Concrete pipe jacking is a method of installing pipelines without disrupting existing surface facilities or activities. With the increasing growth in South African cities and towns and the consequent need to refurbish, renew and upgrade existing services, pipe jacking is seen to be a growing industry. Although the basic methods of concrete pipe jacking are similar for all pipeline applications, South African contractors have developed their own individual tech-niques to achieve accuracy during jacking, to lengthen the jacking distance and to control varying ground conditions.
Concrete pipes are jacked from a jacking pit to a receiver pit usually located at a manhole or access chamber. The main jacks are installed in the jacking pit and are used to push the concrete pipes into the cavity excavated ahead of the progressing pipeline. The main jack capacity depends on the size of pipe, length of the line and the type of ground in which it is being jacked. There are typically two or four jacks with capacity of up to 300 tonnes.
The jacking forces are resisted by the thrust block in the jacking pit and applied to the pipeline end through the steel thrust ring. The concrete pipe end is protected against spalling by soft wood or woodchip joint packers between the thrust ring and the concrete surface. The steel cutting shield fitted to the lead pipe gives protection to workers and allows steering and alignment adjustments. Intermediate jacking stations may be required in long lengths and hard ground conditions. Alternatively bentonite injections may be used to reduce the friction between the pipes and the soil.
Pipeline alignment is continually monitored and adjusted during jacking by laser from the jacking pit to a target fixed to the inside crown of the lead pipe or shield. Gradual adjustments are continuously made to avoid over-stressing the concrete pipe joints.
|Jacking Class 100D - SABS 677 Type SC|
|(mm)||(ID mm)||(OD mm)||(T mm)||(mm x mm)||(mm)||(Kg/unit)|
|840 Butt||810||1034||112||50 x 10||2260||1878|
|900||880||1100||110||200 x 20||2500||2190|
|1050||1030||1250||110||200 x 20||2500||2523|
|1117||1117||1375||129||424 x 20||2260||2922|
|1200||1150||1390||120||200 x 20||2500||3065|
|1350||1350||1600||125||200 x 20||2500||3708|
|1473||1473||1780||154||560 x 20||2260||4540|
|1500||1460||1720||130||200 x 20||2500||4158|
|1800||1760||2120||180||200 x 20||2500 or 2300||7025|
|1880||1880||2236||178||756 x 20||200||5760|
|2000 Butt||2032||2432||200||80 x 12||2000||7000|
|2100||2100||2500||200||200 x 20||2000||7400|
|2350||2350||2950||300||200 x 20||2000||12795|
|2400||2400||2800||200||80 x 12||1000||4180|
|2500||2500||3000||250||200 x 20||1500 or 2440||13493|
Nominal length 2,5m.
Pipes available in half lengths by arrangement.
Details of larger diameter pipes available on request.
SI on request.
Dimensions and thus the mass of the pipes are subject to change without notice.
For details of pipes from any particularfactory, please contact our sales office.
All dimensions in mm.