8.1
In
accordance with the updated EM&A Manual, baseline condition survey and
baseline vibration impact assessment shall be conducted for identified built
heritage prior to the commencement of construction works. Baseline condition
survey and baseline vibration impact assessment shall be conducted by a
qualified building surveyor or qualified structural engineer to define the
vibration limit (a vibration limit at 7.5mm/s and 15mm/s could be adopted for
graded historical buildings and historical buildings respectively) and to
evaluate if construction vibration monitoring and structural strengthening
measures are required during construction phase to ensure the construction
performance meets the vibration standard stated in the EIA report.
8.2
According
to the condition survey report from cultural heritage condition survey for Fanling Bypass Eastern Section under EP-473/2013/A, a vibration monitoring plan was
proposed for the surveyed cultural heritage based on the Buildings Department’s
Practice Note (PNAP) APP-137. This section presents the results of built
heritage monitoring performed by the Contractor according to the proposed
monitoring plan in baseline condition survey report. Appendix B shows the Limit Levels for the monitoring works.
8.3
In
the reporting month, construction vibration monitoring was conducted for built heritage features at FL02 when pile driving operation
was conducted within assessment area of the construction works. The location of
the construction vibration monitoring stations was summarised
in Table 8.1 and shown in Appendix K.
Table 8.1 Location of Construction Vibration Monitoring
|
EP. No |
Contract No. |
Monitoring Station (s) |
Nature of Cultural Heritage |
Location (s) |
|
EP-473/2013/A |
ND/2019/05 |
FL02 |
Grave |
Northwest side of Shung
Him Tong Tsuen, at the hillside behind On Lok Garden |
Monitoring Parameters and Frequency
8.4
Table 8.2 summarises
the vibration monitoring plan for surveyed cultural heritage under the Works
Contracts. Vibration monitoring was conducted for surveyed built heritage when
pile driving operation was conducted within the assessment
area of construction works.
Table 8.2 Vibration Monitoring Plan
|
EP. No |
Contract No. |
Monitoring Stations |
Distance with Construction Works |
Monitoring Plan |
|
EP-473/2013/A |
ND/2019/05 |
FL02 |
Within 50m |
Daily assessment is required |
|
Within 75m |
Bi-daily assessment is required |
|||
|
Within 100m |
Weekly assessment is required |
Remark:
[1] Baseline condition survey was
conducted for built heritage features at HFL08, FL05, FL07, FL08, FL10, FL11,
FL17, FL19, FL31 and FL33 under ND/2019/04, also HFL05, FL02, FL04, FL24, FL27
and FL36 under ND/2019/05 for EP-473/2013/A. As HFL05, HFL08, FL04, FL05, FL07,
FL08, FL10, FL11, FL17, FL19, FL24, FL27, FL31, FL33 and FL36 were not within
the assessment area of the related construction work, no construction vibration
monitoring was conducted for the built heritage in the reporting month.
8.5
The
construction vibration monitoring was conducted throughout each event of the
pile driving operation on a daily basis. The effect of ground-borne vibration
from piling works on the surveyed built heritage was assessed by the maximum
peak particle velocity (ppv), which was obtained from
the maximum value of measurement of all pile driving operation events.
8.6
Copies of calibration certificates
of the monitoring equipment employed by the Contractor of the construction vibration
monitoring are attached in Appendix C.
8.7
In
the reporting month, construction vibration monitoring was carried out by the
Contractor for the built heritage features at FL02 on a daily basis when pile
driving operation was conducted within 50m of the construction work. No Limit Level
exceedance for construction vibration monitoring was recorded in the reporting
month. The monitoring results are provided in Appendix K.
8.8
Table 8.3 summarises
the vibration limits for construction vibration monitoring for surveyed cultural
heritage.
Table 8.3 Vibration Limits for
Construction Vibration Monitoring
|
Type of Building |
Guide Values of Maximum ppv*
(mm/Sec) |
|
|
Transient Vibration |
Continuous Vibration |
|
|
Vibration-sensitive
/ dilapidated buildings# |
7.5 |
3.0 |
|
Declared monuments/ Historical structures |
3.0 |
|
Remarks:
* peak
particle velocity
# as cultural heritages are sensitive receivers, vibration monitoring
should be classified as vibration-sensitive
8.9
If
any exceedance of limits is found or damage to either structural
or non-structural elements of the historic buildings is identified, the construction works
should be stopped
immediately and structural engineer’s advices should be sought for
any remedial work.