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Search the ASTT technical archive.
Papers, case studies, standards and webinars covering trenchless methods across Australia and New Zealand.
459 results (298 ASTT documents, 161 ISTT technique descriptions) · showing 337–360
Float / Submersible
In partially filled pipes or tunnels, floating platforms can be used to allow the collection of inspection data above the waterline (using cameras and laser-based systems) as well as information about the profile of the base of the pipe/tunnel using sonar. It may also be possible to differentiate the surface outline…
ISTT
Flood Grouting
In the flood grouting method, a section of sewer system consisting of a mainline between two manholes, the manholes themselves and the laterals that connect to that mainline is sealed using a sequential flooding operation. First, the pipes within the section are cleaned and the section to be grouted is isolated using…
ISTT
Flow Quality (Chemical / Biological)
The presence of infiltration in significant quantities may alter the chemical and/or biological parameters in the wastewater stream within a sewer system offering an additional means of identifying the level of infiltration and helping to track down its sources.
ISTT
Flow Quantity Monitoring
Significant leakage in pressure pipe systems may be detected by discrepancies in flow monitoring data from the system. Such discrepancies may exist between the measured flow volume of treated water leaving a plant and the sum of metered volumes received by users or among different points of distributed metering.…
ISTT
Fold-and-Form
(Was also known as Deform-Reform) In this category are close-fit linings that use both heat and pressure to change the shape of the liner pipe to allow the installation to occur and then facilitate the expansion of the liner to fit tightly within the host pipe. Both modified PVC pipe formulations and polyethylene pipe…
ISTT
Fully-independent Rehabilitation
Since many of the methods listed as "renovation" techniques are capable of being designed to function independently of the existing host pipe, it is possible that such techniques can be considered to provide a "replacement" of the existing pipe. This possibility is recorded here but, for simplicity, all the renovation…
ISTT
Geochemical Survey
Geochemical surveys are used to look for chemical elements or materials in the groundwater or soil that could be detrimental to the installed pipes or other installed structures or present a health risk if they are released into the environment during construction or future operations. If polluted soil is found during…
ISTT
Geophysical Survey
An important category of non-invasive site investigation techniques involves geophysical survey methods. In addition to finding buried objects (as discussed under asset location), these methods can identify boundaries among soil and rock zones and infer some aspects of the geotechnical properties of those zones. The…
ISTT
Ground Investigation
Most of the methods identified here are part of typical site investigation work for any construction project that is dependent on ground conditions. Soil sampling requires boreholes or pits for the retrieval of samples but these represent small areas of disturbance relative to the ground surface traversed by most…
ISTT
Ground Penetrating Radar (GPR)
There are a wide range of techniques available to locate buried pipes. Most of these systems use electromagnetic waves or signals transmitted into the ground or from underground utilities. These technologies may be broadly classified as either electromagnetic or ground penetrating radar (GPR).Electromagnetic pipe…
ISTT
Groundwater Monitoring
Groundwater conditions at a site are important in both the design and construction of trenchless projects. Structurally, the groundwater level at a site controls the external groundwater pressure that will act on a pipe or installed liner. It also has an important impact on the provisions for face support in…
ISTT
Grout-in-Place Hose
In this category, a flexible liner is used that typically is made from a plastic sheet that is smooth on one side and with raised studs on the other side. The liner sheet is welded longitudinally to form a tube, then folded into a U-shape and pulled into the pipe to be renovated. When in position within the host pipe,…
ISTT
Horizontal Directional Drilling (HDD)
HDD is an extremely versatile trenchless technology that is used for the installation of everything from service connections to residences and buildings, to pipes and cables under roadways and rivers. HDD is best suited for installing pressure pipes and conduits where precise grades are not required. The main…
ISTT
Hybrid Methods
As the name implies, hybrid methods combine elements of two or more trenchless methods or otherwise enhance trenchless methods to improve performance or overcome particular site or job restrictions.
ISTT
Impact Moling
The impact mole or piercing tool is one of the oldest and simplest of the trenchless technologies. It is ideally suited for installation of small diameter pipes in compressible soils over short distances. Under suitable conditions the installation of a product using an impact mole is simple and straightforward. The…
ISTT
Impressed Signal Techniques
The methods grouped as impressed signal techniques all involve tracing the location/alignment of a buried utility by introducing a signal into the pipe or cable and then marking the strongest evidence of that signal on the ground surface in order to gauge its horizontal location. Examples falling into this…
ISTT
In-pipe Camera Observation
Direct observation of an active leak or observation of evidence of prior leakage using an in-pipe camera is the most common way to identify specific sources of I&I. An inherent difficulty with this approach is that inspections are best performed during periods of low flow but that, during such low flow periods, a…
ISTT
In-pipe GPR
In-pipe GPR is a pipe wall and ground penetrating radar system that is specifically adapted for use within a pipe. The system directs the signal outwards through the pipe wall and into the surrounding ground. Information about the pipe wall condition, external soil voids and other near-pipe ground conditions can often…
ISTT
Infiltration / Inflow (Gravity Pipes)
Infiltration/ Inflow (I/I) can be defined as the process by which storm water or ground water enters into the sanitary sewer system. Infiltration is considered the groundwater that enters the system through its contact with the ground. Inflow is considered stormwater flow that enters the system through illegal or…
ISTT
Infrared Scanning
Infrared scanning of the wall of a pipe or tunnel can show information about any changes in the wall condition or the condition of the ground immediately outside the pipe or tunnel. Such changes may include the presence of annular gaps, delaminations, exterior voids, presence of localized groundwater flow, etc. These…
ISTT
Inserted Liner
This category covers all the types of liners that are inserted into the existing pipe from an access point (rather than being created through an application process to the interior surface of the host pipe). These liners may be “loose-fit” (e.g. when slip-lining techniques are used for renovation) or…
ISTT
Insertion Process
The first CIPP liner installed in London in 1971 was pulled into position within the host pipe and then inflated and cured. However, within a few years, an inversion installation process had been developed in which the impregnated liner was contained within a plastic handling layer and was unfurled (inverted) within…
ISTT
Inspection Application
The choice of inspection methods is significantly affected by the purpose of the inspection and the type of facility in which the inspection will occur. The main areas of application considered here are: preliminary inspection, mainline pipe or tunnel inspection, lateral or small pipe inspection, and manhole or…
ISTT
Internal Survey Techniques
Internal survey techniques for tracing the vertical and horizontal alignment of buried pipes and tunnels can involve several different techniques: In person entry pipe and tunnels, conventional surveying techniques can be used to record the precise alignment CCTV platforms or similar can be fitted with…
ISTT