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Tech Profiles > Trenchless Installation

Trenchless Installation

HOBAS pipe trenchless installations include sliplining rehabilitation, pipe bursting, direct jacking, microtunneling and secondary tunnel lining (water-way carrier) applications. HOBAS pipes provide many cost saving benefits to the user and installer, regardless of the installation method; however, several unique attributes are ideally and inherently suited to trenchless installation methods. In fact, HOBAS pipes have been so successful in these applications that they have earned the label of “Premier Trenchless Pipe.” Installations Definitions:

Sliplining Rehabilitation:
A process whereby a deteriorated pipeline is lined (or relined) with a new pipe of a smaller diameter to refurbish the original pipe for continued service.

Direct Jacking:
A tunneling process whereby a single new pipe is installed in one pass. A bore head begins the tunnel excavation from an access shaft and is pushed along by hydraulic jacks that remain in the shaft. The link to the boring head is maintained by adding jacking pipe between the jacks and the head. By this procedure, the pipe is laid as the tunnel is bored.
Microtunneling is defined as a trenchless construction method for installing pipelines. The North American definition of microtunneling describes a method and does not impose size limitations on such method; therefore, a tunnel may be considered a microtunnel if all of the following features apply to construction:

  • Remote Controlled: The microtunneling boring machine (MTBM) is operated from a control panel, normally located on the surface. The system simultaneously installs pipe as spoil is excavated and removed. Personnel entry is not required for routine operations.
  • Guided: The guidance system usually references a laser beam projected onto a target in the MTBM, capable of installing gravity sewers or other types of pipelines to the required tolerances, for line and grade.
  • Pipe Jacked: The pipeline is constructed by consecutively pushing pipes and the MTBM through the ground using a jacking system for thrust.
  • Continuously supported: Continuous pressure is provided to the face of the excavation to balance groundwater and earth pressures.
Tunnel Waterway Carrier:
The second lining (waterway carrier) in a two pass tunnel construction method.
Pipe Characteristics:
HOBAS pipes for trenchless installations are a corrosion resistant, centrifugally cast, glass-fiber reinforced polymer mortar, tubular product connected with push-together, rubber ring-sealed joints. The pipes and joints may be pressure or non-pressure rated depending on the required service.
The nominal diameter range is 18″ to 126″. Maximum section length is 20 ft. with standard shorts in even divisions available.
In all installations, HOBAS pipes are designed as semi-rigid, flexible conduits to withstand all loads without structural aid from old pipes (sliplining) or primary tunnel liners.
HOBAS fiberglass pipes provide many important, cost saving benefits to the user and installer. Some benefits are universal (apply regardless of installation method), while others are specific to trenchless applications.
Benefits Specific to Trenchless Installations:

  • Due to the segmented pipes, the sewer may be lined while in service (live), avoiding costly and risky by-pass pumping.
  • Lower pushing or jacking insertion loads due to the smooth, constant O.D. and lightweight straight pipe wall.
  • Fewer access pits needed due to the long pushes possible with high strength, smooth wall pipes.
  • Small access pits required.
  • Radius curves easily negotiated with the gasket-sealed joints.
  • Smaller primary tunnel (10 to 15%) and less excavation (20 to 30%) on two pass tunnels.
  • Fast liner insertion due to push-together joints and lightweight 20 ft. sections.
  • Easy to grout liners’ annular space due to high stiffness, low creep design.
  • High reliability and lower risk installations due to the composite material resiliency and the consistent, high quality generated by the computer controlled pipe manufacturing process.
HOBAS pipes’ many unique attributes provide installation and operation benefits unavailable with other materials. Use of HOBAS pipes in trenchless installations results in improved reliability, reduced risk, and lower costs. HOBAS pipes have truly earned the title of “Premier Trenchless Pipe.”

Copies of an article, “Success of Centrifugally Cast Fiberglass Pipes in Trenchless Installations,” that covers the topic in greater detail are available upon request.