NATIONAL ALUMINIUM COMPANY LIMITED - Rites

cementitious coating in two layers ( slurry mix application ) as per manufacturer’s
specification. 50 mm thick ck P. C. C. ( 1 2 : 4 ) with 10 mm nominal size stone aggregates shall
then be laid over the polymer modified cementitious coating before laying the raft.
Hopper shall have removable type steel grating cover. The opening size for the grating shall
be 300 mm x 300 mm. Machinery hatches shall have removable steel chequered plate cover.
Hopper grating shall be built of min. 200mm x 36mm thick flats. No painting/galvanization
shall be provided in gratings. However, two coats of red oxide primer to be provided
immediately after fabrication.
Catwalk shall be provided along the hopper. Each machinery hatch shall be provided with a
pair of R. C. C. stair for providing access to the base of track hopper / machinery hatch. Both
the stairs shall be interconnected at ssuitable
height.
Plinth protection along with drains shall be provided along the Hopper and around
machinery hatches. However, paving shall also be provided around machinery hatches.
The wagon tippler hopper is a deep underground structure which is subjecte subjected to direct load
from the loaded wagons / loco due to the rake movement over it, in addition to load due to
coal filled hopper and lateral earth pressure. The railway loads, analysis and design of
hopper, machinery hatches, transfer point and the portion oof
f tunnel subjected to rail loads
shall be as specified in design criteria. Coefficient of dynamic augmentation shall be worked
out for a train speed of 30 kms per hour.
Earth pressure to be considered for design shall be due to earth pressure at rest (K
0)condition condition only. Earth pressure due to surcharge intensity of Railway Loads (where
applicable) or Uniformly Distributed Load (U. D. L) of intensity 2 T / Sq. M. whichever is
critical, shall be considered in the design.
A minimum safety factor of 1.2 against uplift of hopper, machinery hatches, wagon tippler,
transfer points (underground or with basement) and tunnels, due to ground water shall be
ensured during execution and after execution, considering dead weight of the structure to
be 0.9 times only, groun ground d water table at adjoining formation level and soil wedge angle of
not more than 15 degrees.
Also, FOS against uplift, to be taken as 1.0, considering the dead wt. of structure and soil
resting on side projections if any in the vertical plane. Inclined wed wedge ge action of soil shall not
be considered in this case.
Walkway width and hand railing shall be provided as specified in the tender drawing.
Wherever, slope of tunnel exceeds 10 o, R. C. C. steps shall be provided for the entire width
of each walkway.
Wagon n Tippler hopper structure shall be analyzed and designed for the worst load
combinations.
4.2 Overhead / Ground Conveyor Galleries and Trestles
Overhead conveyors shall be located in a suitably enclosed gallery of structural steel. The
overhead gallery shall consist of two vertical latticed girders having rigid jointed portal frame
at both ends. Cross beams at floor level supporting conveyor stringer beams shall be made
of single rolled steel beam or single channel section (ISMB or ISMC) or plate girder.
Horizontal bracings are to be provided at top & bottom plan of the gallery (latticed girders
shall be braced together in plan at the top and bottom).Common end portal frame shall not
be used for adjacent conveyor spans. Roof trussshall be provided at upp upper node points of
latticed girders to form an enclosure. Themaximum span of overhead gallery shall be limited
to 25 meters unless higher spanis required due to site conditions, which shall be subject to
approval of the Engineer.The gallery should as far as possible be erected as a box section
keeping all thevertical and horizontal bracing tied in proper position. The gallery should be
checkedfor all erection stresses that are likely to develop during handling and erection and
ifrequired, temporary strengthe strengthening ning of gallery members during erection shall be made.Seal
Technical Specification:Sec-7, Civil
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