBM shove event is audible on the samples this is shown by an increase in frequency content above 200 Hz. Differences between the measured noise levels during TBM shove events and baseline samples below 200 Hz are not understood to be due to the presence of the TBM, but instead due to the ever changing baseline. Table 5.2 details the numerical values of the one-minute noise and vibration 400Hz one-third octave band centre frequency (A-weighted) levels. As the 400 Hz component seems to be the dominant frequency for both noise and vibration it has been considered appropriate to provide a direct comparison of the noise and vibration levels at this frequency, as the single figure values provided in Table 5.1 on occasion are skewed by extraneous sources.

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Table 5.2: TBM Shove Event and Baseline Noise and Vibration 400 Hz 1/3 Octave Band (A-weighted) Levels for Ring Build Numbers 702 to 725

Ring Build

Number

TBM Head Chainage

Horizontal Distance

m

TBM Shove Event Baseline

Noise Level 400 Hz dB(A)

Vibration Velocity Level 400Hz dB(A)


Vibration Velocity Level 400 Hz dB(A)

702 1639.81 -17.16 22.1 38.1 14.0 15.2

703 1642.13 -14.84 24.9 32.2 20.3 15.7

704 1643.57 -13.40 26.9 42.0 21.3 21.9

705 1644.73 -12.24 27.2 36.9 25.1 23.7

706 1646.73 -10.24 29.5 46.1 25.5 29.0

707 1648.97 -8.00 25.4 37.0 24.0 31.5

708 1650.67 -6.30 28.9 48.0 28.7 30.8

709 1651.37 -5.61 25.7 51.6 23.1 21.6

710 1654.05 -2.92 23.3 47.6 23.8 27.6

711 1655.30 -1.67 26.4 47.8 18.3 25.1

712 1656.97 0.00 30.5 57.5 14.0 16.3

713 1658.40 +1.43 29.5 58.7 15.2 16.9

714 1659.41 +2.43 32.7 53.6 27.8 32.7

715 1660.41 +3.44 28.0 50.2 28.1 27.5

716 1662.17 +5.19 38.8 56.9 29.6 47.9

717 1664.11 +7.14 29.6 36.4 25.1 28.2

718 1666.34 +9.37 23.9 47.5 28.2 34.2

719 1667.14 +10.17 30.8 54.1 23.9 26.5

720 1669.61 +12.64 34.2 44.0 24.4 32.7

721 1671.51 +14.54 30.5 41.4 23.9 22.4

722 1672.54 +15.57 28.4 44.5 24.9 22.0

723 1673.35 +16.38 27.4 42.4 22.3 28.9

724 1675.85 +18.87 19.3 35.8 21.8 25.9

725 1677.05 +20.08 20.9 37.7 16.7 16.3

As shown in Table 5.1, the build-up and drop-off of the vibration velocity levels can be seen above in Table 5.2 also, with respect to the distance to and from the monitoring location. It appears that the highest vibration levels at 400 Hz are experienced when the cutting head is directly below the monitoring location as also noted from Table 5.1, as originally expected, with the highest vibration velocity at approximately 59 dB(A). The highest noise levels at 400 Hz were measured when the TBM cutting head was approximately 5.19 m passed the monitoring location as also noted from Table 5.1, with the highest noise level at approximately 39 dB(A). As before, this puts the main shield behind the TBM cutting head directly below the monitoring location.


5.2.1 Five-minute Analysis Figure 5.28 details the overall A-weighted vibration velocity levels across six consecutive nights from Tuesday 6th November 2012 to Monday 12th November 2012 (excluding Thursday 8th November 2012 as the TBM did not operate).


Ring build numbers 830 to 840 (head chainage 1845.73 to 1861.41) coincides approximately with the TBM cutting head and shield directly underneath the monitoring location which would account for the highest vibration velocity levels measured at this location, based on the 5 minute samples analysed. As shown before in Section 5.1.1, this figure clearly demonstrates the expected build-up and drop-off of the vibration velocity levels as the TBM passed by the monitoring location. Five-minute analysis of re-radiated noise levels have not been included due to the samples being contaminated from various extraneous sources, in addition to their only being one or two night-time 5 minute samples where the re-radiated noise is actually audible. Figure 5.28: TBM Shove Event Velocity Levels for Ring Build Numbers 815, 826, 830, 840, 852 and 864


A-weighted one-third octave band centre frequency graphs are provided in Section B.2 of Appendix B for each of the TBM shove events presented in Figure 5.28.

5.2.2 One-minute Consecutive Ring Analysis Figure 5.29 details the overall A-weighted vibration velocity levels of each TBM shove event alongside the A-weighted vibration velocity baseline levels across 25 consecutive ring build numbers 823 to 846. Ring build numbers 830, 835 and 840 (head chainage 1845.73, 1853.49 and 1861.41) account for the highest vibration velocity levels measured at this location. Ring build numbers 835 to 840 coincide approximately with the TBM cutting head being directly underneath the monitoring location. As previously in Section 5.1.2, this figure clearly demonstrates the expected build-up and drop-off of the vibration velocity levels as the TBM passed by the monitoring location. Figure 5.30 presents the overall A-weighted noise levels with the A-weighted baseline levels across 25 consecutive ring build numbers 823 to 846. The night-time low ambient noise and vibrations level would be the reason for the level difference between the measured source noise and vibration data and baseline noise and vibration data. For Ring build numbers 825, 826, 830, 831, 839, 840 and 841 low baseline noise and vibration levels were measured as these events occurred during night-time hours when the contribution of extraneous noise and vibration sources were significantly reduced. These TBM shove events are therefore considered to be less contaminated.

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TBM ShoveBased on 5 minute samples

-32.8

8 m

-15.3

1 m

-9.0

8 m

+6.9

6 m

+26.0

9 m

+45.8

3 m


Due to a software malfunction sound data is not available from 00:18 hrs on Thursday 8th November 2012 to 14:13 hrs on Friday 9th November 2012 which coincides with Ring build numbers 828 to 834. Figure 5.29: TBM Shove Event and Baseline Velocity Levels for Ring Build Numbers 823 to 846


Figure 5.30: TBM Shove Event and Baseline Noise Levels for Ring Build Numbers 823 to 846


Table 5.3 details the numerical values of the one-minute noise and vibration single figure A-weighted levels.

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823

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823

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No sound data due to software malfunction

0 m

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Table 5.3: TBM Shove Events and Baseline Noise and Vibration Overall Levels for Ring Build Numbers 823 to 847

Ring Number

TBM Head

Chainage

Horizontal Distance

m

TBM Shove Event Baseline Audible on

Event Sample

Noise Level dB(A)

Vibration Velocity

Level dB(A)

Noise Level dB(A)

Vibration Velocity

Level dB(A)

823 1833.85 19.64 34.4 57.1 35.1 43.1 No

824 1835.70 17.79 33.3 55.3 31.8 35.3 No

825 1836.72 16.76 29.7 56.3 27.8 33.2 No

826 1838.55 14.94 29.3 50.9 27.2 25.8 No

827 1839.91 13.58 29.8 59.6 27.8 29.0 No

828 1842.26 11.23 - 59.7 - 36.1 -

829 1843.77 9.71 - 62.2 - 32.4 -

830 1845.73 7.76 - 66.2 - 28.9 -

831 1846.01 7.48 - 58.1 - 28.5 -

832 1848.20 5.29 - 58.2 - 35.9 -

833 1849.49 4.00 - 61.4 - 48.6 -

834 1851.63 1.85 - 60.6 - 42.7 -

835 1853.49 0.00 36.9 71.1 35.2 41.6 No

836 1854.29 0.80 36.0 61.9 35.3 55.4 No

837 1856.76 3.27 33.9 59.5 31.2 45.8 No

838 1858.47 4.99 34.9 66.0 29.5 39.3 Yes

839 1860.00 6.51 31.6 57.1 26.4 33.7 Yes

840 1861.41 7.93 34.9 80.3 24.8 30.6 Yes

841 1862.81 9.33 28.6 55.9 23.6 33.1 Yes

842 1863.95 10.47 33.0 59.6 31.6 26.4 No

843 1865.57 12.08 34.0 66.6 32.5 42.0 No

844 1868.09 14.61 36.5 60.1 35.7 50.6 No

845 1869.80 16.31 34.3 63.0 32.8 41.3 No

846 1871.19 17.70 35.2 67.2 34.6 47.0 No

847 1872.65 19.16 35.4 58.3 35.3 47.7 No

The build-up and drop-off of the vibration velocity levels can be seen above in Table 5.3 (similar to that seen in Table 5.1), with respect to the distance. In this case, it appears that the highest vibration level of approximately 80 dB(A) was experienced when the tail end of the main shield was directly below the monitoring location, followed by the next highest vibration velocity level of 71 dB(A) when the cutting head was directly below the monitoring location. The TBM was audible as re-radiated noise within the receptor room, but only at night when the baseline noise was below approximately 30 dB(A). This coincided when the TBM was approximately 4.99 to 9.33 m horizontally passed the monitoring location at Ring build numbers 838 to 841 (head chainage 1858.47 to 1861.41). The highest noise level from the TBM with minimal contribution from baseline of approximately 35 dB(A) was measured when the tail end of the TBM main shield was directly below the receptor room, with the TBM head approximately 7.93 m passed the monitoring location. Figures 5.31 to 5.55 detail the A-weighted one-third octave band centre frequency vibration velocity and noise levels of the measured one-minute sample TBM shove events. The A-weighted noise and vibration baseline levels have also been included in the graph below for comparison with the measured TBM shove event levels.





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Figure 5.55: Ring 847, Head Chainage 1872.65 m

The graphs clearly show an increase in vibration velocity levels over the baseline levels in the 100 to 500 Hz frequency range, which is a wider frequency range than experienced at location 1, with the dominant frequency of 400 Hz still present with an additional of another peak at 125 Hz. Both these peaks are present in the baseline levels; however it would appear that the presence of the TBM excites these frequencies increasing them in level. It would appear that the measurement environment is dictating the spectrum shape to a certain degree as seen previously at location 1. When the TBM shove event is audible on the samples this is shown by an increase in frequency content above approximately 100 Hz, which is similar to that experience with vibration. When the TBM shove event is not audible on the samples, the baseline level is shown to be approximately equal across all frequencies to the measured TBM shove event, which would confirm that no or minimal re-radiated noise is present. Table 5.4 details the numerical values of the one-minute noise and vibration 400Hz one-third octave band centre frequency (A-weighted) levels for the same reasons as previously presented for location 1. As shown in Tables 5.1 and 5.2 for location 1 and Table 5.3 for location 2, the build-up and drop-off of the vibration velocity levels can be seen below in Table 5.4 also, with respect to the distance to and from the monitoring location. The highest vibration velocity levels at 400 Hz are noted at the same approximate levels and location relative to the TBM head/shield as the overall A-weighted vibration velocity. The highest noise levels at 400 Hz were measured when the TBM cutting head was approximately 7.9 m passed the monitoring location as also noted from Table 5.3, with the highest noise level at approximately 32 dB(A). As before, this puts the tail end of the TBM main shield directly below the monitoring location.

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Table 5.4: TBM Shove Event and Baseline Noise and Vibration 400Hz 1/3 Octave Band (A-weighted) Levels for Ring Build Numbers 823 to 847

Ring Build

Number

TBM Head Chainage

Horizontal Distance

m

TBM Shove Event Baseline


Vibration Velocity Level 400Hz dB(A)


Vibration Velocity Level 400 Hz dB(A)

823 1833.85 19.64 24.9 56.1 25.7 35.3

824 1835.70 17.79 23.1 54.3 20.9 25.1

825 1836.72 16.76 22.1 55.5 18.4 31.7

826 1838.55 14.94 19.1 48.8 17.9 21.6

827 1839.91 13.58 20.6 56.5 17.7 22.0

828 1842.26 11.23 - 59.1 - 27.9

829 1843.77 9.71 - 61.9 - 26.0

830 1845.73 7.76 - 66.0 - 25.6

831 1846.01 7.48 - 56.9 - 25.8

832 1848.20 5.29 - 57.1 - 27.4

833 1849.49 4.00 - 60.8 - 43.8

834 1851.63 1.85 - 59.9 - 39.1

835 1853.49 0.00 28.3 70.9 25.9 36.5

836 1854.29 0.80 24.4 60.9 24.0 51.9

837 1856.76 3.27 27.9 58.8 19.7 40.0

838 1858.47 4.99 30.7 65.7 18.8 28.8

839 1860.00 6.51 23.8 55.3 17.0 29.4

840 1861.41 7.93 31.8 80.2 14.2 25.4

841 1862.81 9.33 20.4 53.9 14.1 30.1

842 1863.95 10.47 24.3 58.3 23.3 23.4

843 1865.57 12.08 24.7 66.2 23.7 32.2

844 1868.09 14.61 28.9 58.3 26.2 48.1

845 1869.80 16.31 24.0 62.3 22.9 35.1

846 1871.19 17.70 25.8 66.7 23.6 43.3

847 1872.65 19.16 25.5 57.1 25.1 42.0


5.3.1 One-minute Consecutive Ring Analysis Figure 5.56 and 5.57 detail the overall A-weighted vibration velocity levels of each TBM shove event alongside the A-weighted vibration velocity baseline levels across four consecutive ring build numbers 884 to 887, for location 3A and 3B respectively. The TBM cutting head had passed monitoring location 3A by approximately 1 m horizontally when monitoring commenced. The first ring build number 884 (head chainage 1931.25) measured provided the highest overall A-weighted vibration velocity level. As expected, as it TBM head moved further away from location 3A the vibration velocity level gradually reduced.


Figure 5.56: Location 3A - TBM Shove Event and Baseline Velocity Levels for Ring Build Numbers 884 to 887


A similar trend was noted for location 3B but due to the perpendicular distance of 20 m the change in total distance from the TBM head to the monitoring location was less significant

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Tunnel Boring Machine Noise Monitoring