080731 6LYG A1 Particular Tunnelling Specification ... - SCATnow

Lee Tunnel, Contract No. 6LYG/A1
PT – Particular Tunnelling Specification - PT200
PT241.8
PT241.9
limited to 5mm at the nearest Structure or identified Utility at Risk
PT241.10 Settlement monitoring points are to be established for the lengths of the tunnel.
Settlements monitoring reference arrays comprising three reference points,
centred on, and perpendicular to the tunnel line, are to be placed at 50m
maximum centres along the route of the tunnel. The transverse arrangement
should be matched to the predicted settlement trough. Monitoring is to be
undertaken to ensure the stability of readings prior to and after tunnelling has
been completed, and at intervals to identify any trends in readings that
demonstrate that ground movements are in accordance with predictions and
control of the stability of works. Monitoring shall be in the form of precise levelling
unless otherwise instructed by the Project Manager. Monitoring points shall be
established at least 200m in advance of the face and at least 3 No.
measurements undertaken to establish base readings. When the face has
passed the array readings shall be undertaken on a daily basis for 7 days.
Thereafter readings shall continue on a weekly basis for 4 weeks or until ground
movements have ceased or as directed by the Project Manager.
PT241.11 Settlement monitoring reference points shall comprise 50mm long masonry nails
in road pavements cast in protective concrete, or 10mm diameter 50mm long
stainless steel round head bolts with stainless steel washers with steel tamp in
anchors with lead sleeves in structures (Ref. to BRE Digest 386 Monitoring
building and ground movement by precise levelling). Settlement monitoring
reference points in verges and other non paved areas shall comprise >1.0m long
20mm diameter deformed steel bar driven into the ground encased in protective
concrete. If these systems are not acceptable to the owners of the land, other
systems are to be proposed by the Contractor for agreement by the Project
Manager and the relevant third parties.
PT241.12
PT241.13
Monitoring measurements are to be undertaken to an accuracy of +/-0.5mm.
All monitoring systems shall be removed at the end of the monitoring requirement
subject to the agreement of the Project Manager and relevant third party or their
agent.
PT241.14 Monitoring of settlement of the Network Rail running rails and other infrastructure
will be carried out by a surveyor approved by Network Rail. The arrangement of
the installation of the targets on the tracks and ancillary structures is being
agreed with Network Rail by the Employer as will the frequency of monitoring and
reporting. The Contractor shall appoint a Network Rail approved surveyor to
prepare a detailed method statement for the survey work to be approved by
Network Rail.
PT241.15 Monitoring of settlement of the LUL running rails and other infrastructure is
expected to be carried out by LUL’s in-house surveyors. If the Contractor is
subsequently required to carry out this work he shall employ a surveyor approved
by LUL under LUL entry procedures. The arrangement of the installation of the
targets on the tracks and ancillary structures shall be agreed with LUL as will the
frequency of monitoring and reporting. The agreed monitoring works will not form
part of the Price and cost relating to this will be dealt with as a Compensation
Event.
Thames Water Utilities Limited August 2008
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