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南非土木工程施工标准 LE:雨水排放设施 英文原文节选 20100079 1-30 |
Prefabricated Chambers and Shafts. Prefabricated manhole sections may be of spun concrete, asbestos
cement, glass-reinforced polyester, PVC, or such other materials a s a r e required i n terms of the
schedule. P ~ e c a s t concrete cylinders shall comply with the applicable requirements of SABS 1294.
Scctional spun concrete cylinders shall comply with the requirements for pipes of SC type and Class A of
S A W 677. Jointing between cylinders shall be of the interlocking self-centring type.
Manhole Covers, Grid I n l e t s , etc. Covers and frames for manholes and grid i n l e t s shall be supplied in
matching sets.
paint) to enable the s e t s t o be identified. The Contractor shall ensure t h a t , when installed, the covers
and frames still comply with the requirements of SABS 558 for freedom from warp and evenness of seating.
Unless otherwise required in terms of the project specification, covers and frames for manholes shall
comply with the requirements of SABS 558 for Type 2B in the case of manholes in roads and other areas
subject to road t r a f f i c loads, and Type 4 in the case of manholes in areas not subject to road t r a f f i c
loads.
Step Irons. Step irons shall comply with the applicable requirements of BS 1247 and shall be of suitable
length for the wall of the manhole into which they are to be built.
GEOFABRIC BLANKET.
polypropylene, polyethylene, a polyester, a polyamide, or a co-polymer of vinyl chloride and
vinylidene-chloride, or any combination of these polymers, and shall contain such additives as are
necessary t o render the filaments r e s i s t a n t to t h e e f f e c t s of ultra-violet radiation and heat.
The amount of water absorbed by the fabric a f t e r 24 h soaking in watcr a t 20 OC shall be less than 1 % by
mass, and its equivalent open size (EOS), strength, and other characteristics shall be as specified in
the project specification.
The Engineer's approval of the make and grade of the geofabric shall be obiained by the Contractor before
the Contractor orders any geofabric or uses it on the Works.
PLANT
HANDLING AND RIGGING. The plant and rigging equipment used by the Contractor for handling and placing
any pref'abricated culvert unit shall be such that the shell of the unit is not over-stressed a t any t i m e
during construction.
CONSTRUCTION
TRENCH BOTTOM
Pipe Culverts.
the applicable requirements of SABS 1200 DB and bedding shall comply with the applicable requirements of
SABS 1200 LB. Trenches shall be kept sufficiently dry t o allow proper and safe laying, jointing, and
bedding of the pipeline.
The cover and frame of each set shall bear a s e r i a l number (applied by means of o i l
The synthetic f i b r e s of a geofabric blanket shall consist of at l e a s t 85 % by mass of
The preparation of the trench bottom for pipes a t the depth specified shall comply with
Portal and Rectangular Culverts
Exceot in hard rock (see 5.1.2.3). the trench shall be excavated to a depth of 75 mm. or such other deDth
as may be shown on the drawings, below the level of the underside of the precast i n v e r t s l a b or to the
level of the underside of the cast-in-situ invert slab, as applicable. Where the culvert is to be
constructed i n new f i l l , the height of the bank constructed shall be such t h a t the depth of material over
the top of the culvert a f t e r it has been laid w i l l be a t l e a s t 100 mm or such greater depth as may be
shown on the drawings.
The excavation shall be trimmed to the shape of the invert of the culvert unit and, except on a rock
foundation, a bed of selected granular material as specified in Subclause 3.1 of SABS 1200 LB, of
thickness a t l e a s t 75 mm, shall be placed, compacted, and shaped to enable the culvert units to be bedded
as shown on the drawings, or as required in terms of the project specification.
where hard rock is encountered the depth of excavation shall be a t l e a s t 200 mm below, and t o the shape
of, the underside of the culvert f l o o r u n i t , and t h i s space shall be f i l l e d with granular material as
specified in 5.1.2.2.
Unsuitable Founding Conditions. Where, because s o f t , soggy, spongy, or otherwise unsuitable material is
encountered, the bottom of the trench as excavated does not provide a suitable firm foundation for the
culvert, the unsuitable material shall be excavated to a depth below the bottom of the culvert indicated
by the Engineer and replaced with gravel or other approved granular material compacted to a t l e a s t 90 %
of modified AASHTO maximum density. When so oqdered, the Contractor shall construct a layer of concrete
blinding to provide a suitable working floor.
Width of Excavation
a) Portal and rectangular culverts. The width of excavation shall be equal to the t o t a l outside width of
the culvert portal plus a minimum of 1,O m for both single and multiple openings. In the case of
rectangular culverts having a span of up to 1 200 mm and located near the finished surface, the Engineer
may require that the excavation width shall be the net width of cast-in-situ i n v e r t s l a b s or the net
width of precast invert slabs plus 100 mm. The additional width w i l l apply where backfilling of the
trench with concrete is required in terms of the project specification.
b) Pipe culverts. The requirements for minimum base width given in Subclause 5.2 of SABS 1200 DB shall
apply.
BEDDING AND LAYING
General. Unless otherwise shown on the drawings or directed, construction of culverts s h a l l , as far as
is practicable, begin a t the lower end. The Engineer may order that the end of the l a s t unit of short
culverts, or of that nearest the upper catchpit or manhole in the case of long drains, be cut to the
length or skew required, or both.
Precast u n i t s s h a l l be l i f t e d and handled only by means of l i f t i n g devices approved by the manufacturer.
Lifting eyes shall be caulked with a suitable mortar a f t e r the units have been installed.
The Contractor shall exercise due care not to damage, overstress, or displace any culverts by the
imposition of any loads such as may be caused by the movement of his own vehicles or compaction
equipment. Where superimposed moving loads in excess of those prescribed in the applicable road t r a f f i c
ordinance are, during the construction of the Works, likely to pass over completed culverts, the
Contractor shall provide sufficient additional cover over the culverts to ensure that the design s t r e s s e s
on the culverts are not exceeded.原件下载：  |
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