2. The different types of culverts: – In this section, various culvert types are described, along with models created in Midas Civil.
They are the most common type of culverts since they are economical and are easier to install. Depending on the site conditions and constraints, different shapes of pipe culverts can be seen, such as circular, elliptical and pipe arch. Advantages:
Any desired strength is achievable by proper mix-design, thickness, and reinforcement. They are economical and easy to install. A pipe culvert can resist high tensile and compressive stresses.
Pipe culverts are susceptible to crown erosion due to organic and chemical reactions.
Figure 1: Pipe Culvert Figure 2: Pipe Culvert-3D Midas Civil model and the boundary conditions assigned
Steel, stone masonry, concrete, RCC, etc., are used to construct arch culverts. Unlike box culverts, they are erected without disrupting the water flow; construction is quick. Arch type of culvert maintains the wash bed’s natural integrity and is called a low-profile culvert. Advantages:
Greater spans can be achieved by arch action. Greater hydraulic efficiency. It can be constructed without disrupting the water flow.
Need stable support. The soil bearing capacity should be high enough to withstand the support reactions. Need timely maintenance.
Figure 3 : Arch Culvert Figure 4 : Arch Culvert- 3D Midas Civil model and the displacement contour due to vertical earth pressure
Pipe-Arch culverts are suitable for large waterway openings with a more significant hydraulic advantage. Moreover, they provide low clearance and are, much more artistic. Pipe arches are particularly useful for sites with limited headroom and a hydraulic advantage at low flows. Advantages:
Suitable for waterways with large discharge. An increased headroom is achieved. Greater hydraulic efficiency is achieved.
Figure 5 : Pipe-Arch Culvert Figure 6 : Pipe-Arch Culvert modelled in Midas Civil
Box culvert is a monolithically cast, rigid framed structure suitable for non-perennial streams where the soil is weak. The bottom slab reduces the pressure on the ground below. Therefore, a separate foundation is not required making them economical. Even though box culverts are easy to install, a dry surface is needed for installation. Advantages:
Suitable for non-perennial streams, where the soil bearing capacity is low. The bottom slab reduces the soil pressure. They are very economical.
Figure 7 : Box Culvert Figure 8: 3D and 2D models of Box Culvert in Midas Civil
Bridge culverts act as a bridge and a culvert, thus serving a dual purpose. Generally, these culverts are rectangular and built on rivers or canals. The foundation rests below ground level, and the pavement surface is on top of the culverts. Figure 9 : Bridge Culvert Figure 10 : Bridge culvert – 3D Midas Civil model and the bending moment contour due to traffic loads 3. Loads acting on culverts
Dead loads mainly constitute the self-weight of the culverts. The weight of the wearing course, the crash barrier, and other fixed loads are also considered dead loads.
Earth pressure loads
A linear horizontal soil pressure acts along the vertical walls, and weep holes release the pore pressure. A uniform vertical surcharge is applied on the top slab in deep culverts.
Most of the culverts experience moving loads throughout their lifetime. Traffic loads should be applied over culverts like bridges following the various codes used worldwide. The upcoming articles will discuss the live load dispersion on culverts and the different design codes used.
The buoyant force is the upward thrust acting on culverts due to buoyancy. In many cases, the structure gets uplifted and carried away due to strong water currents. The weight of culverts should be able to withstand this uplift.
Stresses caused due to expansion and contraction of indeterminate structures like culverts due to temperature variation are known as temperature stresses. They can be classified into 2: uniform temperature – stresses caused due to uniform heating and cooling of the structure (climatic changes) and gradient temperature stresses – caused due to differential heating and cooling of members along the section. Apart from the above-listed loads, dynamic loads are also considered in case of rail tracks loading on top.
What is the procedure adopted for the construction of box culvert?
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.
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.
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What is the span of a box culvert?
What is the difference between a box culvert and a bridge? – When Box Culverts are installed as a single barrel with a span less than 20′, they are considered a culvert. However, when the total span, whether as a single barrel or multiple barrels, is greater than 20′, they are considered bridges by the structure’s owners.
What are the different types of culvert?
What is a Culvert? – The culvert is a small cross drainage structure spanning six meters or less between the inner face of the wall. It may be like a bridge designed to allow carrier or pedestrian traffic to cross the stream providing adequate clearance from high flood levels.
What are box culverts made of?
Cast-In-Place Concrete Box Culverts – Box culverts that are made of reinforced concrete and fabricated in the field are considered cast-in-place. These structures are built with concrete and rebar at the project site. Forms are constructed to outline and create the dimensions and shape of the box culvert, and concrete is poured into them.
Building the box culvert in the field requires engineering and planning that make this method a longer installation process than working with Precast structures. However, since these culverts are explicitly designed for the project site, project owners have more size ranges and specialty options to meet their needs.
The design of these structures often requires that the project design engineers perform structural and hydraulic analysis to ensure that the Box Culvert meets the project requirements.