METHODOLOGY FOR CONSTRUCTION OF PIPE CULVERTS

 CONSTRUCTION OF PIPE CULVERTS

1. Scope:

This work will consist of furnishing and installing reinforced cement concrete pipes, of the type, diameter and length required at the locations shown on the drawings in accordance with the requirements of MORTH (Ministry of Road, Transport & Highway) and Drawing.

2. Materials:

All materials used in the construction of pipe culverts will be as per MORTH in Section 1000. Each consignment of cement concrete pipes will be tested, inspected as per instruction of the competent authority.

3. Excavation for pipe:

(1) The foundation on bed for the pipe culverts will be excavated true to the lines and grades shown on the drawings or as per instruction of the competent authority. The pipes will be placed in shallow excavation of the natural ground or in open trenches cut in existing embankments, taken down to levels as shown on the drawings. In case of high embankments where the height of fill is more than three times the external diameter of the pipe, the embankment will first be built to an elevation above the top of the pipe equal to the external diameter of the pipe, and to width on each side of the pipe is minimum five times the diameter of pipe, after which a trench will be excavated and the pipe will be laid.

(2) Where trenching is involved, its width on either side of the pipe will be a minimum of 150mm or one fourth of the diameter of the pipe whichever is more and will not be more than one –third the diameter of the pipe. The sides of the trench will be as nearly vertical as possible.

(3) The pipes will be placed after the ground for the foundation becomes reasonably firm. If during excavation the material encountered is soft, spongy or other unsuitable soil, such unsuitable material will be removed to such depth, width and length as per instruction/approval of the competent authority.The excavation will then be backfilled with approved granular material, which will be properly shaped and thoroughly compacted up to the specified level.

(4) Where bed-rock or boulder strata are encountered excavation will be taken down to at least 200mm below the bottom level of the pipe with prior permission of the competent authority furthermore, the all rocks in this area be removed and the space filled with approved material, shaped to the requirements and thoroughly compacted as per specification to provide adequate support for the pipe.Trenches will be kept in dry condition until pipes are installed and the joints have hardened.

4) Bedding for Pipe Culvert:

(1) First Class bedding: The bedding surface will provide a firm foundation of uniform density throughout the length of the culvert will confirm to the specified levels and grade. The pipe will be evenly bedded on a continuous layer of well compacted approved granular material, shaped concentrically to fit the lower part of the pipe exterior for at least 10 % of its overall height or as otherwise mentioned in the drawings. The bedding material will be well graded sand or another granular material passing 5.6mm IS sieve suitably compacted/ rammed. The compacted thickness of the bedding layer will be as per the approved drawings.

(2) Concrete cradle bedding: The pipe shall be bedded in a cradle constructed of having a mix not less than M15 conforming to MORTH section 1700. The dimension of the cradle shall be as per the drawings. The pipe shall be laid properly on the concrete bedding, before the concrete has set.

5) Laying of Pipe:

The pipe shall be laid in position until the foundation has been approved by the engineer. Where two or more pipes are to be laid adjacent to each other, they shall be separated by a Distance equal to at least half of the diameter of the pipe subjected to a minimum of 450mm

6) Jointing:

The pipe shall be joined by the flush joint may be internal flush joint or external flush joint. In Either case, the end of the pipe shall be specially shaped to from a self centering joint with a Jointing space 13mm wide. The jointing space shall be filed with cement mortar 1:2 ratio mixed sufficiently dry to remain in position when forced with a trowel. Carefully fill all voids and excess Mortar material shall be removed.

7) Backfilling:

Trenches shall be backfilled immediately after the pipes have been laid and the jointing material has hardened. The backfill soil shall be clean, free from boulders, shall be approved by the Engineer. Pipe Culvert Backfilling up to 300 mm above the top of the pipe shall be carefully done and the soil thoroughly tamped or vibrated in layers thickness not exceeding 150mm. Approved light mechanical tamping equipment can be used.

8) Headwalls and other ancillary works:

Headwalls, wing walls and different works will be built as per the drawing or as Directed by the Engineer. Masonry for the wall shall conform to section 1300, 1400, 1700 as Applicable. Aprons shall conform to section 2500.

9) Opening to Traffic:

No traffic shall be permitted to cross the pipe line unless height of filling above the top of the pipeline [Cushion] is at least 600mm.