Hanson Building Products

precast concretebox culverts

Box culvertsEasy to install, suitable for very shallowor deep fill, ideal for use in a widevariety of civil engineering applications

Hanson Building Products is thelargest producer of box culverts inthe UK, and are members of theBox Culvert Association.

Since its introduction over 40 years ago the range of box culverts we offer has continued to expand. Whilst offering increased flexibility Hanson BoxCulverts retain all their originaladvantages.

They are easy to install and can be made to suit very shallow ordeep fill. They also offer economy by being uniquely designed forparticular loading conditions and areefficiently produced in standard sizes.

As these advantages have becomewidely recognised their range ofapplications has increased makingthem ideal in a wide variety of civilengineering applications to include:

CULVERT

ASSOCIATION

BO

X

Culverting Watercourses

Attenuation Tanks

Road Crossings

Multi-cell Construction

Pipe Replacement

Pedestrian and Vehicle Subways

Sea Outfalls

Escape Tunnels

Shafts

Service Tunnels

Pumping Stations

Channels

Portals

Basements Solutions

CSO Chambers

Advantages of using box culverts

Hanson Box Culverts are availablein a range of 144 standard sizesfrom 1000mm x 600mm to6000mm to 3600mm. Non-standardsizes and internal profiles can alsobe readily provided includingshaped inverts and dwf channels.

Reference to our table of standardsizes will give the size necessary to meet any conditions which maybe required in terms of storagevolume, flow capacity etc.

For larger culvert widths, twin ormultiple sections may also beconsidered. Unlike pipes andcorrugated steel assemblies, box culverts can be designed tocarry vertical load without therelieving effect of side pressure.

Therefore, when culverts are used in multiple sections, they can be laid side by side with only a nominal gap between them.

By comparison with arched orcircular sections no flow area is lostthrough either excessive spacingapart or curved profiles.

All products are manufacturedunder a Quality ManagementSystem complying with ISO 9001:2000 and we are registered withinthe BM Trada Certification Schemefor approved quality systems.

Flexibility of range to accommodate almost any size requirement

Availability of multi-cell sections

Can be laid in multiple sections

Ease of installation

Accommodation of high storage volumes

Use with shaped invert for dry weather flow situations eg. sloping v and half round

Qualified technical department with CAD facilities, available to assist at all stages with design specification and contract development

Box culvert design specific to client requirement

Box culverts

Height Width mm mm

1000 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500 4800 5100 5400 5700 6000

600 0.53 0.65 0.83 1.01 1.19 ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘

0.50 0.64 0.86 1.07 1.29

800 0.73 0.89 1.13 1.37 1.61 1.85 2.09 2.33 ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘

0.77 0.99 1.33 1.67 2.01 2.36 2.71 3.06

1000 0.93 1.13 1.43 1.73 2.03 2.33 2.63 2.93 3.23 3.53 3.83 4.13 4.43 4.73 ✘ ✘ ✘ ✘

1.07 1.37 1.84 2.32 2.80 3.29 3.79 4.29 4.79 5.29 5.80 6.30 6.81 7.32

1200 ✘ 1.37 1.73 2.09 2.45 2.81 3.17 3.53 3.89 4.25 4.61 4.97 5.33 5.69 6.02 6.38 6.74 7.091.76 2.37 3.00 3.64 4.29 4.95 5.61 6.28 6.95 7.62 8.29 8.97 9.64 10.28 10.96 11.64 12.32

1500 ✘ ✘ 2.18 2.63 3.08 3.53 3.98 4.43 4.88 5.33 5.78 6.23 6.68 7.13 7.55 8.00 8.45 8.903.21 4.08 4.98 5.89 6.81 7.74 8.68 9.62 10.57 11.52 12.48 13.44 14.37 15.33 16.30 17.27

1800 ✘ ✘ ✘ 3.17 3.71 4.25 4.79 5.33 5.87 6.41 6.95 7.49 8.03 8.57 9.08 9.62 10.16 10.705.21 6.38 7.57 8.78 10.00 11.24 12.48 13.74 15.00 16.26 17.54 18.79 20.07 21.35 22.64

2100 ✘ ✘ ✘ ✘ 4.34 4.97 5.60 6.23 6.86 7.49 8.12 8.75 9.38 10.01 10.61 11.24 11.87 12.507.83 9.31 10.82 12.36 13.92 15.49 17.07 18.67 20.27 21.88 23.48 25.11 26.74 28.37

2400 ✘ ✘ ✘ ✘ ✘ 5.69 6.41 7.13 7.85 8.57 9.29 10.01 10.73 11.45 12.14 12.86 13.58 14.3011.11 12.94 14.81 16.70 18.61 20.55 22.50 24.46 26.43 28.40 30.40 32.40 34.41

2700 ✘ ✘ ✘ ✘ ✘ ✘ 7.22 8.03 8.84 9.65 10.46 11.27 12.08 12.89 13.67 14.48 15.29 16.1015.11 17.32 19.56 21.84 24.14 26.46 28.80 31.15 33.52 35.90 38.29 40.70

3000 ✘ ✘ ✘ ✘ ✘ ✘ ✘ 8.93 9.83 10.73 11.63 12.53 13.43 14.33 15.20 16.10 17.00 17.9019.88 22.49 25.14 27.82 30.53 33.27 36.02 38.80 41.59 44.40 47.22

3300 ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ 10.82 11.81 12.80 13.79 14.78 15.77 16.73 17.72 18.71 19.7025.48 28.52 31.59 34.71 37.85 41.02 44.22 47.44 50.68 53.93

3600 ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ 12.89 13.97 15.05 16.13 17.21 18.26 19.34 20.42 21.5031.95 35.43 38.96 42.53 46.13 49.77 53.43 57.11 60.81

Flow area m2 Discharge rate m3/s

1. The standard range of box culverts generally have flat inverts and 190mm corner splays up to 4800mm span and 225mm splays from 5100mm to 6000mmspan and a maximum length of 2m.

2. Sizes other than those stated can be manufactured to suit customer requirements.

3. Special internal profiles, shaped inverts and dry weather flow channels can be produced and are available on request.

4. Tapered units for bends, units with manhole openings and pipe access holes can be produced and are available on request.

5. All box culverts are manufactured to orderand to the specific required design criteria,the external loading conditions will govern the wall, roof and floor thickness, unit length and reinforcement content.

6. Joints are a standard rebate within the wall of the unit and the box culverts can be jointed using sealant strip to provide a seal and flexible joint if required.

7. Special insert pins are cast in to each box culvert to enable them to be lifted.

8. Channel units can also be produced if required.

Table No.1 Dimensions, flow area and discharge rate

Table No.2Circular pipe discharge rates forcomparison with standard culvertsDiameter Flow area Discharge

DN m2 rate m3/s900 0.64 0.67

1050 0.87 1.001200 1.13 1.421350 1.43 1.931500 1.77 2.541650 2.14 3.251800 2.54 4.082100 3.46 6.112400 4.52 8.65

Table No.3Gradient multiplier

Gradient Multiplier1 in 1000 1.01 in 800 1.11 in 700 1.21 in 600 1.31 in 500 1.41 in 400 1.61 in 300 1.81 in 250 2.0

Table No.4Roughness multiplier

Roughnesscoefficient ks Multiplier

0.06 1.110.15 1.050.30 1.000.60 0.931.50 0.85

Notes

Technical enquiriesTel: (01773) 602432

Box culvertsStandard specifications andguidance on installation

Hydraulic design

Discharge rates for box culverts inthe Hanson standard range arecalculated for a gradient of 1 in1000 in accordance with theColebrook-White equationassuming the culvert running fullunder uniform flow conditions.Comparable discharge rates forcircular pipes are given in the Table2 (overleaf).

For any gradient between1 in 1000and 1 in 250, the gradientmultiplier (Table 3 overleaf) shouldbe applied. A value of 0.3mm hasbeen assumed for roughnesscoefficient, ks, which dependsupon the accuracy of laying andjointing in addition to the quality ofthe culvert surface. Where adifferent value is required, thedischarge rate at the appropriategradient should be adjusted by theuse of the roughness multiplier(Table 4 overleaf).

Thus, for a 2400 x 1200 sectionlaid at a gradient of 1 in 500 and

with an assumed roughnesscoefficient of 0.6mm, the dischargerate is given by 4.29 x 1.4 x 0.93 = 5.59m3/s. The flow capacity of aculvert is determined by a numberof different factors. In addition tothe gradient and roughnesscoefficient, the geometry of theinlet and outlet and the tailwaterlevel can affect the mode of flowand may prevent the culvert fromrunning full or under uniform flowconditions. In such cases the flowcapacity will be lower than the fulldischarge rate.

Surface loading and fill depth

Loading applied at the groundsurface and weight of fill materialproduce a combination of verticaland horizontal forces on the boxculvert. Surface loading may bespecified as a standard loadingtype, equivalent uniform loading orindividual wheel loads. The criticalload on a culvert can occur atminimum or maximum fill.

Each enquiry for a culvert shouldstate the minimum and maximumfill depth and the amount or type ofsurface loading. It is recommendedthat the minimum fill depth shouldbe not less than 200mm or onefifteenth of the internal width ofthe culvert if this is greater.

Design and detailing

Box culverts are generally designedand detailed in accordance withthe Box Culvert AssociationStandard Specification whichcovers materials, manufacturingtolerances, external loading designand detailing standards.

Box culverts carrying highwayloading or railway loading aredesigned to current standards and specification as stipulated bythe client.

The lowest grade of concrete used is C50 with a 20mmmaximum size of aggregate. The nominal cover toreinforcement is 30mm.

An experienced team of engineersand technicians backed by CADfacilities provide a flexible andcomprehensive design anddetailing service enabling theclients design and specificationcriteria to be satisfied.

Delivery and offloading

It is the contractors responsibilityto offload the box culverts ondelivery. A hard level access areashould be provided which can beused safely by standard articulateddelivery vehicles. The contractorshould provide a suitable crane ofadequate capacity for lifting theculvert. For reasons of safety andeconomy certain box culverts aredelivered to site on end rather thanas laid, and will require a safemethod of turning duringoffloading. A data sheet givingguidance of lifting and turning isavailable and is issued to clientsprior to the first delivery.

The offloaded box culverts shouldbe levelled carefully on a firm levelbase away from the edge of thetrench, and if any furthermovement is required it should beby lifting; the culvert should neverbe dragged or dropped.

Bedding, laying andbackfilling

Excavation can be kept to aminimum with only nominalworking space required on eachside of the box culvert. Whenworking in trenches the normalrequirements for health and safetymust always be observed.

The base of the trench should beuniformly prepared before laying a200mm bedding of compactedgranular material over the full width of the trench. A surfaceblinding of the fine material willassist levelling. Local packings aresubject to settlement and shouldnot be used. As an alternative togranular bedding a concreteblinding layer is sometimespreferred to protect the formationor to allow a faster rate of layingthe culverts.

A layer of unreinforced concreteapproximately 75mm thick on atrench bottom which has been wellprepared to provide a uniformsupport is generally sufficient.

A culvert line is usually laid directly on the bedding startingfrom the downstream end with the sockets facing upstream, to receive the next culvert.

The trench should be backfilled assoon as possible after the culverthas been laid and it should befilled evenly on each side of thetrench. Backfilling should continuein 200mm compacted layers toreach the required depth of cover.

Where loads from constructionplant may exceed the designload of the box culvertprotective measures will berequired. This is particularlyrelevant at shallow fill depths.

Jointing

The culvert sections generally haverebated joints and can be laidopen, or sealed using pre formedstrips and/or pointing materials.Reference should be made to thejointing material manufacturer’sspecification and recommendationfor use of the product.

A system using preformed strip withinthe joint is most commonly used.When the strip is bitumen basedthe joint faces should be cleaned,primed and allowed to dry. Thestrip is then applied to the internalcorner of the socket just beforethe culvert is laid in the trench.

Joints are closed to a nominal gapby pulling against previously laid culverts with an applied load of

approximately one tonne per metreof strip plus about half of theweight of the culvert unit toovercome base friction, less if theunit is suspended from the cranewhilst jointing. Heat may berequired to soften the strip whenworking at low temperature.

When the box culvert is ofsufficient size for access, it can bepointed internally with anelastomeric or bitumen basedmaterial using a suitable primer.Not all methods of jointing,however, should be expected to be completely watertight.

For further information,technical & sales enquiriesplease contact:

Hanson Building ProductsBirchwood Way, Cotes Park Industrial Estate,Alfreton, Derbyshire, DE55 4NHTel: (01773) 602432 Fax:(01773) 603134

25

Compressed strip if used

Internal pointing if used

75

Internal Face

Jointing diagram

Floors and Precast Division

0870 6097094Hanson Building Products

Head Office

Stewartby

Bedford

MK43 9L2

Tel: 08705 258258

Website: www.hanson.biz