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南非土木工程施工标准 DP1部分：埋置管道与预制涵洞的土方工程 英文原文节选 20100079 2-10 |
4.2.6.2 Areas subjected to traffic loads
In areas subjected to road traffic loads and in such other areas as specified in the specification data
(see annex A), trenches shall be backfilled in layers of thickness (after compaction) that do not
exceed 150 mm and the material shall be compacted to 93 % of modified AASHTO maximum dry
density in the case of cohesive soil, or 98 % in the case of non-cohesive soil.
NOTE It is extremely difficult to compact a layer in excess of 100 mm to the required density with walk-behind
rollers. Where a 150 mm layer is required, it should be compacted in two 75 mm layers
4.2.7 Cement stabilized backfill
4.2.7.1 Where cement stabilization is required, loose backfill and common cement shall be mixed
by hand or by means of a suitable mixer in the proportions stated in 4.1.7 to produce a homogenous
mixture of soil and cement before being placed in the trench. Sufficient water shall be added,
without saturating the mixture, to achieve uniform mixing and compaction.
4.2.7.2 The processing, placing and compaction shall be completed within 6 h from the time that
the common cement is first added to the material.
4.2.7.3 Cement stabilized backfill shall be compacted to 93 % of modified AASHTO maximum dry
density.
4.2.8 Reinstatement of surfaces
4.2.8.1 Width to be reinstated
4.2.8.1.1 In all cases, the reinstatement of surfaces over the full extent of the top of the actual
excavation shall comply with the applicable requirements given in 4.2.8.2 to 4.2.8.5 (inclusive).
4.2.8.1.2 Except as allowed in terms of 4.2.8.1.3, where a pipe trench crosses a surfaced road or
paved area or runs along the edge of such a road or area, the total actual excavation, regardless of
the base width as determined in terms of 4.2.2.3, that encroaches on such road or area shall be
backfilled and reinstated as specified in the applicable requirements of 4.2.8.2 to 4.2.8.5 (inclusive).
4.2.8.1.3 In the case of gravel roads or bitumen-surfaced roads, the reinstatement specified in
4.2.8.3, 4.2.8.4 and 4.2.8.5 shall be confined to that portion of the road reserve that had or will have
a gravel or bitumen surface.
4.2.8.2 Private property and commonage
The top 300 mm layer of each trench that will not be subjected to road traffic loads shall be of such
topsoil as is available in addition to soft material from excavations. The finished surface of
backfilling that is left proud of the surrounding ground to allow for initial settlement shall be not more
than 150 mm above the surrounding ground level. Any settlement below original ground level that
occurs shall, as soon as is practicable, be made good with material of the same quality as that
adjacent to the trench, except as otherwise required in terms of the specification data.
4.2.8.3 Gravel roads
Immediately after completion of the backfilling to the top of the subgrade level of a trench that
crosses or runs along a gravel road, the road surface shall be reinstated by filling the remainder of
the trench with a suitable well-graded and well-compacted hard-wearing gravel surface of thickness
at least 150 mm and of quality equal to that of the existing road surface. The gravel layer may be
finished with a slight camber in order to allow for initial settlement but, particularly where the new
gravel surface is transverse to the flow of traffic, it shall not be left so far proud of the adjacent road
surface as to cause excessive jolting of any vehicle proceeding at normal speed.
SANS 2001-DP1:2008
Edition 1
19
4.2.8.4 Bitumen roads – Sub-base and base
4.2.8.4.1 In the case of a bitumen-surfaced road, as soon as is practicable after completion of
backfilling to subgrade level, the sub-base and base shall be reinstated using material of quality at
least equal to that of the material used in the construction of the road. The depth of each course in
the reinstated portion shall be at least equal to the thickness of the existing sub-base or base, as
applicable, or at least 100 mm, whichever is greater, and each course shall be compacted to a
density at least equal to that of the adjacent existing materials, except that where there is no
existing sub-base, the thickness of base that is placed directly on the subgrade shall be at least
150 mm. The base shall be finished slightly above the road surface to allow for initial settlement, but
shall not be left so far proud of the adjacent road surface as to cause excessive jolting of any
vehicle proceeding at normal speed. The gravel surface shall be maintained at a standard suitable
for normal traffic until the bitumen surfacing has been reinstated.
4.2.8.4.2 If a surface of a road with a stabilized base has been disturbed, the base shall be
replaced with a crusher-run base that complies with the requirements of SANS 1200 MF.
4.2.8.4.3 Except where immediate reinstatement of the bitumen surface is required in terms of the
specification data (see annex A), the bitumen surface shall be reinstated after sufficient time has
elapsed to show up compacted areas that have not been compacted to specification and after such
areas have been made good.
4.2.8.5 Bitumen roads – Surfacing
4.2.8.5.1 General
The surface of a bitumen road shall be reinstated with asphalt of the thickness specified in the
scope of work.
4.2.8.5.2 Base material
The base material shall be graded to a level sufficiently below the final road surface to allow the
bitumen surfacing to be accommodated, and the edges of the existing bitumen wearing course shall
be cut back vertically to a straight line. Before the bituminous construction is commenced, all loose
materials and dust shall have been removed with brooms.
4.2.8.5.3 Asphalt surface
4.2.8.5.3.1 Unless otherwise specified in the specification data, a prime coat consisting of a
suitable primer shall be sprayed at an appropriate rate and temperature. The cut edges of the
existing wearing course shall also be prepared with a suitable primer. A suitable tack coat shall be
applied after the prime coat.
4.2.8.5.3.2 A compacted asphalt surface of the thickness specified in the scope of work shall then
be laid, using either of the mixes specified in 4.1.6.4. The materials shall be thoroughly mixed in a
suitable mechanically operated mixer for at least 1,5 min before being spread evenly over the
surface to obtain the specified compacted thickness and then compacted with a suitable roller to a
surface matching the existing surface in line and level.
4.2.8.6 Segmented paving
Segmented paved surfaces shall be reinstated using paving units that have the same shape,
dimensions and properties as the existing surface, in accordance with the relevant requirements of
SANS 1200 MJ.
4.2.8.7 Maintenance of reinstated surfaces
4.2.8.7.1 The reinstated surfaces of roads shall be maintained and any damage due to any
subsidence, pothole or other unevenness shall be made good immediately.
SANS 2001-DP1:2008
Edition 1
20
4.2.8.7.2 In order to locate any subsidence, regular inspections of all backfilled excavations shall
be carried out. Additional inspections shall be carried out immediately after rainfalls.
4.2.9 Damage to road surfaces
Where, during the execution of the works, any road or paved surface adjacent to a trench has been
damaged in any way whatsoever by the construction equipment, such surface shall, as soon as is
practicable, be repaired to a condition at least equivalent to that previously existing.原件下载：  |
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