ISTT

Organisation for Trenchless Technologists

The International Society for Trenchless Technology (ISTT) exists to promote the benefits of trenchless technology, and to facilitate the development and implementation of trenchless technology, worldwide. There are now more than twenty such affiliated societies in five continents, and each is entitled to nominate a director on the ISTT board. For efficient day-to-day running, an executive sub-- committee is empowered to act for the full Board.

ORGANISATION FOR TRENCHLESS TECHNOLOGISTS

Since its formation in the United Kingdom in September 1986, as an international ``umbrella`` organisation for trenchless technologists worldwide, it has since encouraged the formation of national and regional organisations to serve these technologists wherever they live, by working locally using national languages and business practices. The ISTT board manages the affairs of the society and determines its broad strategic and policy direction. It meets once a year at the international no dig event. The chairman of the board is elected for a two or three year term. The ISTT also has charitable (not for profit) status in England and a separate Board of 12 Guarantors are the trustees of this charitable status, legally liable for ensuring the Society meets its charitable objectives and complies with UK law. The Secretariat, or administrative arm of the Society is managed by a part time Executive Secretary (the principal executive officer of the Society), who is supported by a Membership Secretary and part time Technical Secretary. International working groups are established from time to time by the Board for particular investigations, studies, activities and joint activities with other related specialist organisations. The Chairman of each Working Group is responsible for the activities of the Group, and reports to the Board at the International no dig events. The ISTT was established with the following aims and objectives:

Aims

• to advance the science, practice and application of trenchless technology for the public benefit worldwide
• in ``science``, this covers training, education, publications and research
• in ``practice`` this covers all the techniques, procedures and materials, including related activities such as condition monitoring, contracting , insurance and finance
• in ``application`` this covers all manner of underground work on utility networks and related civil engineering activities

Objectives

• advance the science and practice of trenchless technology for the public benefit
• promote education, training, study and research in the science and practice of trenchless technology

The society currently consists of national societies and their memberships. The ISTT registers members in London who reside in countries where there is no national society.

Societies

Organizations are subject to some simple requirements in order to be affiliated to the ISTT. These affiliated societies share the objectives of the society.

National Societies

• Australasian Society for Trenchless Technology (ASTT)
• Austrian Society for Trenchless technology (AATT)
• Brazil Society for Trenchless Technology (ABRATT)
• China Hong Kong Society for Trenchless Technology (CHKSTT)
• China Society for Trenchless Technology (CHSTT)
• China Taipei Society for Trenchless Technology (CTSST)
• Czech Society for Trenchless Technology (CzSTT)
• Finland Society for Trenchless Technology (FiSTT)
• French Society for Trenchless Technology (FSTT)
• German Society for Trenchless Technology (GSTT)
• Hungarian Society for Trenchless Technology (HSTT)
• Iberian Society for Trenchless Technology (IbSTT)
• Indian Society for Trenchless Technology (ISTT)
• Italian Association for Trenchless Technology (IATT)
• Japan Society for Trenchless Technology (JSTT)
• Netherlands Society for Trenchless Technology (NSTT)
• North American Society for Trenchless Technology (NASTT)
• Polish Foundation for Trenchless Technology (PFTT)
• Russian Society For trenchless Technology (RSTT)
• Scandinavian Society for Trenchless Technology (SSTT)
• Slovak Society for Trenchless Technology (SVSTT)
• Southern Africa Society for Trenchless Technology (SASTT)
• Swiss Society for Trenchless Technology (CHSTT)
• Ukraine Society for Trenchless Technology (USTT)
• United Kingdom Society for Trenchless Technology (UKSTT)

Awards

An individual award is made, when appropriate, to persons who are judged to have made an outstanding and exceptional individual contribution to trenchless technology. The award relates specifically to individual contributions judged to meet ``outstanding`` and ``exceptional`` criteria. The award comprises a silver gilt medal inscribed around the rim with the recipient's name and an appropriate certificate. The medal is presented by the ISTT chairman at a suitable ceremony, usually the opening ceremony of an international no-dig.

The award for the most notable advance is divided into 4 categories. They are project, product, academic and student. no dig events are important for networking, marketing and general promotion of trenchless technology.

Publications and Research: Practical Trenchless Techniques

The ISTT supports basic research on matters that form the basis on which practical trenchless techniques depend. Matters can range from soil mechanics, strength of materials, fluids, measuring techniques, and computing to risk analysis, economics and law.

Journal

The lifeblood of research is the publication and exchange of information. The ISTT publishes an official research journal for the society, ``Trenchless Technology Research``, as a supplement to ``Tunnelling and Underground Space Technology`` which it publishes in co-operation with the International Tunnelling Association. The combined journals have articles of equal interest to both tunneling experts and trenchless technologist. The peer review and publication of research material is a time consuming and expensive process, and hence the journal is only supplied to subscribers. ISTT members get a discount.

Forums and Meetings

An informal meeting is supported by the ISTT each year of academics and researchers, the Trenchless Technology Colloquium. This is held each year on a university campus where the delegates decide their agenda and exchange ideas on the direction for research in which trenchless technology should be encouraged and taught at first degree, masters and doctorate levels.

Monthly Magazine on the Trenchless Industry

Trenchless technology magazine began in 1992 as a bimonthly publication and quickly moved to monthly in 1994. The magazines editorial calendar provides cutting-edge information on the hottest areas of the trenchless industry. Trenchless technology refers to the numerous underground construction methods that eliminate or minimize surface disruption. The trenchless technology magazine helps in the promotion and development of the trenchless industry.

Newsletter

Anyone who registers will receive occasional newsletters which provide updates and information about the trenchless pipe installation business.

Trenchless Techniques

TRENCHLESS PIPE INSTALLATION

The method of forming a bore, usually from a drive pit, using a rotating cutting head is called the Auger boring method. Soil is removed back to the drive pit by helically wound auger flights rotating in a steel casing. The equipment may have limited steering capability. Guided Auger boring is the term applied to Auger boring systems which are similar to microtunneling, but with the guidance mechanism actuator sited in the drive shaft (e.g. a hydraulic wrench which turns a steel casing with an asymmetric face at the cutting head). The term may also be applied to those Auger boring systems with rudimentary articulation of the casing near the cutting head activated by the rods from the drive pit. The advantages of this tunneling system are that it causes little or no disruption to soil surface and no disruption to traffic. Its limitations include a very rudimentary steering system, thorough site investigations required and large boulders or very soft ground can cause problems.

HORIZONTAL DIRECTIONAL DRILLING METHOD (HDD)

The HDD method contains impact support  and is called the Grundodrill technique. It enables trenchless installations up to 500 m length. The spectrum of application includes all pipe construction measures within the bounds of gas, district heating and drinking water supply, the installation of pressure lines for sewers as well as cable protection pipes for television or telephone cables, traffic routing systems, emergency call boxes or low, medium, high voltage and optical fibre cables. The HDD method is extremely protective towards the environment and causes no ecological damage at all. There are several reasons for the application of the directional technique in central town areas. They mainly concern the construction costs, construction periods, permission procedures, soil displacement, surface restoration and the traffic, compared to open trenching methods. The normal course taken by the drilling operation includes: planning, preliminary survey, selecting the drilling units and drilling tools, pilot bore and detection, backreaming(s) or upsizing bore(s) and pulling in the pipe. To overcome mechanical soil resistance high thrust and tension forces are required. The application of Bentonite might relieve the pilot bore and the pipe traction and provide the ability to steer in difficult soil qualities up to soil grade 5 or even 6. The HDD method is advantageous because surfaces worth conserving are neither broken up nor damaged, restoration and repair are not required,  which leads to high  economical advantages, low social costs because detours are avoided, short equipping as well as drilling and construction times, economic for river crossings, supported by the dynamic impact of the striking mechanism, the propulsion and ability to steer are improved in soil qualities of up to grade 5 and 6, it is an acknowledged procedure and pulling force measurement and position determination are possible.

PIPE JACKING TECHNIQUE

Pipe jacking, generally referred to in the smaller diameters as microtunneling, 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 and at the same time, excavation takes place within the shield. The method provides a flexible, structural, watertight, finished pipeline as the tunnel is excavated. Practical engineering considerations and economics may impose restrictions. A number of excavation systems are available including manual, mechanical and remote control. Pipes in the range of 150mm to 3000mm can be installed. Excavation methods are either manual or machine excavation. To install a pipeline thrust and reception pits are constructed, usually at manhole positions. The dimension and construction of a thrust pit may vary according to the specific requirements. Mechanised excavation may require larger pits than hand excavated drives, although pipe jacking can be carried out from small shafts to meet special site circumstances.

A thrust wall is constructed to provide a reaction against the jack. High-pressure jacks provide the substantial forces required for jacking concrete pipes.

SOIL DISPLACEMENT METHOD

The soil displacement method is a method for underground pipe installation. A displacement hammer, driven by pneumatics, creates a cavity underground, ready for pulling in short or long pipes made of plastic and metal, preferably without socket ends, up to DN 200, but also any type of cable in drill lengths up to 40 m (depending on the soil quality). This allows trenchless traffic route crossings, private service line installations, the preparation of anchoring, bypassing obstacles and supporting further measures. This is a better method to be used in rocky soils because the complete impact capacity can first be concentrated on the multi-cutter cone.

DRY BORING METHOD

This is a combination of the soil displacement method with steered displacement hammer. Its advantages include: surfaces worth conserving are neither broken up nor damaged, economic advantages such as low social costs because detours, half-sided barriers and set up of signal facilities are   avoided, it is suitable for longer private connections and traffic route crossings, no residential problems when installing private connections, short set up and propulsion time required, small pits used for short and long pipes without socket ends to 200 mm displaceable pipe diameter.

MICROTUNNELING

Microtunneling is a process that uses a remotely controlled Microtunnel Boring Machine (MTBM) combined with the pipe jacking technique to directly install product pipelines underground in a single pass. This process avoids the need to have long stretches of open trench for pipe laying, which causes extreme disruption to the community. Typical microtunnel equipment spread consists of an MTBM matched to the expected subsurface conditions and the pipe diameter to be installed, a hydraulic jacking system to pipejack the pipeline, a closed loop slurry system to remove the excavated tunnel spoil, a slurry cleaning system to remove the spoil from the slurry water, a lubrication system to lubricate the exterior of the pipeline during installation, a guidance system to provide installation accuracy, an electrical supply and distribution system to power all of the above equipment.

Trenchless Pipe Rehabilitation

RAMMING METHOD

Dynamic ramming method uses unsteered ramming with pipe propulsion along with the use of a pneumatic pipe ramming machine. With these, open steel pipes can be laid beneath railway tracks, highways and rivers, either as protection or product pipes, with diameters up to 2000 mm for lengths of up to 80 m in the soil without using pressing abutments. The ram is driven by compressed air and has cotter segments to establish a connection between the machine and the pipe. Due to the two gaps in the soil removal cone or adapters, part of the tension of the spoil carried along, is released. The application of cotter segments prevents the pipes from flaring up and enables high quality butt welds of the single pipe lengths. The casing friction of the inner or outer pipe is reduced by bentonite cutting shoes that simplify pipe propulsion by lubricating the pipe. The minimal displacement volume in the area of the cutting shoe eliminates the risk of road surface heave, and means that work can commence even from shallow pit depths. Advantages of the method include surfaces worth conserving are not broken, restoration is not required, low social costs, acknowledged procedure, short set-up times, short pipe laying times, no pressing abutment, no conveyor spiral, no flooding when working on river crossings, minimal covering, no elaborate pits, simple operation technique and adaptation to all pipe diameters with a special ram cone.

TRENCHLESS PARALLEL NO-DIG TECHNIQUE

The trenchless parallel no dig technique is a further developed and refined version of the water flush drilling method that has been developed by Stadtwerke Schwerte GmbH. It solves the problem of space availability for all sorts of utility lines by considerably reducing space both above and below ground, thus making it possible to lay a bundle of pipes in a one step operation without twisting and trenches in precisely defined distances.

TRENCHLESS PIPE REHABILITATION

Trenchless pipe rehabilitation refers to the method of trenchless pipe replacement through the renewal method which includes:

DYNAMIC PIPE BURSTING

In the method of dynamic pipe bursting, the bursting machine is pulled by a winch through the old pipe meant to be renewed. During this procedure, the old pipe is destroyed by dynamic impact energy and the fractured particles are pushed into the surrounding soil, while the new line, in the same width or one size larger, is pulled in at the same time.

PIPE EATING BASED ON MICROTUNELING

Pipe eating is a replacement technique based on microtunneling, where the defective pipe is excavated together with the surrounding ground, as it would be for a new installation. The pipe eating shield is pushed forward along the route of the existing pipeline using hydraulic jacks, located in the drive shaft. The replacement pipes are connected to the back of the tunneling shield. On completion of the drive length the pipe eating shield is recovered at the reception shaft, leaving a new pipeline in place of the defective pipe.

PIPE EXTRACTION METHOD WITH GRUNDOBURST

Pipe extraction method with grundoburst is the method wherein damaged gas and water lines, can be easily replaced by new pipes in the same bore path.

PIPE SPLITTING METHOD FOR TRENCHLESS PIPE REPLACEMENT

Pipe splitting method solves the problem of lead pipes being replaced by plastic pipes to supply potable water. This method was developed by the Water Supply Company of Berlin, in order to carry out trenchless lead pipe replacement within the field of house connections.

STATIC PIPE BURSTING METHOD

Static pipe bursting method with the patented Grundoburst is used to replace old pipes, especially in sensitive soils within the vicinity of other external lines. It is often used for the renewal of potable water lines where stems are pushed through the old line first. The old pipe line is actually cut open by the roller blade immediately followed by the expansion head. Advantages of this method include: path of the old pipe can be used,  bursts grey cast iron, asbestos-cement, stoneware, concrete and plastic, pipe bursting can also cut ductile grey cast iron and steel new pipe with new longevity improvement of the hydraulic capacity, because the new pipe to be installed is 1 or 2 sizes larger, no reduction of the cross section, applicable for all types of damage, good bedding conditions, short equipping time and simple operation technique, high daily capacity of up to 150 m.

Trenchless Pipe Renovation

The renovation technique of trenchless pipe replacement includes: cement mortar lining, cipp lining, close fit lining, deformed pipe lining, epoxy spray lining, sliplining, spirally wound lining, tight-in-pipe short pipe relining, swagelining and rerounding.

CEMENT MORTAR LINING

Cement mortar lining is the application of a cement mortar (typically about 4mm thick) to the inside of pipelines to protect against corrosion.

CIPP LINING

Cipp lining (lining with cured in place pipes) is a renovation technique consisting of the insertion of a flexible tube of fibrous matrix, filled by a thermosetting resin, into a water main to produces a structural pipe when cured.

CLOSE FIT LINING

Close fit lining is a technique for pipeline renovation, in which the cross section of the liner is temporarily deformed before insertion into the carrier pipe. The different types of close fit lining systems are: deformed pipe, die drawing or swagelining and rolldown.

DEFORMED PIPE

Deformed pipe is the alternative to reducing the diameter of the liner to deform it or fold it to enable it to be inserted into the carrier pipe.

DIE DRAWING OR SWAGELINING

Die drawing or swagelining, involves the reduction of the diameter of the liner by heating and pulling it through a tapered steel reducing die which squeezes it until its diameter has been reduced.

ROLLDOWN PROCESS

Rolldown process is where the diameter of the liner is semi-permanently reduced before it is inserted into the carrier pipeline.

DEFORMED PIPE LINING

Deformed pipe lining is used for the installation of the liner into the host, and includes:
compact pipe, subline system, subcoil system and thermopipe.

COMPACT PIPE

In this system PE pipe is factory extruded in a ``C`` shape and coiled onto a drum and pressurized with steam, which rounds the liner, to form a close fit within the host pipe.
 
SUBLINE

The subline system involves the folding of thin walled polyethylene (PE) into a U shape to create a clearance for the installation of the PE pipe into the host pipe, which is then pressurized to snap the bands allowing the liner to revert back to its original shape.

SUBCOIL

In the subcoil system PE pipe is factory folded into a ``U`` shape, held by a continuous sleeve and then coiled onto a drum. The folding creates a reduction in diameter, giving clearance for installation of the liner.

THERMOPIPE

Thermopipe is a circular woven, high tensile polyester reinforced, polyethylene lining system which is semi-rigid when cool, but once pulled into the pipe, inflated and heated, it becomes flexible and expands, providing structural lining.

EPOXY SPRAY LINING

Epoxy spray lining is a method of lining pipes with a thin lining of resin (typically 1mm thick), which is sprayed onto the surface of a cleaned main and isolate the host pipe from the conveyed medium.

SLIPLINING

Sliplining is the technique by which a continuous or discreet pipe is inserted within existing pipes. 

SPIRALLY WOUND LINING

Spirally wound lining consists of a plastic strip spirally or helically wound to form a continuous lining and does not require special road openings to accommodate variations in cross section and large radius bends. 

TIGHT-IN-PIPE SHORT PIPE RELINING

Tight-In-Pipe short pipe relining (TIP-method) allows short sewage pipes to be installed trenchlessly from manhole to manhole, reducing the  necessity for filling the annulus.

SWAGE LINING

In the swagelining and die drawing method, close fit thermoplastic pipe lining systems are achieved by stretching a liner pipe by pulling it through one or more dies, to produce a temporary reduction in its diameter. It includes:

ROLLDOWN

Rolldown is the technique where close fit thermoplastic pipe lining systems are achieved by pushing a liner pipe by pulling it through one or more sets of rollers, to produce a temporary reduction in its diameter.

REROUNDING

Rerounding, carried out prior to renovation of a pipeline, consists of the insertion of expansion devices or mechanical props to restore a deformed pipeline to its original shape.

Trenchless Pipe Repair Method and Plow Systems

The repair method of trenchless pipe replacement includes air sourcing, chemical stabilization, flushing, jetting, joint sealing and testing, patch repair systems, pigging, pointing, pressure scraping, resin injection and robotic systems.

AIR SOURCING

Air sourcing is a cleaning method that uses compressed air, blown into a flowing stream of water to remove loose pipe deposits and small animals and improve water quality.

CHEMICAL STABILISATION

Chemical stabilization is the renovation of a pipeline and ancillary features by sealing, between two access points by the chemical reaction of added compounds to the surrounding ground.

FLUSHING

Flushing is a method for cleaning water mains by allowing a high flow of water through a pipeline to improve water quality.

JETTING

Jetting is a method for cleaning water mains using pressurised water directed onto the inside of the pipeline to remove deposits including encrustation, corrosion deposits and damaged or faulty linings.

JOINT SEALING AND TESTING

This method is used to test and seal defective pipe joints with a grout using a packer which combines the functions of leak testing and grout injection.

PATCH REPAIR SYSTEMS

This is a localised pipe repair system that involves positioning a short sleeve of resin-impregnated material within the host pipe and curing it.

PIGGING

Pigging is an aggressive cleaning technique which involves passing abrasive pigs through a pipeline along with a jet of water and ensures maximum removal of encrustation.

POINTING

Pointing and chemical grouting of joints is a repair method to prevent infiltration and exfiltration through joints or deteriorated mortar in brick sewers that are structurally intact but suffer infiltration.

PRESSURE SCRAPING

Pressure scraping is a technique which uses a cylindrical scraper unit, driven through the pipeline to remove deposits and encrustation.

RESIN INJECTION

Resin Injection is the localised repair of pipes by injection of a resin formulation such as epoxy resin or mortar into defects and the subsequent curing to prevent leakage and further deterioration.

ROBOTIC SYSTEMS

Robotic systems for gravity pipelines comprise of grinding and filler robots that remove encrustation and intrusions and mill out cracks to provide a good surface and key for the repair materials.

PIPE AND CABLE PLOW SYSTEMS

Pipe and cable plow systems include: pipe and cable plow and the rocket plow.

PLOWING TECHNIQUE  

The plowing technique is especially suitable for sparsely populated rural areas where long pipelines with few connections are required. Up to now only pressure lines are installed with this technique. Due to the plow design and its universally adjustable extensions, even small, flat waters can be crossed and pipes can easily be installed in embankments. Applying the plowing technique to install pipes below ground water level has proved to be very economic and environmentally friendly. The terrain should not be fortified and should be free of larger obstacles. Prior to the installation the exact position of crossing lines and the prevailing soil conditions have to be investigated.

PIPE AND CABLE PLOW

An all terrain traction unit (Unimog or tracked vehicle) pulls the plow by aid of a cable winch. Bumpy terrains are levelled by universally adjustable extensions and hydraulically adjustable rubber tyres. At the starting point of the bore path the plow lamella is placed in the starting pit at a level with the installation depth. Being pulled by the rope, the plow lamella displaces the soil in the pipeline zone, settling the ditch bottom with its own high weight. That way a hollow space for installing the pipe is created. By means of an automatic sanding cart attached to the plow, the hollow space can be filled with sand. Then the pipe is installed on the bottom of the ditch at the desired depth free of any mechanical stress. The pipe and cable plow installs PE and PE-X pipes up to OD 255 mm.

ROCKET PLOW

When using the rocket plow, the installation box is exchanged for a displacement and extending piece. The rocket plow installs PE and PE-X pipes up to OD 335 and ductile cast iron pipes up to ND 250. The pipe is attached directly to the displacement and extending piece and pulled into the hollow space the piece has created. Additional protection pipes, cables and trace bands can be pulled in simultaneously. A bentonite mix can be applied to fill the annulus around the pipe and to minimize the friction. Monitoring the pulling forces affecting the pipe string is possible as well.