BOX CULVERT CONSTRUCTION

                 construction of Box culvert.

This article provides a detailed procedure adopted for the construction of Box culvert. The Scope of the Quality Plan covers the following activity.

1.   Site Clearance including removal of trees, Bushes, stumps etc.

2.   Excavation necessary for the construction of box culvert as per                   specification

3.  Construction of Box culvert as per technical specification 

                DEFINITIONS

MoRTH : Ministry of surface Road Transport & Highways

IRC       : Indian Road Congress

IS          : Indian Standards

       CONSTRUCTION METHODOLOGY

    Equipments to be deployed:

                Mobilization of Plant / Equipment / Machinery shall be as per requirement of finalized  construction schedule / programmed.

 

Description                         Capacity                   No (s)

Batch Plant (Mobile)          15cum/hr                   1 No.

Transit Mixer                     6 Cum                       5- Nos. 

Concrete Pump                    30 cum / hr               1 nos

Trailer                                                                 1 no

Truck                                                                    2 nos

Dumper                                                                 6 nos

JCB / Loader                                                         2 nos

Vibrators                                                              8 nos

 

      Site Clearance Works:

                Site clearance, grubbing, dismantling of existing structure and disposal of unserviceable material at designated area and stacking of serviceable material shall be carried out as per MoRTH specification, 

       Survey and Setting out works:

                After the site has been cleared, the limits of excavations shall be set out after center line marking true to lines, curves, slopes, grades and sections as per shown on the drawings as directed by the engineer and as per established bench marks / co-ordinates.

                All the survey instruments used shall be calibrated periodically. Survey check reports / other relevant data shall be kept in formats.      

     Construction operations

A) Excavation: - After the site has been cleaned according to clause 201. The limits of excavation shall be setout true to lines, curves and slopes to clause 301.3.1. The excavation shall be carried out as per MoRTH clauses 304.3.2 & 2903. The depth to which excavation shall be as shown on the drawings, where water is met with in excavation due to stream flow, seepage, springs etc; adequate measure shall be taken to pump out water to keep foundation trenches dry.

B) The bottom of foundation shall be leveled both longitudinally and transversely and compacted by suitable compactor to achieve the required compaction.

C) Over compacted earth a leveling course of concrete of required thickness and grade as specified in drawing shall be laid.

D) Reinforcement shall be corrosion resistant reinforcing bars – HYSD/TMT type or equivalent with minimum yield stress of 415 Mpa confirming to IS specification 1786. The reinforcement steel will be procured from approved source. Different dia of reinforcement steel shall be stocked separately above ground level / floor level to avoid contact with water. Bar bending schedule shall be prepared and got approved from engineer. Bars shall be cut and bent cold to the specified shape and dimension. Reinforcement bars shall be placed accurately in position as shown on drawings. The bars crossing one another shall be tied together at every intersection with binding wire, that should be annealed 18-20 gauges mild steel. Necessary stays, a concrete blocks, chair spacer shall be provided to fix the reinforcement in its correct position. Placing and fixing of reinforcement shall be inspected and approved by engineer before placing of concrete.

E) Shuttering plates made of 3mm thick plates welded with angles of 50x50x6 standard size shall be used for inside and outside wall shuttering vertical props and cross bracings of sufficient strength shall be used to protect any deformation of concrete.  All the joints shall be properly sealed. PVC joint, sealing tapes, foam will be used in order to prevent leakage of slurry.

F) Weep holes shall be provided as per drawing and specification.

G) Concrete of required grade and specification and as per approved mix design shall be mixed at batching plant and transported to site by using Transit Mixers. Concrete of grade as specified in drawings will be laid in the bottom raft portion including haunch portion. Then sidewall will be constructed in one lift depending on the height mentioned in drawing. Concrete will be poured in the erected formwork by using Chutes or manually and compacted by using needle vibrators.  Second phase of shuttering and formwork shall be erected for the top slab and remaining portion of wall. Tying of slab reinforcement shall be done as per drawing. Then concrete shall be poured and compacted. Free fall of concrete exceeding 1.5 mt is not allowed. Curing shall be done for 14 days by keeping surface moist. Cubes shall be taken and tested for compressive strength. Slump shall be taken at delivery point to maintain the workability of the concrete.

H) In case of widening, for joining with existing slab culvert 600 mm slab of existing structure slab to be dismantled and over lapped with the new slab reinforcement. If joining with existing Arch culvert, 300 mm  Arch of culvert will be dismantled and reinforcement of new culvert will be embedded in that.

        TESTING AND ACCEPTANCE PROCEDURES:

The materials used in construction are tested as per relevant IS code and specifications to verify its suitability.

1.         Cement (As per IS 383 and IS 2386)

2.         Coarse aggregate (As per IS 383 and IS 2386)

3.         Fine aggregate (As per IS 383 and IS 2386)

4.         Reinforcement (IS 1786 and IS 432)

5.       Water – water used for mixing and curing shall be clean and          free from injurious amounts of oils, acids, salts, sugar etc.

6.      Cube strength – 150mm cube shall be made cured and tested at       the age of 28 days for compressive strength in accordance with     IS 516.

All the Inspection and Test requirements shall be followed as per Technical Specifications and other Codes/Standards.

     SAFETY:

• All the personnel in the operation shall be wearing the personal safety gear like safety helmets, belts and shoes during the operations.
• The work site would be cleaned of rubbish, loose materials, cut rebars from the site at regular intervals and good house keeping would be maintained at site.
• During welding the operators shall be wearing safety goggles.
• Safe access will be made for each work inspection and activity.
• The grabs, links, chains, wire ropes, slings etc will be inspected regularly and changed if required necessary.