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 and FL27 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 |
|
FL27 |
Monument |
Opposite to Shung Him Tong Public Toilet, at the
bottom of slope feature |
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 and FL27 |
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 HFL05, FL02, FL04, FL24, FL27 and FL36
under ND/2019/05 for EP-473/2013/A. As HFL05, FL04, FL24, FL27 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 and FL27 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.