Pipe Jacking Pdf

[Baudilio Eliason]

Pipejacking, generally referred to in the smaller diameters as microtunnelling, is a technique for installing underground pipelines, ducts and culverts. Powerful hydraulic jacks are used to push specially designed pipes through the ground behind a shield at the same time as excavation is taking place within the shield. The method provides a flexible, structural, watertight, finished pipeline as the tunnel is excavated.

There is no theoretical limit to the length of individual pipe jacks although practical engineering considerations and economics may impose restrictions. Drives of several hundred metres either in a straight line or to a radius or a series of radii are readily achievable. A range of mechanical and remote control excavation systems are available. Pipes in the range 150mm to 3000mm, can be installed by employing the appropriate system. Construction tolerances are comparable with other tunnelling methods, and the pipe jacking method generally requires less overbreak than alternative systems. It provides ground support and reduces potential ground movement. Mechanical excavation methods are similar to those employed in other forms of tunnelling. Shields, excavation and face support can be provided for a wide variety of ground conditions.

In order to install a pipeline using this technique, thrust and reception pits are constructed, usually at manhole positions. The dimensions and construction of a thrust pit vary according to the specific requirements of any drive with economics being a key factor. Pit sizes will vary according to the excavation methods employed, although these can be reduced if required by special circumstances.

A thrust wall is constructed to provide a reaction against which to jack. In poor ground, piling or other special arrangements may have to be employed to increase the reaction capability of the thrust wall. Where there is insufficient depth to construct a normal thrust wall, for example through embankments, the jacking reaction has to be resisted by means of a structural framework having adequate restraint provided by means of piles, ground anchors or other such methods for transferring horizontal loads.

To ensure that the jacking forces are distributed around the circumference of a pipe being jacked, a thrust ring is used to transfer the loads. The jacks are interconnected hydraulically to ensure that the thrust from each is the same. The number of jacks used may vary because of the pipe size, the strength of the jacking pipes, the length to be installed and the anticipated frictional resistance.

A reception pit of sufficient size for removal of the jacking shield is normally required at the completed end of each drive. The initial alignment of the pipe jack is obtained by accurately positioning guide rails within the thrust pit on which the pipes are laid. To maintain accuracy of alignment during pipe jacking, it is necessary to use a steerable shield, which must be frequently checked for line and level from a fixed reference. For short or simple pipe jacks, these checks can be carried out using traditional surveying equipment. Rapid excavation and remote control techniques require sophisticated electronic guidance systems using a combination of lasers and screen based computer techniques.

When the pipejack or microtunnel is carried out below the water table it is usual to incorporate a headwall and seal assembly within each thrust and reception pit. The use of these items prevents ingress of ground water and associated ground loss, and retains annular lubricants. The pipe jacking technique and its components have been subject to extensive and ongoing research at a number of leading UK universities including both Oxford and Cambridge. This has included model and full scale testing of pipes and joints and the effects of lubrication and soil conditioning on the pipe jacking process.

This activity has been undertaken under the auspices of the Pipe Jacking Association with funding and participation provided through government research bodies, water companies and the tunnelling and pipe jacking industry.

Pipe jacking is a trenchless construction method to install product pipe through the ground on line and grade for new service lines, sewer tunnels and utilities. Differing from the microtunneling method, pipe jacking requires personnel entry in the tunnel to operate equipment which limits typical installation diameters to 48-inch and above.

Pipe jacking is done from a launch shaft to a reception shaft with advancement provided by a hydraulic jacking frame located in the launch shaft. Excavation is controlled at the face by the operator as the forward shield or TBM is advanced via thrust forces transmitted by the jacking frame through the product pipe. Excavated material is transferred into specially designed haul units that carry the soil back to the launch shaft for removal at the surface. At the end of each prefabricated pipe segment, a new section of pipe is lowered into the launch containing necessary tunnel connections and connected for continued advancement.

Pipe Jacking Trenchless specializes in trenchless installations for power, communication, water, wastewater, storm drain, crude oil and natural gas. We have the equipment and personnel to tackle any sized job and handle any type of ground conditions.

Pipe Jacking Trenchless is an underground contractor that services every trenchless excavation market. We own a large inventory of pilot tube machines; auger bore machines; wheeled, shielded excavator, earth pressure balance (EPB) tunnel machines and excavating equipment ranging in diameters from 2-inch up to 144-inch.

Our capabilities range from high precision pilot tube installations and traditional auger boring installations to tunnel installations up to 12-feet in diameter as well as horizontal directional drilling and pit excavations.

Installation of 160 feet of 30-inch diameter natural gas transmission pipe located near the City of Indio in the Coachella Valley of California. The bore crossed under Interstate 10 with varying ground conditions which required us to switch back and forth from auger boring to hand mining to remove rocks and boulders which obstructed the bore path.

Installation of 300 feet of 42-inch diameter natural gas carrier pipe in a push and retrieve sequence using traditional auger boring with a hydraulic steering head for guidance. The project was completed in an environmentally sensitive area that required special procedures, monitoring, and documentation projects.

Shaft excavations, shoring, and the installation of two 110-inch diameter, 825-foot long rib and lag tunnels for two water lines and a sewer line of varying diameters to service a new semiconductor manufacturing facility. The project required day and night shifts with a wheeled tunnel boring machine (TBM) to progress through the caliche, rock, and cobble encountered along the tunnel horizon.

Installation of 1,056 feet of casing and sewer carrier in three drives using the guided boring method of installation, whereby pilot tubes are first installed then followed by a reamer and cased augers to complete the drive at the proper diameter. Following tunneling, high-density polyethylene (HDPE) sewer pipe was installed on spacers and pulled into the casing then tied in. Groundwater and substantial rain required continuous dewatering and removal of equipment from the pits every day to prevent equipment damage and impacts on the project.

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