Within the civil engineering world, finding safer and quicker methods to finish tasks with minimal influence on the surroundings and public is the main target for many house owners, designers and contractors. I consider horizontal directional drilling (HDD) is likely one of the most fascinating technologies that lets us install pipelines, sewer, water mains, power and telecom where typical open-cut methods aren’t possible.
Most of you understand about HDD, but for those of us who’re new to it, here is the fast introduction to HDD earlier than the Q&A with the specialists:
HDD technique is about making a horizontal borehole from one location to a different. The process sometimes begins with boring a small pilot gap alongside the desired centerline of a proposed profile underneath the crossing obstacle (e.g., a freeway) with a steady string of metal drill rod. The position of the drill head could be precisely managed with units and sensors that monitor and monitor the drill head. By means of small adjustments made by the operator, the drill head can go round timber, beneath foundations, buried utilities, lakes, or other obstructions.
When the bore head and rod emerge on the other aspect of the crossing, often a special cutter, referred to as a again reamer, is hooked up and pulled again by means of the pilot hole. The reamer bores out the pilot gap so that the pipe may be pulled by means of. The pipe is often pulled via from the aspect of the crossing opposite the drill rig.
The reaming operation often consists of utilizing an applicable device to open the pilot hole to a barely bigger diameter than the service pipe. Several reaming passes could also be needed for large-diameter pipes which require giant boreholes that can’t be created in a single cross. Often, a “drilling mud” resembling fluid bentonite clay is injected into the bore whereas chopping and reaming to stabilize the opening and take away soil cuttings.
Erez Allouche, Ph.D., P.Eng., Follow Know-how Leader,
Carrie Murray, M.Eng., P.Eng., Principal Geotechnical Engineer, Stantec.
Bertus Vos, MBA, P.Eng., Principal Engineer, Bluefox Engineering
Robert Dalgleish, HDD Product Help Specialist, Vermeer
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1. Where do you see the HDD market heading within the next 5 to 10 years (new markets, present gaps in HDD capabilities)?
Vos: We see the HDD business continuing to develop and increase. We anticipate a big improve in urban group software where stakeholders have to cross obstacles and wish to scale back the impacts of development on their communities. We are seeing the chance to make use of the know-how in several new industries that have been perhaps a bit hesitant a couple of years in the past. We have now found that owner and designer schooling still remains a “hole,” and informing these stakeholders of the capabilities, dangers and software of the know-how will play a crucial position over the subsequent few years with a view to continue to broaden into new markets.
Allouche and Murray: Continuous enhancements associated to wireless know-how shall be integrated into HDD tasks, reminiscent of directional steerage and annular strain monitoring. Improvement of hybrid methods will continue to beat the challenges associated to HDD, such as the methods which mix some great benefits of HDD and microtunneling to create distinctive trenchless options.
Current development in reamer know-how allows pushing reamer diameter past the 60-in. barrier. Other enhancements embrace improvements in drilling fluid chemistry, to raised handle the loss of circulation and stability issues in coarse granular formations, and incorporation of ground improvement methods into HDD designs. These further prolong the power of the HDD business to deal with complicated subsurface circumstances.
Dalgleish: Rock bores are becoming extra widespread and gear has advanced to satisfy the problem, twin rod or rod-in-rod drill rigs use the internal rod to show the rock bit on a bent sub rock head. Air hammers and hammer reamers cycle at excessive frequency – excessive frequency means smaller cuttings which might be easily transported out of the borehole. To offer air to the hammer’s compressor, manufacturers have models that present greater CFM and PSI in a small footprint which might be additionally extra gasoline efficient and function at lower decibels.
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2. What are probably the most priceless “lessons discovered” with regard to the design and development of HDD tasks? What are some areas of future improvements/enhancements?
Dalgleish: Bore design is crucial and that’s why software program purposes have been developed to take the consumer by means of the design and planning strategy of an HDD bore in a sequential method. Other purposes which are web-based have been developed for contractors to seize and handle digital jobsite documentation in one place to simply share with others. With mapping know-how, you possibly can mark utilities, plan bores in real-time and export studies to raised collaborate and save time earlier than, during and after a job.
Allouche and Murray:Bore instability and lack of drilling fluids continue to be main considerations with HDD owing to the presence of an uncased open gap in the course of the drilling, reaming and pull-in operations in gravelly materials. The geotechnical investigation and delineation of the subsurface together with gravels is a mandatory input into the design process and development planning and execution of the HDD. Ought to the need to construct by way of gravelly soils be required, assessing the feasibility of the trenchless know-how and mitigation strategies obtainable to handle the danger impacts is important to attenuate or forestall value overruns, schedule delays, environmental and social impacts.
Given the complexities with HDD development in gravelly soils, it is very important accurately set up the stratigraphic profile and characteristics of the gravelly soil so that applicable design measures could be included into the drill path design in addition to the event of mitigation strategies during development that may embrace site-specific drilling fluid administration and drilling practices.
Conductor casing set up enhancements utilizing different trenchless strategies/hybrids (e.g., pipe ramming, auger, pipe thruster) supply an alternative choice to typical hammering which may accommodate larger lengths and diameters and improve general installation effectivity. In current yr vital progress was made in the improvement of Lack of Circulation (LOC) supplies used to stabilized high permeable formations and the incorporation of ground enchancment methods into HDD designs.
Vos: Correct planning, engagement and communication are a few of the essential gadgets to the successful design and execution of an HDD. For future undertaking enhancements, we encourage undertaking house owners to interact the HDD design and development groups as early on as a challenge permits. HDDs are sometimes attributed to a number of the highest value and danger exposure on a undertaking and the power to develop a design and execution technique together (combining stakeholders from the proprietor, engineer and contractor) has the potential to mitigate dangers and exploit constructive alternatives. Lack of communication with all stakeholders is a root reason for most of the lessons discovered we encounter on tasks.
3. What are your recommendations on “mud” engineering and chemistry of drilling fluid?
Vos: Drilling fluid must be engineered for each HDD software, based mostly on the geology, surroundings, sort of kit selected and the execution technique of the contractor. The chemistry of the drilling fluid needs to be engineered underneath the gear’s mechanical circumstances and be developed to perform inside the geological stratigraphy anticipated and the environmental sensitivity of the situation. Water, drilling fluid and disposal transportation can attribute to vital value and logistical requirements for large-scale HDD tasks. We search opportunities for enhancements in drilling fluid engineering and dirt system capabilities that may permit for fluid re-use, along with decreased disposal volumes and water necessities.
Allouche and Murray: Drilling fluid is the life-blood of the HDD course of and the event of applicable and site-specific drilling fluid composition and management is obligatory on all maxi HDD tasks. This apply requires careful consideration of the geotechnical properties and traits of the subsurface soil and groundwater circumstances relative to the HDD execution plan. During HDD development, the drilling fluid properties ought to be frequently examined by an HDD skilled drilling fluid specialist (for funnel viscosity, unit weight, sand content material, gel power and shear stress measurements using a viscometer to find out obvious viscosity, plastic viscosity and yield level) to allow for on-site optimization of cuttings removing, filter cake improvement and efficient fluid recycling.
Drilling fluid and solids disposal prices continue to escalate depending upon regulatory necessities and the way the spoils are disposed. The drilling fluid administration plan must accurately estimate the quantity and costs for disposal to be environmentally and economically feasible. Utilization of solidification methods allows the drilling fluid to be recycled and the solids to be disposed by dump vans as an alternative of vac vans and should provide a larger range of disposal choices (regular landfill or floor cover). The event of a complete mud administration plan is a key component in any technique aiming at mitigating schedule delays and finances overrun, notably on giant pipeline crossings in environmentally delicate areas.
Dalgleish: Fluids “mud” can and sometimes make or break with regards to the success of an HDD challenge and very often the fluids are usually not given enough focus or consideration. Spending dollars on fluids and an engineer is properly spent, for those who consider it like insurance coverage it makes extra sense, the one time you want it is whenever you don’t have it. Ought to the installation of the product fail on account of poor fluids administration the cost of a getting it flawed are outweighed by getting it right.
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four. What technological developments are anticipated for HDD gear in the subsequent a number of years?
Vos: We anticipate a number of areas of know-how improvement for the subsequent few years. Firstly, there’s fixed research and improvement of better and various steering methods offering elevated accuracy, tighter steering tolerances and reliability of borehole location at vital depths. Secondly, the enhancement of other technologies in recent times are capturing a share of the former HDD market and we anticipate to see a response from the HDD business to aim to compete in this phase. This will embrace bigger diameter pilot holes, hybrid strategies that permit quicker reaming and a consistent and reliable technique to scale back the danger of inadvertent fluid release to floor.
Dalgleish: Finding gear will proceed to evolve, current introductions like multiple frequency walkover techniques to handle passive, lively interference and incorporating GPS coordinates into a bore document for example. The subsequent era of walkover finding techniques (unsure what they are going to be referred to as) which are being developed won’t have an operator on the receiver. Solidification techniques are going to be more commonplace because the dumping of pothole and drilling fluids develop into extra pricey. As part of the prices concerned with vacuum excavation/fluids restoration, small rig recycling techniques for drill rigs lower than $100,000 will turn out to be more prevalent.
5. What are the essential dangers/opportunities house owners need to think about before choosing HDD for his or her tasks?
Allouche and Murray: Pipeline security and integrity is essential to house owners who attempt to guard the setting and communities inside the footprint of their linear undertaking. HDD installations are effective, low-impact solutions which are feasible inside a wide range of underground circumstances. Nevertheless, HDD has specific limitations that may present vital development dangers. Since HDD requires a fluid-filled bore requiring pumping strain for production, understanding the subsurface circumstances along the drill path alignment is essential in the course of the design part to determine and mitigate potential challenges throughout design and development. Potential dangers (e.g., coarse granular formations, perched/artesian aquifers, high reactive soils, coal seams) might be significantly decreased if an skilled trenchless workforce investigates the location, designs the HDD contemplating the subsurface circumstances and the contractor utilizes the appropriate instruments, strategies and monitoring technologies to reinforce HDD execution, while maintaining inadvertent return response and contingency plans throughout development.
A collaborative danger management course of initiated by the owner in the course of the preliminary design part and carried by way of the investigation, detailed design and development phases presents the very best opportunity for profitable completion of the HDD venture. Recognized dangers may be either prevented, mitigated, assumed or transferred, based mostly on bodily/environmental constraints and the proprietor’s danger profile.
Dalgleish: All tasks have danger and utilizing HDD doesn’t remove them. The chance is the power to navigate underground, which allows for the set up of product in areas the place the normal open-cut can’t achieve access. Typically, the top users are unaware that an HDD venture has even taken place. A few of the further advantages are a decreased carbon footprint, uninterrupted visitors move, and rehabilitation costs which might be enormously decreased. The risks reminiscent of inadvertent returns or the failure to efficiently install the product the first time are outweighed by the benefits of utilizing HDD.
Vos: Every venture comes with its personal set of risks and alternatives. As the trenchless marketing consultant, it is very important understand and communicate these risks and alternatives to the stakeholders and then handle improvement and execution appropriately. It will be significant that house owners contemplate tasks as associated to HDD geometry, subsurface circumstances and environmental sensitivities. One of many challenges we face is when tasks are constrained with fastened routes to avoid several smaller obstacles in a single space, resulting in a geometrical, geological, or environmentally troublesome HDD crossing in another. It is very important notice that a longer HDD isn’t necessarily a harder or pricey crossing, which is a standard false impression when venture alignments are being established. Alternatives typically exist to increase a crossing length with a view to achieve a big discount in HDD complexity and price.
“Meet the Specialists” is a new function in Trenchless Know-how Canada written by Keivan Rafie, P.Eng., PMP, ENV SP, PE, CDT, lead tunnel engineer at Stantec. The features embrace leaders in the trenchless subject discussing quite a lot of points and challenges dealing with the business in Canada.