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南非土木工程施工标准 LG :管道顶进 英文原文节选 20100079 1-32 |
Prevention of subsidence during jacking
a) To ensure that overbreak is kept to a minimum, the Contractor shall ensure that the first concrete
PiDe used is so rebated that there is no substantial difference between the outside diameters of the * _
shield and the pipeline.
b) The Contractor shall ensure that excavations within the pipe are under continuous expert supervision
such that conditions at the front of the shield are always safe.
c) The Contractor shall take every reasonable precaution to ensure that no slips or runs develop at the
face such as will endanger personnel or cause cavities beyond the circumference of the lead pipe.
d) If necessary, the Contractor shall make provision for suitable de-watering of the material in the
vicinity of the leading edge of the pipe.
e ) Should any cavity occur around the outside of a pipe during the jacking process, such cavity shall be
filled immediately by the injection of suitable approved process grout through holes drilled in the pipe
walls.
f) Any subsidence occurring above the jacked pipe and arising from any cause related to jacking
operations shall be made good to the.satisfaction of the Engineer and at the Contractor's expense.
Standard procedure.
the face and boarded up where necessary.
Drainage.
Jetting.
JACKING PROCEDURE
Procedure.
bear(s) against a suitable thrust plate so that the thrust of the jack(s) is distributed adequately over
the end face of the pipe.
The rear end oE each jack shall bear against a suitably designed structure such that the force is
transferred to the surrounding material and evenly distributed over an area sufficient to ensure that the
bearing capacity of the soil is not exceeded and that no structure in the vicinity of the thrust pit is
disturbed.
At the conclusion of each day's work the pipeline being jacked shall be jacked up to
The Contractor shall ensure that the head of each excavation is drained at all times.
Under no circumstances will jetting be permitted.
Each pipe shall be advanced by means of one or more hydraulic jacks of adequate capacity that
Lubrication of Structure During Jacking. The Contractor may, with the written permission of the
Engineer, inject a suitable lubricant through preformed holes in the structure or at the cutting edge of
the shield.
Thrust and Reception Pits.
where manholes or junctions are required, as indicated on the drawings.
sufficient size to allow jacking operations to be conducted with maximum efficiency.
BACKFILLING AND DISPOSAL OF EXCAVATED MATERIAL.
and shield dismantled, the thrust and reception pits shall be backfilled to the extent necessary and in
the manner indicated on the drawings or laid down in the project specification.
Surplus excavated materials shall be disposed of as specified in the project specification.
GROUTING ANU PLUGGING. When the jacked pipeline is in its final position a stabilized sand/cement grout.
shall be injected to fill all voids between the jacked pipeline and the surrounding material. The grout
shall have a strength equal to or better than a grout consisting of one part cement and four parts sand
and shall have a slump of 120 nun.
All holes in the pipeline shall be sealed with an approved epoxy sealant.
AS-BUILT DRAWINGS.
shown on the tender drawings has been modified to suit the jacking method, the Contractor shall, on
completion of the work and before the final payment is made, supply to the Engineer transparencies
showing details of the completed structure.
to be an accurate reflection of the details of the work as constructed.
TOLERANCES
GENERAL. Subject to any requirements of the project specification imposed because of the gradientfs) of
the pipeline or the purpose for which it is required, the pipes shall be jacked into position within the
tolerances yiven in 6.2.
Should the difference between the actual and the specified position or alignment of the finished pipeline
exceed the value of the said tolerance to an extent that additional costs are incurred in locating,
installing, supporting, or maintaining any service that has been designed to be laid through the finished
pipeline, the Contractor shall bear such additional costs provided that the details of the work to be
done to relocate, install, or support the said service, and the order for the work to be done (by the
Contractor or by others) have been given by the Engineer within 30 working days after the completion of
the jacking operation.
PERMISSIBLE DEVIATIONS.
horizontally and 50 mm vertically of the designed position.
be gradual and the pipe manufacturer's stated maximum permissible draw or angular deflection shall not be
exceeded at any point. Misalignment between pipe units shall not exceed 10 mm.
CHECKING ALIGNMENT. The Contractor shall check line and level at least once during the installation of
each pipe length, and he shall take such corrective action as is necessary. A copy of the results of all
checks and a statement of any corrective measures taken shall be available for inspection on the Site,
and a copy shall be given to the Engineer as soon as the jacking has been completed.
TESTING
Except as required for the purposes of testing the pipes to be jacked (see 3.1) and to assess compliance
with the relevant requirements of SABS 677, and except for any hydraulic tests specified elsewhere in the
contract, no tests are required on the completed pipeline.
Thrust arid reception pits will in general be permitted only at positions
Thrust pits shall be of
When jacking has been completed and the jacking frame
If an alternative design by the Contractor has been accepted or if the structure
Each such transparency shall be certified by the Contractor
The position of any point of the finished pipeline shall be within 100 mm
Adjustment to line or level, or both, shall原件下载： 
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