2Introduction

Infraset manufactures reinforced concrete pipes using two well-known production processes: roller suspension and automated vertical casting using high strength, high durability concrete. Both these processes are used worldwide and are acknowledged to be ideal for concrete pipe manufacturing.

All the manufacturing processes are done under carefully controlled conditions using advanced technology and equipment. These processes provide flexibility for the manufacturing of tailormade wall thicknesses for special load and strength requirements.

If corrosion problems are anticipated, Infraset has several methods of prolonging the life of the concrete pipe. The substitution of the siliceous aggregates with calcareous aggregates results in the extended life of the concrete pipe. An HDPE liner can alter-natively be added to the bore of the pipe to prevent the sulphuric acids from coming into contact with the concrete surface.

CLASSIFICATION OF PIPES

Types of pipe

Infraset offers a large range of pipes readily available in nominal lengths of 2.5m and also half-lengths on special arrangement.

Pipes ranging from 300 to 1800 with Interlocking ogee joints, 300 to 1800 pipes with Spigot and Socket joints and 900 to 1800 pipes with In-the-Wall joints are all produced in three strength classes.

Jacking pipes are manufactured only in class 100D and vary in size from 840 to 2500. Stronger pipes capable of carrying higher D-loads are manufactured on request.

All Infraset pipes bear the SANS mark and are designed, manufactured and tested in accordance with SANS 677.

SC (Stormwater Culvert) pipes are manufactured with a non-watertight, interlocking ogee joint.

The sewer and irrigation (SI) pipes are manufactured using dolomitic aggregates and have a watertight Spigot and Socket or In-the-Wall joint. Sewer pipes with a sacrificial layer (WSL) are manufactured to the SABS 1200 LD requirements with an additional 15mm cover for pipes ranging from 300 to 1050 and 20mm for pipes 1200 1800. T2 and T4 pressure pipes, tested to 2 and 4 bar respectively are available on request.

Spigot and Socket and In-the-Wall joint pipes are joined and sealed using either a rolling rubber or a sliding rubber ring respectively. The sliding rubber ring is installed using a soft soap lubricant.

Types of joints

Interlocking Ogee Joint Spigot & Socket Joint Butt Joint In-the-Wall Joint

PRECAST CONCRETE PIPES TECHNICAL DATA

3Strength of pipes

Two strength tests are done on Infraset pipes. The first is a crushing test on both the SC and SI pipes, and the second is a hydraulic pressure test only on the SI pipes. The two edge-bearing crushing test is done to a proof load and also to an ultimate load 25% greater than the proof load. The proof load is determined by the class of pipe multiplied by the nominal diameter of the pipe. The proof load test can be defined as a line load that a pipe must resist without the development of crack widths exceeding 0.25mm over a length of more than 300mm. The ultimate load is the maximum line load that the pipe must support in the same test.

Load classifications

Note: D = Nominal Diameter in metres.Example: A 1500mm 75D pipe must resist: Proof Load = 75 x 1.5 = 113 kN/m Ultimate Load = 75 x 1.5 x 1.25 = 140 kN/m

All SI pipes are tested to 1,4 bar and passes the test if the pipe withstands the pressure for at least two minutes without any sign of leakage.

Loads on pipes

Working loads on pipes consist of primary and secondary loads. The primary loads that the pipes must carry are; the mass of earth fill above the pipe, traffic loading and internal pressures. The secondary loads result from soil movement and temperature effects that influence the pipe line. These secondary loads are accommodated by the flexible pipe joints.

Earth loads are determined using the Marston and Spangler theory and are dependant upon the type of installation, type of backfill material and height of fill. The two installation conditions are trench and embankment.

Traffic loads are dependant upon the wheel loads, spacing and contact areas, and the distribution of these through the fill. The standard traffic loads applicable to national highways are given in the TMH7: Code of practice for the design of highway bridges and culverts in South Africa. Infraset pipes are designed for a NB36 load, which equals an axle load of 360 kN or a 90 kN wheel load. The effective contact area of the load is a square of size 0.3m x 0.3m.

Bedding factor refers to the amount by which the bedding enhances the load-carrying capacity of the pipe. The bedding factor is defined as the ratio between the supporting strength of the buried pipe to the strength of the pipe as determined in the two-edge bearing test. The bedding of a pipe consists of a cradle of granular material underneath the pipe, which supports it and transfers the load to the foundation. Bedding factors are divided into four classes and are determined by the angle of support and type of the bedding material.

PRECAST CONCRETE PIPES TECHNICAL DATA

50D 50 x D 50 x D x 1.25 0.149 13.2 775D 75 x D 75 x D x 1.25 0.255 21.8 7

100D 100 x D 100 x D x 1.25 0.425 36.0 7

Wolf ACSR 18.13 0.726 69.2 37Bear ACSR 23.45 1.213 111.1 37

7/3.35 Steel 10.23 0.496 67.9 77/4.0 Steel 12.24 0.712 96.8 7

19/2.65 Steel 13.55 0.849 114 19

Class of Pipe Proof Load Ultimate Load Weight per m(kg/m)

Ultimate tensilestrength (kN)

Total strands

4PRECAST CONCRETE PIPES TECHNICAL DATA

A 2.8 3.8 120 13.2 7B 2.0 2.5 180 21.8 7C 1.5 2.0 90 36.0 7D 1.1 N/A 0 69.2 37

Bear ACSR 23.45 1.213 111.1 377/3.35 Steel 10.23 0.496 67.9 77/4.0 Steel 12.24 0.712 96.8 7

19/2.65 Steel 13.55 0.849 114 19

Class Trench Embankment Bedding Angle Ultimate tensilestrength (kN)

Total strands

Bedding Angle

Standard bedding classes and factors

Installation conditions

Trench condition occurs when the pipe is placed in a trench cut into natural ground level and then backfilled with suitable material.

Trench condition: Class-B Trench condition: Class-C

In the embankment condition the pipe is installed at ground level and is backfilled with suitable material.

Embankment condition: Class B Embankment condition: Class C

The following tables give the pipe strength requirements in terms of D-Loads for pipes laid in a trench condition, with trench widths as per SANS 1200DB, and in embankment condition, both with NB36 traffic loading. These tables meet the D-Load requirements for general site conditions.

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