FOR RESIDENTIAL, COMMERCIAL AND …cms.esi.info/Media/documents/Wavin_Ultraribdesign_ML.pdf6....

Below Ground DrainageSystems: UltraRib

Design Guide

CI/SfB(52.3) In6

July 2000 UR101

Uniclass EPICJR12 L21721 P7114 J344 X725

Intelligent Solutions for Below Ground Projects

FOR RESIDENTIAL,

COMMERCIAL AND

INDUSTRIAL APPLICATIONS

OSMA ULTRARIB Page

Introduction 1-2

Pipe Technology and Joint Design 3

Material, The Osma UltraRib System,Standards and Acceptance 4

Hydraulic Design -Foul and Surface Water Sewer 5-6

Structural Design 7-11

Protection of Pipes under Roads 12

Pipe Sizing Tables 13-14

Structural Design Tables 15-16

Osma UltraRib System

Contents

O S M A U L T R A R I B D E S I G N M A N U A L

Wavin is credited with inventing and pioneering

the use of plastic pipe for water distribution and

for over twenty five years, has lead the way in the

development and production of unplasticized

polyvinyl chloride (PVC-U) underground

drainage and sewerage systems.

Owned equally by the Overijsel Water Authority in Holland and CVC, the company has

grown spectacularly since its formation in 1955 and now employs over 4500 people

operating within 26 countries with a rapidly developing base in Central and Eastern

Europe.

Here in the UK, utilising the Osma brand name, Wavin Building Products has become

market leader in both above and below ground drainage. Over 500 people are employed

on a 30 acre site in Chippenham, Wiltshire, in design, manufacture and distribution.

The highly automated factory contains 35 microprocessor controlled injection

moulding machines manufacturing fittings while 8 extrusion lines produce pipe and

gutters. Wavin prides itself on the quality of these products and the services it provides.

As a result, Wavin has achieved BS EN ISO 9002 Registered Firm Status and is the first in

the plastic pipes industry to be accredited with BS 7750, the new British Standard for

environmental management.

Wherever possible, Wavin ensures that its products are manufactured to a British

Standard or, where no standard exists, the components are independently assessed by

the British Board of Agrément.

In addition to supplying the highest

quality products, Wavin also offers

unrivalled service levels including an

extensive Computer Aided Design service

for specifiers. Sixteen workstations provide

drawings showing optimum drainage

layouts together with a detailed schedule

of components. This is a service which

Wavin continues to offer free to the

construction industry.

PVC water pipeswere developed by

the OverijsselWater Board in the

early 1950s.

The OsmaUltraRib systemreceived the BSI Kitemark certification in1995.

O S M A U L T R A R I B S Y S T E M1Introduction


1. INTRODUCTION

It is a well known fact that buried pipes used for

the transportation of either water or sewage,

represents one of the largest infrastructure

investments for a utility or local authority.

Once installed, these systems also represent

a significant annual cost in terms of their

operational and maintenance activities.

Therefore, great effort has always been made to

develop technical systems which are

fit-for-purpose.

The suitability of any system may therefore

be expressed in terms of the degree to which

its functional requirements are expected to be

fulfilled during the total lifetime of the system.

These functional requirements cover aspects

such as the long term strength of the pipe

material, its resistance to degradation and

biological attack plus the integrity of the system

in terms of water tightness.

One major consideration for any engineer

designing any buried pipe system, be it rigid or

flexible, is its structural design. The structural

design of a pipe can be affected by many outside

influences such as soil and traffic loads, ground

consolidation and water levels.

In addition to the above influences, flexible

systems manufactured from materials such as

PVC-U, which have limited long term experiences

in use, compared to rigid systems are considered

“high-risk”. Therefore, to compensate, high

“factors of safety” are incorporated into their

structural design calculations.

However, on the other hand, rigid systems

which have actual long term experiences are

considered “safe” and thus, relatively low

“factors of safety” are used by engineers, since

accepted long term experiences can always be

referred to.

Flexible systems manufactured from PVC-U

have been in common use as buried pipelines

for more than 30 years, with well documented

results. However, they have still not reached

the same degree of general acceptance among

engineers, compared to rigid materials.

From a technical-scientific point of view,

flexible pipes have been the subject of significant

research and development within major

institutions worldwide. Additionally, their

behaviour patterns in situ have also been studied

over a number of years resulting in a close

correlation of the results between the theoretical

and the practical. Furthermore, based on the

above research it can be established that flexible

systems can now offer engineers a minimum

design life in excess of 50 years.

With this as a background it seems

unsatisfactory from both a social and economical

point of view, that the use of flexible systems are

not as widespread as their merits justify.

The plastic industry is aware of the fact that

one reason why engineers are reluctant to accept

the use of flexible systems is the absence of

an authoritative document which covers the

structural design of the system.

The purpose of this publication is to try and

remedy this by detailing within the following

sections all the necessary design criteria, relating

to the design and installation of Osma UltraRib,

which is a structured wall, PVC-U, flexible sewer

system.

O S M A U L T R A R I B S Y S T E M 2Introduction Continued


Externa l re in forc ing r ibs g iveexcept iona l ax ia l r ig id i tyand rad ia l s t rength

Concent r i c ex te rna lre in forc ing r ibs

E las tomer icSea l ing R ing

Improved hydrau l ic f low due to the smoothin terchange between p ipe and f i t t ings

The unique Ul t raRib h igh per formance jo int

O S M A U L T R A R I B S Y S T E M3Pipe Technology and Joint Design


2. MATERIAL

The strength and performance qualities of PVC-U

have been studied for a number of years to assess

the materials’ long-term characteristics. Research

has proven its suitability for the

manufacture of large diameter drainage and

sewerage systems, since it becomes an intrinsic

part of the ground during settlement. This fact

paved the way for a new development in pipe

technology, not only in terms of manufacturing

but also in the structural properties of the pipe

itself i.e. Osma UltraRib.

3. THE OSMA ULTRARIB SYSTEM

Osma UltraRib is a fully socketed system of

pipe and fittings which combines secure jointing

with ease of installation. The pipe has a smooth

inner surface and externally has a repeating

pattern of concentric ribs which gives the pipe

its exceptional axial rigidity and enhanced radial

strength.

Osma UltraRib pipe and fittings are offered in

150mm, 225mm and 300mm diameters. Pipe is

manufactured to Water Industry Specification

(WIS) 4-31-05 and Kitemarked under the BSI

Certification Scheme. All Osma UltraRib fittings

are covered by a British Board of Agrément

Certificate.

3.1 Joint Design

Osma UltraRib joints are made by placing the

sealing ring between the second and third

external reinforcing ribs nearest the spigot end of

the pipe, which is then inserted into a socket.

The result is a high performance, water-tight

joint with two added benefits:

• No chamfering of the pipe ends.

• Ring displacement during installation is impossible.

3.2 Fitting Design

The majority of Osma UltraRib fittings are socketed

to provide total flexibility in use and to reduce

installation time on site. Each Osma UltraRib

component has concentric, external reinforcing

ribs throughout its body section. The sockets of

the components are specially designed to allow

the pipe and socket of the fitting to move as one

should differential settlement occur.

4. STANDARDS4.1 British Standards Institution

Osma UltraRib pipe complies with the followingrequirements and is Kitemarked:

WIS 4-31-05 - Specification for Solid Wall(1991 Issue 2) Concentric External Rib -

Reinforced uPVC Sewer Pipe.

4.2 British Board of Agrément

Osma UltraRib systems have been awarded thefollowing certificates:

98/3472 - UltraRib Gravity Sewer System - 150mm, 225mm and 300mm

91/58 - Roads and BridgesUltraRib Gravity Drainage andSewerage System - 150mm

89/46 - Roads and Bridges UltraRibGravity Sewerage System -225/300mm

5. ACCEPTANCE

Osma UltraRib systems are included in the fol-

lowing publications:-

• Sewers for Adoption, 4th Edition, under its

generic name Solid Wall, Concentric External

Rib - Reinforced uPVC Sewer Pipe.

• Civil Engineering Specification for the Water

Industry, under its generic name Solid Wall,

Concentric External Rib-Reinforced uPVC

Sewer Pipe.

• Specification for Highway Works, series 500

Drainage and Service Ducts.

• Standard Specification for Water and Sewerage

Schemes, Third Edition under its generic name

Solid Wall, Concentric External Rib -

Reinforced uPVC Sewer Pipe.

O S M A U L T R A R I B S Y S T E M 4Material, The Osma UltraRib System, Standards and Acceptance


Propor t iona l depths, ve loc i t ies and d ischarge graph

1 . 0

0 . 9

0 . 8

0 . 7

0 . 6

0 . 5

0 . 4

0 . 3

0 . 2

0 . 1

0 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5 0 . 6 0 . 7 0 . 8 0 . 9 1 . 0 1 . 1 1. 2

Prop

orti

onal

dep

th

P ropor t iona l ve loc i ty and d ischarge

0 . 8 1

0 . 9 4Q max

V max

Discharge( Q )

Ve loc i t y( V )

D

d

Propor t iona l depth=dD

O S M A U L T R A R I B S Y S T E M5Hydraulic Design


6. HYDRAULIC DESIGN-FOUL WATER SEWER

Recommendations as laid out in “Sewers for

Adoption 4th Edition” covering the hydraulic

design of foul sewers are as follows:

6.1 Flow Rates

Residential Developments

The design flows for gravity sewers should be –

4000 l/unit dwelling/day.

Industrial and Commercial Development

Design flow including domestic element, should

be agreed after discussion with the Undertaker/

Council.

6.2 Velocity

To provide a self-cleansing regime within foul

gravity sewers, the minimum velocity should

be 0.75 m/sec at one-third design flow. This

requirement will be deemed to be satisfied by a

150 mm nominal internal diameter gravity sewer

having a gradient not flatter than 1 in 150 and

at least 10 connected dwelling units.

These ‘deemed to satisfy’ parameters are not

to be taken as a norm when the topography

permits steeper gradients. Hydraulic studies

indicate that these requirements do not

necessarily achieve a self-cleansing regime.

When a choice has to be made between gravity

sewerage and pumped sewerage these criteria

should not be regarded as inflexible and the

Developer should consult the Undertaker/

Council.

6.3 Roughness Value – ks

The roughness value for foul gravity sewer design

should be 1.5mm.

7. HYDRAULIC DESIGN - SURFACE WATERSEWER

Recommendations as laid out in “Sewers for

Adoption 4th Edition” covering the hydraulic

design of surface water sewers are as follows:

7.1 Design Method

The appropriate method in the Wallingford

Procedure should be used unless otherwise

agreed with the Undertaker/Council e.g. in the

case of small developments.

7.2 Velocity

The minimum velocity should be 1m/sec at pipe

full flow.

7.3 Roughness Value – ks

The roughness value for surface water sewer

design should be 0.6 mm.

7.4 Flow Rates

The flow rates contained in the sizing tables

(see Table 1 pages 13 and 14) for Osma UltraRib

pipes from 150mm to 300mm diameter are based

on the Colebrook White formula expressed in the

form of:

ks + 2.51v V = -2√ (2gDS)

Log10 3.7D D√2gDS

V = Velocity (m/s)

g = Gravitational acceleration (m/s2)

D = Internal diameter of pipe (m)

S = Hydraulic gradient

ks = Roughness value (m)

v = Kinematic viscosity of fluid1.3 x 10-6 (m2/s)

O S M A U L T R A R I B S Y S T E M 6Hydraulic Design - Foul and Surface Water Sewer


8. STRUCTURAL DESIGN

This section is extensively based on the Water

Research Centre’s Engineering Report ER201E

“Guide to the Water Industry for the Structural

Design of Underground Non-Pressure PVC-U

Pipelines” and WIS 4-31-05.

8.1 Design Principles

Osma UltraRib derives its load bearing capacity

from its bedding and sidefill material. Under soil

and superimposed loading, the pipe will deform

vertically and horizontally developing the passive

support of sidefill. Consequently the design of

any Osma UltraRib pipeline must take into

account the interaction between the pipe and it’s

bedding and sidefill material.

As the soil and pipe interaction takes place,

deformation occurs. The present United Kingdom

Water Industry long-term deformation limit for

PVC-U pipelines is 6% of the vertical nominal

diameter of the pipe under consideration.

Practical experience shows that any increase in

deformation after a period of two years will be

negligible for a pipeline installed in accordance

with this guide.

8.2 Deformation Calculations

The long term deformation of PVC-U pipes under

load may typically be calculated using the

Spangler “lowa” formula which takes the form:

Deformation α Vertical load on pipePipe stiffness term + soil stiffness term

More specifically the long term deformation is given by:–

∆L

=(DL Po + Pt) Kx

(8SL) + (0.061 E')

Where

∆ L is the long term (50years) vertical deformation m

Po is the vertical soil load on the pipe N/m

Pt is the traffic load on the pipe N/m

Kx is a bedding constant (dimensionless)

SL is the long term stiffness of the pipe N/m2

E' is the modulus of soil reaction N/m2

DL is the deflection lag factor (dimensionless)

The deformation as a percentage is given by:

∆ x 100D

Where

∆ is the deformation at any time m

D is the mean diameter of the pipe m

An explanation of the various terms used in the

deformation equations is given below:

∆ L The deformation is the change in the vertical

mean diameter of the pipe.

D The mean pipe diameters are

Nominal MeanPipe Diameter Pipe Diameter

0.150m 0.161m

0.225m 0.238m

0.300m 0.317m

DL The deflection lag factor is a variable

dimensionless factor which takes account of

long term settlement of the bedding and

backfill. It is recommended that a value of not

less than 1.5 be given to DL for most normal

circumstances where granular material is

specified for the pipe bedding and pipe zone

backfill. This is a conservative value for most

installations and this value has been generally

adopted after being shown to have wide

validity.

Po The vertical load on the crown of the pipe due

to bedding and backfill material is normally

calculated by means of the simple

relationship;

Po = γgH Bc

Where:γ is the saturated bulk density of the backfill kg/m

3

H is the depth of cover over the pipe m

Bc is the outside diameter of the pipe m

(refer to Table 3, page 15).

g is the gravitational constant 9.81m/s2

O S M A U L T R A R I B S Y S T E M7Structural Design


Values of Po are given in Table 3 for various

sizes of pipes and depths of cover. Table 3

assumes a value for γ of 2,000 kg/m3 and this

should be used unless appropriate alternative

values have been obtained by site testing. It

will be recognised that the equation gives the

weight of the column of soil above the plan

area of the pipe. The soil column approach is

generally recognised as giving the most

conservative estimate of soil loads acting on

buried flexible pipes. The concept of wide and

narrow trenches as applied to rigid pipe design

has not been adopted in this guide, which is in

line with the approach adopted in ER201E.

Pt Traffic loads on buried pipes are given in Table

3. They are derived from tables used for the

structural design of rigid pipes. It has been

suggested that flexible pipes may be less

affected by passing traffic than rigid pipes but

as yet there is insufficient evidence to allow a

reduction in the values given in Table 3.

Kx The bedding constant reflects the quality of the

bedding and hence the amount of support given

to the pipe. A range of values was determined

theoretically by Spangler but is now customary

to use a nominal value for Kx of 0.103.

SL The long term stiffness. The nominal 50 year

stiffness of Osma UltraRib pipe shall be not

less than 3.0 kN/m2. As per test type

requirements stated in WIS 4-31-05.

E' The modulus of soil reaction broadly reflects

the quality of the material used for the pipe

bedding and the effectiveness of compaction.

Recommended values for E' are given in Table

2. Values of E' have been deduced empirically

and cannot be obtained by direct measurement.

8.3 Deformation Calculations - worked

example

The expected long term deformation for Osma

UltraRib pipes at depths of cover between 1.2

metres and 10 metres can be read directly from

Table 4, page 16. Below is a worked example

showing the method of calculation that the

results in Table 4 were derived from:

- Osma UltraRib Pipe nominal diameter 225mm

- Cover Depth 3.5m

- Main Road Loading

- Soil Bulk Density 2,000 kg/m3

- Bedding Material - Graded Gravel - Compacted

∆ L = (DL Po + Pt) Kx

(8SL ) + (0.061 E')

Where

DL = 1.5

Po = γgHBc

= 2000 x 9.81 x 3.5 x 0.25

= 17,168 N/m (17.2 kN/m or refer to Table 3)

Pt = 5.3 kN/m (from Table 3)

Kx = 0.103

SL = 3.0 kN/m2

E' = 10 MN/m2 (10,000 kN/m2)

∴∆ L = (1.5 x 17.2 + 5.3) 0.103(8 x 3) + (0.061 x 10,000)

= 31.1 x 0.10324 + 610

= 3.2033634

= 0.00505 m

To calculate % deformation divide by the mean

pipe diameter (D) and multiply by 100.

= 0.00505 x 1000.238

= 2.12%

Therefore the long term deformation for the above

example would be 2.12%.

O S M A U L T R A R I B S Y S T E M 8Structural Design continued


Time-deformation curve

Interaction between pipe, bedding and sidefill

0

1year 2 yearsTime after installation

Pipe

def

orm

atio

n

50 years

Settlementdeformation

Main backfill zone

Initial backfill zone

DN + 300

Pt Pt Pt

Po

Sidefill zone

Bedding zone100mm

150mm

H

Installationdeformation

O S M A U L T R A R I B S Y S T E M9Structural Design continued


8.4 Buckling Calculations

The purpose of carrying out buckling calculations

is to ensure that the critical buckling pressure

(Pcr) for a buried pipe exceeds the actual imposed

buckling pressure (Pb) by an adequate margin. It

is recommended that a factor of safety of 2.5 be

adopted. The imposed buckling pressure (Pb) is

determined by considering the net external loads

on the pipe.

Pb = Po + Pt

Bc

The critical buckling pressure is given by the

following formula which takes account of the

modulus of soil reaction and the long term pipe

stiffness:

Pcr = √ 32 E' SL

This is usually modified by the introduction of a

reduction factor Rd. This recognises that as the pipe

is deformed the critical buckling pressure reduces.

Within the deformation limits recommended in

this guide a relationship of the following form is

normally considered valid:

Rd = 1 – 3 ∆ L

D

Thus

Pcr = Rd √ 32 E' SL

Introducing the factor of safety against buckling

leads to the formula:

Pcr ≥ 2.5Pb

8.5 Buckling Calculations - worked

example.

The buckling calculations safety factor for Osma

UltraRib pipes at depths of cover between 1.2m

and 10m can be read directly from table 4 on

page 16. Below is a worked example showing the

method of calculating the results shown in table

4.

Installation as per deformation calculations

worked example:

Pb =Po + Pt

Bc

=17.2 + 5.30.25

= 90 kN/m2

Rd = 1 – 3 ∆ L

D

= 1 – (3 x 0.0212)

= 0.9364

Pcr = Rd √ 32 E' SL

= 0.9364 √ 32 x 10,000 x 3

= 917.5 kN/m2

Pcr = 917.5 = 10.19Pb 90.0

∴ The critical buckling pressure (Pcr) is 10.19

times greater than the imposed buckling pressure

and exceeds the minimum safety factor of 2.5.

O S M A U L T R A R I B S Y S T E M 10Structural Design continued


DN= Nominal diameter= Vertical deformation

Osma UltraRib’s unique design restricts deformation under loadsD

ND

N

∆

∆

L

LMaximum UK deformation 6%

O S M A U L T R A R I B S Y S T E M11Structural Design continued


9.0 PROTECTION OF PIPES UNDER ROADS

The following recommendations as laid down in

“Sewers For Adoption, 4th Edition”, Clauses 2.7,

4.3.4, 4.5.2, 4.5.3 and 4.5.4 should be followed.

The following are extracts from selected clauses

taken from “Sewers for Adoption - 4th edition”.

Please refer to the document for the full

recommendation.

9.1 Depths of Sewers - Clause 2.7

Sewers laid within highways should have a

minimum cover of 1.2m measured from the top

of the pipe barrel to the finished road surface, in

order to avoid interference with other

underground utility pipes and cables. Where this

is not practicable, special protective measures

may be required. The design of the pipeline

should take account of loading from the passage

of the Developer’s construction plant as well as

normal design loading.

9.2 Backfilling - Clause 4.3.4

Filling material shall be deposited in layers not

exceeding 225mm unconsolidated thickness, and

then fully compacted to form a stable backfill.

Where the excavation is within 1m of the edge of

the carriageway, or proposed carriageway, the fill

material shall be such as to permit adequate

drainage. Where the excavations have been

supported and the supports are to be removed,

these, where practicable, shall be withdrawn

progressively as backfilling proceeds in such a

manner as to minimise the danger of collapse and

all voids formed behind the supports shall be

carefully filled and compacted.

9.3 Pipe Bedding - Clause 4.5.2

Bedding for pipes shall be constructed by

spreading and compacting granular bedding mate-

rial over the full width of the pipe trench. After

the pipes have been laid, additional granular

material shall, if required, be placed and

compacted equally on each side of the pipes and

where practicable, this shall be done in sequence

with the removal of the trench supports.

9.4 Concrete Protection to Pipes - Clause

4.5.3

Concrete provided as a protection to pipes shall

be Grade C20 placed to the required depth in one

operation. Where pipes with flexible joints are

used, concrete protection shall be interrupted

over its full cross-section at each pipe joint by a

shaped compressible filler.

Where pipes are protected by a concrete

cover slab placed above the pipe this shall extend

across the full width of the trench and there shall

be a minimum of 150mm of surround between

the crown of the pipe and underside of the slab.

9.5 Completion of Pipe Surround - Clause

4.5.4

After completion of the relevant operations in

Clauses 4.5.1, 4.5.2 and 4.5.3, fill material shall,

where required, be placed and compacted over

the full width of the trench in layers not exceeding

150mm before compaction, to a finished thickness

of 250mm above the crown of the pipes.

Subsequent backfilling shall then be carried out

as specified in Clause 4.3.4.

O S M A U L T R A R I B S Y S T E M 12Protection of Pipes under Roads


Table 1. Osma UltraRib Pipe Sizing Tables

Size 150 Size 225 Size 300Mean Bore 151.8mm Mean Bore 225.6mm Mean Bore 300.2mm

k values in mm k values in mm k values in mmGradient 0.60 1.50 0.60 1.50 0.06 1.50

1:10 l/s 58.421 50.724 166.587 145.782 353.909 311.317m/s 3.228 2.803 4.167 3.647 5.000 4.398

1:20 l/s 41.232 35.835 117.621 103.013 249.942 220.009m/s 2.278 1.980 2.942 2.577 3.531 3.108

1:30 l/s 33.617 29.239 95.929 84.065 203.884 179.558m/s 1.857 1.616 2.400 2.103 2.881 2.537

1:40 l/s 29.078 25.307 82.999 72.770 176.430 155.444m/s 1.607 1.398 2.076 1.820 2.493 2.196

1:50 l/s 25.981 22.624 74.175 65.062 157.694 138.989m/s 1.436 1.250 1.856 1.628 2.228 1.964

1:55 l/s 24.760 21.566 70.696 62.023 150.307 132.501m/s 1.368 1.192 1.769 1.552 2.124 1.872

1:60 l/s 23.695 20.644 67.662 59.373 143.865 126.842m/s 1.309 1.141 1.693 1.485 2.033 1.792

1:65 l/s 22.755 19.829 64.985 57.034 138.180 121.849m/s 1.257 1.096 1.626 1.427 1.952 1.722

1:70 l/s 21.918 19.104 62.600 54.951 133.177 117.401m/s 1.211 1.056 1.566 1.375 1.881 1.659

1:75 l/s 21.166 18.453 60.458 53.079 128.568 113.406m/s 1.170 1.020 1.521 1.328 1.816 1.602

1:80 l/s 20.486 17.863 58.520 51.386 124.453 109.791m/s 1.132 0.987 1.464 1.286 1.758 1.551

1:85 l/s 19.867 17.327 56.756 49.845 120.707 106.501m/s 1.098 0.957 1.420 1.247 1.705 1.505

1:90 l/s 19.300 16.836 55.141 48.434 117.277 103.488m/s 1.066 0.930 1.379 1.212 1.657 1.462

1:95 l/s 18.778 16.384 53.655 47.136 114.122 100.717m/s 1.038 0.905 1.342 1.179 1.612 1.423

1:100 l/s 18.297 15.966 52.282 45.936 111.207 98.156m/s 1.011 0.882 1.308 1.149 1.571 1.387

1:105 l/s 17.850 15.579 51.008 44.823 108.503 95.780m/s 0.986 0.861 1.276 1.121 1.533 1.353

1:110 l/s 17.433 15.218 49.823 43.787 105.985 93.568m/s 0.963 0.841 1.246 1.095 1.497 1.322

1:115 l/s 17.045 14.881 48.715 42.820 103.633 91.502m/s 0.942 0.822 1.219 1.071 1.464 1.293

1:120 l/s 16.681 14.566 47.678 41.913 101.430 89.567m/s 0.922 0.805 1.193 1.049 1.433 1.265

1:125 l/s 16.338 14.269 46.703 41.062 99.360 87.749m/s 0.903 0.788 1.168 1.027 1.404 1.240

1:130 l/s 16.016 13.990 45.785 40.260 97.411 86.036m/s 0.885 0.773 1.145 1.007 1.376 1.216

1:135: l/s 15.712 13.727 44.919 39.503 95.572 84.420m/s 0.868 0.758 1.124 0.988 1.350 1.193

1:140 l/s 15.425 13.477 44.099 38.787 93.831 82.892m/s 0.852 0.745 1.103 0.970 1.326 1.171

1:145 l/s 15.152 13.241 43.323 38.108 92.182 81.443m/s 0.837 0.732 1.084 0.953 1.302 1.151

1:150 l/s 14.893 13.017 42.585 37.463 90.616 80.067m/s 0.823 0.719 1.065 0.937 1.280 1.131

1:155 l/s 14.647 12.804 41.884 36.850 89.126 78.758m/s 0.809 0.707 1.048 0.922 1.259 1.113

O S M A U L T R A R I B S Y S T E M13Pipe Sizing Tables


Table 1. Osma UltraRib Pipe Sizing Tables continued

Size 150 Size 225 Size 300Mean Bore 151.8mm Mean Bore 225.6mm Mean Bore 300.2mm

k values in mm k values in mm k values in mmGradient 0.60 1.50 0.60 1.50 0.60 1.50

1:160 l/s 14.413 12.600 41.215 36.266 87.707 77.511m/s 0.796 0.696 1.031 0.907 1.239 1.095

1:165 l/s 14.189 12.406 40.577 35.709 86.353 76.321m/s 0.784 0.685 1.015 0.893 1.220 1.078

1:170 l/s 13.975 12.221 39.968 35.176 85.059 75.184m/s 0.772 0.675 1.000 0.880 1.202 1.062

1:175 l/s 13.770 12.043 39.385 34.667 83.820 74.096m/s 0.761 0.665 0.985 0.867 1.184 1.047

1:180 l/s 13.574 11.874 38.826 34.179 82.634 73.054m/s 0.750 0.656 0.971 0.855 1.167 1.032

1:185 l/s 13.386 11.711 38.291 33.711 81.496 72.054m/s 0.740 0.647 0.958 0.843 1.151 1.018

1:190 l/s 13.206 11.554 37.776 33.261 80.404 71.094m/s 0.730 0.638 0.945 0.832 1.136 1.004

1:195 l/s 13.032 11.404 37.282 32.829 79.354 70.172m/s 0.720 0.630 0.933 0.821 1.121 0.991

1:200 l/s 12.865 11.259 36.806 32.413 78.343 69.284m/s 0.711 0.622 0.921 0.811 1.107 0.979

1:210 l/s 12.549 10.985 35.906 31.626 76.431 67.604m/s 0.693 0.607 0.898 0.791 1.080 0.955

1:220 l/s 12.255 10.730 35.068 30.894 74.651 66.040m/s 0.677 0.593 0.877 0.773 1.055 0.933

1:230 l/s 11.981 10.492 34.285 30.209 72.989 64.579m/s 0.662 0.580 0.858 0.756 1.031 0.912

1:240 l/s 11.723 10.269 33.551 29.568 71.432 63.211m/s 0.648 0.567 0.839 0.740 1.009 0.893

1:250 l/s 11.482 10.059 32.863 28.966 69.969 61.925m/s 0.634 0.556 0.822 0.725 0.989 0.875

1:260 l/s 11.254 9.862 32.214 28.399 68.591 60.715m/s 0.622 0.545 0.806 0.710 0.969 0.858

1:270 l/s 11.039 9.676 31.602 27.864 67.291 59.572m/s 0.610 0.535 0.791 0.697 0.951 0.842

1:280 l/s 10.836 9.499 31.023 27.358 66.061 58.491m/s 0.599 0.525 0.776 0.684 0.933 0.826

1:290 l/s 10.643 9.332 30.474 26.878 64.895 57.467m/s 0.588 0.516 0.762 0.672 0.917 0.812

1:300 l/s 10.461 9.174 29.952 26.422 63.788 56.494m/s 0.578 0.507 0.749 0.661 0.901 0.798

1:400 l/s 9.028 7.931 25.869 22.851 55.114 48.870m/s 0.499 0.438 0.647 0.572 0.779 0.690

1:500 l/s 8.051 7.083 23.083 20.415 49.196 43.667m/s 0.445 0.391 0.577 0.511 0.695 0.617

1:600 l/s 7.330 6.457 21.027 18.616 44.829 39.827m/s 0.405 0.537 0.526 0.466 0.633 0.563

1:700 l/s 6.770 5.970 19.430 17.218 41.436 36.843m/s 0.374 0.330 0.486 0.431 0.585 0.521

1:800 l/s 6.318 5.578 18.142 16.092 38.701 34.437m/s 0.349 0.308 0.454 0.403 0.547 0.487

1:900 l/s 5.945 5.254 17.077 15.159 36.436 32.445m/s 0.328 0.290 0.427 0.379 0.515 0.458

1:1000 l/s 5.629 4.979 16.175 14.370 34.521 30.759m/s 0.311 0.275 0.405 0.359 0.488 0.435

O S M A U L T R A R I B S Y S T E M 14Pipe Sizing Tables continued


Notes

1.Table 3 defines the values of the soil loads, Po, for

the various pipe outside diameters and depths of

cover under consideration in this Guide. A

saturated bulk density value of 2000kg/m3

is

assumed. Should the site conditions differ from

this, then the values given should be factored

accordingly.

2.Table 3 defines the values of the traffic loads, Pt,

for outside diameters and depths of cover under

consideration in this Guide. These values have

been taken from “A Guide to Design Loadings for

Buried Rigid Pipes” produced by the Department of

Transport.

Table 3. Transmitted Loads to Osma UltraRib Pipe

Size Outside Type of Load Transmitted Load kN/m for Depth in metresDiameter Bc Depth of

mm mm Cover (H) 0.9m 1.2m 1.5m 2.0m 2.5m 3.0m 3.5m 4.0m 4.5m 5.0m

150 170 Soil (Po) 3.0 4.0 5.0 6.7 8.3 10.0 11.7 13.3 15.0 16.7

Main Rd (Pt) 14.9 11.4 9.2 7.2 5.8 4.6 4.0 3.4 2.9 2.5

225 250 Soil (Po) 4.4 5.9 7.4 9.9 12.3 14.3 17.2 19.7 22.1 24.6

Main Rd (Pt) 19.8 15.1 12.1 9.5 7.7 6.2 5.3 4.5 3.8 3.2

300 335 Soil (Po) 6.0 7.9 9.9 13.2 16.5 19.8 23.0 26.3 29.6 37.9

Main Rd (Pt) 29.3 27.3 18.3 14.2 11.5 9.2 7.9 6.6 5.5 4.7

Depth ofCover (H) 5.5m 6.0m 6.5m 7.0m 7.5m 8.0m 8.5m 9.0m 9.5m 10.0m

150 170 Soil (Po) 18.3 20.0 21.7 23.3 25.0 26.7 28.4 30.0 31.7 33.4

Main Rd (Pt) 2.0 1.8 1.6 1.4 1.2 1.1 1.0 0.9 0.8 0.7

225 250 Soil (Po) 27.0 29.5 31.9 34.4 36.8 39.3 41.7 44.2 46.4 49.1

Main Rd (Pt) 2.7 2.4 2.1 1.8 1.6 1.5 1.4 1.3 1.2 1.1

300 335 Soil (Po) 36.2 39.5 42.8 46.0 49.3 52.6 55.9 59.2 62.5 65.8

Main Rd (Pt) 4.0 3.5 3.0 2.7 2.3 2.2 2.0 1.8 1.6 1.4

Table 2. Typical Modulus ValuesTypical modulus values for processed bedding and sidefill materials for use in flexible pipeline design.

MaterialModulus of Soil Reaction E' (MN/m2)

Degree of compaction

Description Casagrande symbol Uncompacted 90% Modified ProctorSee note (b) See note (a)

Gravel Single-sized GPu 5 10

Gravel graded GW 3 10

Notes: (a) BS 1377, ‘Determination of the dry density/moisture content relationship (4.5 kg rammer method)’, is used to determine the Modified Proctor Density.(b) GPu – Poorly graded uniform gravel GW – Well graded gravel

O S M A U L T R A R I B S Y S T E M15Structural Design Tables


The above table is based on the following

assumptions.

a) Main road traffic loading is expected.

b) Degree of Compaction = 90% Modified

Proctor, this is generally achieved with 1 pass of

a Mechanical Plate Compactor (as per Table 5 of

ER201E).

c) Single sized or graded gravel in accordance

with WIS 4-08-01 1994 : issue 4 is used for pipe

bed & surround.

d) The pipework is installed in accordance with

the requirements of “Sewers for Adoption 4th

Edition”.

Deformation should not exceed 6%.

Buckling Safety Factor should exceed 2.5.

Table 4. Pipe Deformation Table

150mm 225mm 300mm

DEPTH % BUCKLING % BUCKLING % BUCKLING(m) DEF. SAFETY FACTOR DEF. SAFETY FACTOR DEF. SAFETY FACTOR

1.2 1.75 10.28 1.63 11.10 1.75 10.29

1.3 1.73 10.55 1.62 11.39 1.73 10.54

1.4 1.71 10.83 1.60 11.69 1.71 10.80

1.5 1.69 11.13 1.58 12.00 1.69 11.08

1.6 1.70 11.18 1.59 12.01 1.70 11.14

1.7 1.71 11.24 1.61 12.02 1.70 11.32

1.8 1.72 11.29 1.62 12.03 1.72 11.26

1.9 1.73 11.35 1.64 12.04 1.73 11.32

2 1.74 11.40 1.66 12.05 1.74 11.38

2.25 1.79 11.28 1.72 11.84 1.79 11.25

2.5 1.84 11.17 1.78 11.64 1.85 11.12

2.75 1.91 10.93 1.85 11.34 1.92 10.88

3 1.98 10.70 1.93 11.05 1.99 10.66

3.25 2.08 10.30 2.03 10.61 2.08 10.28

3.5 2.17 9.92 2.12 10.19 2.17 9.93

3.75 2.27 9.58 2.22 9.82 2.26 9.60

4 2.36 9.26 2.32 9.47 2.36 9.29

4.5 2.56 8.60 2.52 8.75 2.56 8.63

5 2.78 7.98 2.73 8.10 2.77 8.01

5.5 2.98 7.44 2.95 7.52 2.98 7.44

6 3.22 6.89 3.18 6.96 3.21 6.91

6.5 3.45 6.42 3.41 6.47 3.44 6.44

7 3.68 5.99 3.64 6.03 3.67 6.00

7.5 3.91 5.61 3.88 5.64 3.91 5.61

8 4.15 5.25 4.12 5.27 4.15 5.25

8.5 4.39 4.93 4.37 4.94 4.39 4.93

9 4.64 4.64 4.61 4.64 4.64 4.64

9.5 4.88 4.38 4.86 4.38 4.88 4.38

10 5.12 4.14 5.10 4.14 5.12 4.14

O S M A U L T R A R I B S Y S T E M 16Structural Design Tables continued

O S M A U L T R A R I B P R O D U C T M A N U A L

All OSMA systems are backed by fulltechnical literature and project support.See inside back cover for details.

UR

101

Wavin Plastics LimitedParsonage Way Chippenham Wiltshire SN15 5PN

Tel: 01249 766600Fax: 01249 443286

Email: [email protected]

Wavin Plastics Limited operates a programme of continuous product development, and therefore reserves the right to modify or amend the specification of their products without notice. All information in this publication is given ingood faith, and believed to be correct at the time of going to press. However, no responsibility can be accepted forany errors, omissions or incorrect assumptions. Users should satisfy themselves that products are suitable for thepurpose and application intended.

ISO 9001:2000

Meeting your needsBelow Ground Drainage systems, developed by Wavin Plastics Limited,form part of a comprehensive range of systems to provide intelligent solutions for all building, construction and utilities projects.

These include:

Above Ground ProjectsOSMA Rainwater systems

OSMA Soil & Waste systems

Plumbing & Heating ProjectsOSMA Flexible Plumbing systems

OSMA Underfloor Heating systems

Below Ground ProjectsOSMA Below Ground Drainage systems

OSMA Water Management systems

OSMA Ducting systems

Pressure Pipe ProjectsOSMA Pressure Pipes for Water

OSMA Pressure Pipes for Gas

All OSMA systems are backed by fulltechnical literature and project support.

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