For the past four decades trenchless technology and its forerunners have found increasing acceptance across all the major underground pipe industries. Increasing calls for environmental protection, reduction of social impact of construction works, the effects of climate change (flooding etc) and increasing focus on the carbon footprint of construction works mean that the various benefits of trenchless methods are becoming increasingly sought after.
Environmental needs
Work carried out at Waterloo University in Canada has estimated the greenhouse gas (GHG) production for open-cut and trenchless methods. The results of the work have shown very significant savings in GHGs when using trenchless technology with over 90 per cent less GHG production is some circumstances. The Waterloo University work has also led to the development of a ‘Carbon Footprint Calculator’ which gives engineers the facility to estimate the GHG output of a project. The calculator can be found at: http://www.nastt-bc.org/carboncalculator/nastt00.php
Other environmental issues of relevance to trenchless technology include increasing public awareness of the effects of road works on their daily lives and businesses, and the recent floods with questions about land drainage and other storm water handling systems being ‘fit for purpose’. Trenchless systems are therefore finding significant favour amongst utility owners, the Environment and Highways Agencies (in the UK) and local government offices, where they are practical to apply.
In the UK the introduction of permit systems for in-road operations in some cities to try to ease congestion, the spectre of lane rentals (Clause 74) and the move to place what is expected to be over 200,000km of currently private drains and sewers into the hands of the main water companies in April 2011 is likely to have an effect on how trenchless technologies are viewed.
Jacked pipes
Whilst governments and associated bodies look at the environmental and political aspects and responsibilities of the utility and infrastructure industries, manufacturers and contractors have continued research and development to improve and expand the techniques available to them. This includes new equipment and the application of new and existing systems to practical problems faced every day across the industry.
Herrenknecht’s subsidiary Bohrtec has introduced a novel steering technology to extend the application range of guided auger boring. Instead of using conventional ground displacing pilot drilling technology which cannot be used in dense soil or rock, the new patented steering technology, called ‘Front Steer’, overcomes the usual application restrictions and enables work in very dense strata (Standard Penetration Test – SPT values >35) and in moderately strong rock (strengths up to 20Mpa). This is done using a guided-head auger-borer system that excavates the ground as it advances. The development does not lose the economic advantages of guided auger boring using pilot rods because the guided auger boring system with Front Steer retains the advantages of quick and easy set-up of the equipment on site and simple operation.
McLaughlin of the US has introduced the CBM 48 cradle earth-boring machine designed to help speed the installation of steel casing used in the cross-country pipelines. First used in the USA in the 1960s and ‘70s as a means to install longer sections of pipeline casing in a more time efficient manner, McLaughlin has reengineered this proven technique to include state-of-the-art safety and control features. The cradle boring method saves pipeline contractors time because it is not necessary to set up from a construction pit, which is often necessary with conventional auger boring. A trench the length of the casing is excavated and the cradle boring machine along with the casing are suspended in the trench using pipe-laying or side-boom equipment.
Akkerman, a specialist in microtunnellers, guided boring machines and pipe jacking systems has introduced the Pilot Tube Microtunnelling system (PTMT). The difference between standard pilot auger boring system and the new PTMT is that, subsequent to the installation of the guided pilot bore and an initial expansion of the bore diameter with a reaming head and auger chain, the final ream to the pipe diameter and installation of the jacking pipe is achieved using a powered microtunnel cutter head. The PTMT system is designed for use by contractors installing pipe in diameters of 500-1200mm o.d. It operates in a 3-pass process installing first the pilot tubes followed by the use of temporary casings and augers to increase the bore diameter and finally using the powered cutter head behind the temporary casings and reversing the auger flow toward the reception shaft. Subsequently the product pipe is jacked into the bore.
HDD developments
Various new horizontal directional drilling (HDD) rigs have been introduced recently.
Vermeer has expanded its line of Navigator horizontal directional drills with the three maxi-size units: the D500x500, the D750x900 and the D1000x900, all for large diameter pipes. Based on Horizontal Rig & Equipment (HRE) designs, acquired in 2008 by Vermeer, the three drills feature respective pullback forces of 500,000lb, (225,000kg), 750,000lb (337,500kg) and 1000,000lb (450,000kg).
Vermeer has also introduced the D9x13 Series II Navigator horizontal directional drill designed for confined jobsites and areas where surface disturbance to turf, such as residential and commercial lawns, is a concern. The newly introduced compact model will be especially useful for fibre-to-the-home and other utility installations. The new D9x13 is designed to accommodate over 90m of drill rod for longer bores and has a 2-speed rotation gearbox to enhance controllability, allowing the operator to increase backreaming speed when conditions allow.
For very accurate boring requirements, the Axis guided boring system from Vermeer is a pit-launched, laser-guided tool to install 10-14in. (254-356mm) diameter pipe. The system can achieve pinpoint accuracy and its versatile design allows for multiple applications in the installation of new water and sewer pipelines.
Ditch Witch also announced the release of what is claimed to be its most powerful directional drill to date, the JT100 Mach 1. Equipped with a 200kW engine, the JT100 is designed for rotation, thrust, and drilling fluid flow to operate simultaneously at full power, which leads to faster job completion. With 445kN 100,000lbf (445kN) of pullback and 12,000 ftlbf (16,270Nm) of torque, the JT100 is built for both long-range bores, such as river crossings, and installation of large diameter pipe. An onboard crane is used to load and unload pipe boxes, anchor the unit, and handle downhole tools. An optional feature is an onboard anchor system, exclusive to Ditch Witch, which stabilises the machine on virtually any terrain.
As for support equipment for HDD the DCI DigiTrak F2 delivers the most popular features of the Eclipse locator with enhanced sensitivity and greater ease of operation. The DigiTrak F2 incorporates DCI’s patented 3D antenna and ‘target-in-the-box’ locating with a new depth screen display for high accuracy and clarity. A 2-dimensional bird’s eye perspective is viewed on the same screen as the depth view. This means for the first time with an HDD locating device it is possible to actually view the drill head location in 3 dimensions in real-time. The data display screen is streamlined to provide transmitter roll, pitch, signal strength and temperature in a single column view.
Pipe replacement
Pipe replacement techniques have become increasingly popular over the past decade, but one of the questions asked by many end users has been ‘How will the broken shards inter-react with the new pipe as it gets pulled in?’ In some cases shards have caused the new pipe to be damaged during installation. This has led to deliberate over-engineering of the new pipe to make allowances for damage, or the use of over-sized bore expanders to maximise the void into which the new pipe is pulled.
Perforator of Germany, along with its UK subsidiary of Sheffield, has introduced bursting rigs designed to overcome this problem, including the RBZ60 with a pullback capacity.
Working in exactly the same way as traditional hydraulic rod-based pipe bursting systems, the major difference between the new rigs and the old style is that, using an independent grout injection system, a cement grout mix is pumped through a feed line running inside the new replacement pipe. The grout is extruded under pressure via ports in the expansion head that are positioned to ensure that the grout is uniformly placed around the new pipe as it is pulled in. The grout combines with the old pipe shards and the mix is pushed into the surrounding ground, cementing the shards into place so avoiding pipe/shard interaction and eliminating the need for over-engineering.
Renovation developments
Pipe renovation has been around for over 30 years, but some of the latest developments have been designed to overcome difficulties experienced with some of the more traditional lining systems.
For example, where it is necessary to introduce a very thick walled liner to maintain or enhance the structural capacity of a pipeline, existing materials do not always have the capacity to meet these requirements or the installed liner will reduce the overall capacity of the pipeline for long-term operation.
Insituform Technologies has recently developed a system designed to eliminate this problem. The iPlus composite liner comprises a fibre-reinforced liner material that is designed for rehabilitating gravity pipes from of 610-2,100mm diameter.
Reinforcing fibres are integrated into the liner wall to form a laminated sandwich structure with improved physical properties. The improved flexural strength makes iPlus liner suitable for non-circular cross-sections that contain straight sides (eg. egg shapes or flat-bottom arch pipes) as well as those likely to be subject to higher than usual external loadings (eg. high long-term traffic flows).
The iPlus enables increased flow capacity relative to the host pipe compared with more conventional rehabilitation product combinations. The product, due to the reinforcement with carbon and/or glass fibres, provides a structural solution that is approximately 50 per cent of the thickness of traditional pipe liners to maximize pipeline capacity after lining. The new liner’s reinforcement fibres are also resistant to the corrosive materials and conditions found in sewers.
Insituform also claims that iPlus uses less resin than traditional products, less energy to cure the product, less fuel in factory-to-site transport and can be installed in less time than conventional cast-in-place pipe (CIPP), so saving energy and reducing emissions across the lining process. iPlus composite liners have a polypropylene coating on the inner surface increasing the pipe’s smoothness, reducing surface friction and providing an additional corrosion barrier.
Independent testing of iPlus carried out at Coventry University, UK, established the E-Modulus of the cured liner to be over 5000Pa. One of the three samples tested showed an E-Modulus of over three times the industry recommended level of 2200Pa for this type of liner.
There has also been progress over recent years in lateral connection seals. For example Trelleborg announced that both its 45° and 90° lateral seal product passed WRc’s long-term infiltration test, in accordance with the infiltration limits set under the Sewers for Adoption 6th Edition (based on the BS EN 1610 standard) for this type of installation. The WRc test requires installation of the lateral seals to be made into four independent test rigs where clayware pipes are installed, without damage, in a manner similar to those used on real-life installations in the ground. This includes three months exposure to an external hydrostatic water pressure head of up to 5m in a cyclic pressure regime designed to imitate a working cycle likely to be encountered by the product in service. The leak tightness of the lateral seals is regularly monitored over the test period.
Brawoliner has introduced Brawoliner satellite packing pieces and collars. These units are designed to meet the requirements where renovating faulty pipe unions. Brawoliner supplies a tight-fit solution for German-standard DN 100-DN 225 main pipes and DN 70-DN 225 feeders. The new satellite packing pieces and flexible collars allow fast, easy, affordable and reliable renovation of even complex fall pipes.
The renovation of building down-pipes is also becoming a growth area for the use of trenchless systems normally applied horizontally. With increasing numbers of buildings having deteriorated down pipes that have been built either inside the structure or which are otherwise difficult to access, the need to renovate these pipes without disruption to the building, its occupiers or the system is becoming more widespread. The technique has also become available for the lining of waste chutes within high-rise buildings for similar reasons.
Ancillary developments
Across the trenchless technology market it has long been a wish to develop a system of ongoing pipe maintenance that minimises the need for internal intervention, particularly where this would require confined space, man entry. One requirement has been how to keep operational sewers and drains clean.
One system that has been developed to meet this need has been the Flusher, introduced by UK-based Infotec, which is more widely known for its expertise in the field of utility and buried systems tracing and mapping.
Flusher is an innovative drain and sewer cleaning system that utilises the potential energy within the sewer to clean itself and the surrounding catchment area. The system can be demounted and moved to different locations, enabling it to be used as an effective maintenance tool and an environmentally-friendly solution.
It is a gate device that, once installed, starts initially in a closed position, causing effluent flows to accumulate on the upstream side of the gate. When the flow reaches a set level, the gate opens fully, releasing the contained effluent to surge through the sewer in high volume and at a high flow rate, so scouring fats, silt, or other built up material from the sewer walls and out of the invert. The process is continually repeated allowing any materials or deposits left behind by one cleaning action to be removed by the next. Because the flow level varies, deposit build ups are dramatically reduced throughout the pipeline. A range of pre-fabricated Flusher systems is available for pipes of 100-600mm nominal diameter.
Remote sensing units and techniques are increasingly being utilised to minimize disruption during surveys or buried services. One of the most recent additions to the field is the PipeHawk e-Spade ground probing radar system. Using ultrawide band co-polar antennas within an impact-resistant moulded body, the e-Spade radar signal feeds information to the on-board, high-spec processing computer. This is controlled via icon-driven software for ease of use with built-in USB ports for quick and easy data transfer. The most up to date communications technology can also be used in conjunction with such systems, interfacing site with office and client as required.
The PipeHawk e-Spade is available in three models including; the Standard e-Spade designed for low use requirements, e-Spade+ that has the addition of the latest version of PipeHawk’s tried and tested mapping software, and the e-Spadepro at the top end of the range for high accuracy, professional utility surveys with a global positioning system (GPS) facility.
So it can be seen that trenchless technologies not only continue to develop but are also finding new areas of application.
Bohrtec’s new Front Steer auger boring system The CBM 48 cradle earth boring system from McLaughlin The D1000x900 Navigator is Vermeer’s largest HDD rig The powerful JT100 Mach 1 HDD rig from Ditch Witch The DCI DigiTrak F2 is a popular support for HDD rigs Perforator’s RBZ160 pipe-burst rig, is the defunt older brother to the RBZ60 Section through Insituform’s new iPlus composite liner for pipe renovation The Pipehawk e-Spade ground probe radar is a recent addition to the field Diagram showing a Flusher demountable unit in position. Developed by Infotec, the Flusher automatically cleans a sewer of detritus
