On account of several benefits, trenchless technology is becoming the first choice in many construction projects. Dr Niranjan Swarup elaborates more on the importance, benefits and demand trends of this technology in India.
Trenchless technology is one of the most important tools for developing, maintaining, and managing subsurface infrastructure while protecting the existing built infrastructure and natural habitat. Trenchless is the only sustainable solution available to address the increasing service demands of a burgeoning urban Indian population with an ever-reducing availability of urban spaces. Today, several government initiatives for building and maintaining the physical infrastructure are in different stages. While some of these are completed, several others are still under development. Importance of trenchless technologies in the current scenario has grown substantially as the available spaces are reducing fast. The technology application, however, is a state-of-the-art process and there are different methods and equipment used in trenchless construction for meeting a specific challenge. If appropriate technique is applied, trenchless provides several advantages and the utility owners need to be aware of suitable trenchless technologies to realise such advantages. In India, this application is taking place on a feverish pitch and the current trends of trenchless technology adoption would define the new opportunities and challenges for stakeholders and given the size of Indian construction industry, this is going to determine the future of trenchless technologies in the world. Through this article, we shall be tracing the above canvass and attempting to provide an actionable brief to the reader.
Importance of trenchless technology
Trenchless technology is defined as the branch of applied engineering that deals in the processes and techniques essentially used to develop, maintain, or manage subsurface infrastructure without excavating continuous trenches. The primary aim of resorting to the application of this technology is to conserve the existing habitat as best as possible by preventing damages. In urban areas, due to burgeoning service demands and ever shrinking working spaces, the technology is gaining significance in the overall infrastructure development and management activities.
It can be observed that at one hand, the aggregate net present value of the physical infrastructure built in the last 25 years outstrips the cumulative NPV of the infrastructure developed till then. All of such existing assets have a large proportion of buried components and structures that are continuously deteriorating and needing trenchless intervention. Added to this, the new infrastructure being built under several developmental programs like smart cities, AMRUT, Namami Gange, and several other initiatives where subsurface constructions are substantively large and needed to be executed in densely populated urban settings.
Servicing the rehabilitation and retrofitting demands all existing built assets on one hand and building newer structures in densely populated and congested environs on the other, is becoming increasingly challenging and difficult. The operations are now assuming unmanageable proportions where conventional construction methods are somewhat becoming ineffective and trenchless gaining more acceptance. The caption, 'underground is the future and trenchless is the way forward', can sum up the current scenario in construction industry.
Methods and equipment
Trenchless technology activities can be categorised into four different sectors. Techniques to create new subsurface structures - New Installations; Techniques to rehabilitate and retrofit an existing buried network - Rehabilitation Techniques; Techniques to replace an existing dilapidated buried structure where rehabilitation will be ineffective or impossible - Replacement; and the last, but quite important part, the subsurface strata and structure evaluation and reporting techniques that provide essential information for avoiding utility damage and accidents.
If we look at actions involved in New Installation techniques, the primary aim is to create a continuous subsurface cavity and install a liner to prevent cavity collapse. To achieve this, we need to displace soil from its original location. This displacement could be done in three distinct manners or in combinations thereof, transfers to the line of cavity, axially forward, and axially backward. Equipment to achieve this are moles that work pneumatically, augurs that rotate and cuts the ground through applied torque, directionally controlled drills that again cut the grounds through rotary drilling and removing the excavated materials through slurry transport, and shielded tunnelling or micro-tunnelling that cuts the ground by a full face cutter head and soil transport system comprising slurry system or solid conveyance system like conveyors. Cavity protection is achieved through installation of liners, either through pullback in the cavity or through jacking therein. All tunnelling works are done remotely and therefore signal transmission through the subsurface is an important and essential portion of equipment operation system. In addition to the main cavity creation equipment, there are several ancillary equipment like slurry making units, pumping units, waste management and disposal units, energy generators, and likewise. On the similar lines, in rehabilitation segment, the primary purpose is to arrest the deterioration process of buried structures and rehabilitate them for enhancing the economic life. In trenchless technology, this applies to pipelines and aims are to prevent hydraulic, structural, operational, or environmental failures. For hydraulic rehabilitation, the actions are to install a membrane at the location of leakage. For structural rehabilitation, the actions are to install stronger liners capable of withstanding acting loads, while for operational and environmental rehabilitation, the actions are to rectify the malfunctioning portions of pipelines by clean-ups and minor repair works. Again, like new installation, the intent would be to pull a liner section in buried pipe, push a liner section or form the liner in place. Equipment therefore, are for pulling liners like winches, jacking units, liner winding mandrels, CIPP insertion and curing systems and likewise. Also, there are equipment to render ancillary services like CCTV robots, boilers and several more as per the needs and requirements of the technique.
When we talk about replacement, the idea is to replace the existing pipeline liner material by a new liner. This is done through either bursting the line from inside, imploding the liner material, or extracting the liner material by pulling the pipe. The replacement pipe is generally pulled in the created cavity. Equipment therefore are bursting tools that crack and burst pipes by pulling or pushing of an oversized bursting tool or are microtunnelling shields that are of larger diameter when compared with the old pipe, or are winches that pull out the pipes or replacement tool.
The last sector of the trenchless technology profession is the strata and buried structure health evaluation techniques. Strata information helps in deciding the technology selection and positioning of the new utility within the right of way permitted for the specific work. Failure to acquire this information leads to project failures of varying levels starting from minor route deviations, to damages of the existing or new structures, to even complete project failure. Information gathering and its proper application in projects, therefore, is one of the most important requirements for the success of new installation trenchless projects. Buried structure health is equally important for rehabilitation and replacement works. For avoiding subsurface strata damage, the latest system in use is Subsurface Utility Engineering (SUE) wherein the information about buried utilities are gathered in a systemic manner with different quality levels, termed as D, C, B, and A. The equipment usage starts from level C, and the equipment include total station, DGPS, and other survey equipment. In level B, pipe and cable locators, induction locators, ground penetration radars form the core of equipment. Finally in level A, vacuum excavators and small hand excavation tools are used. Other investigation segment is of pipeline condition assessment where integrity status of buried pipelines are investigated and errors are diagnosed. Although there are several equipment used in India, for trenchless applications, one of the major equipment is the CCTV camera that is used for getting the internal images of pipelines. Though the output is information about the internal pipeline surface only with no details about the external pipe surface, the reports are quite useful in the pipeline health assessment. One last set of investigative techniques is aimed at gathering information about subsurface strata, and the most common equipment include geotechnical investigation equipment.
Trenchless technology, as the name indicates, is about less trenches. This means while executing a project work, one will be excavating less amount of trenches. Naturally the possible destruction of on-ground as well as close-to-surface underground structures is avoided to a large extent. In Indian settings, where the congestion is at peak, this working system is a boon for utility project owners as the need to acquire larger right of way can be avoided successfully. Further, there are certain project constraints, that are impossible to overcome in conventional construction methods. Trenchless comes to rescue of the stakeholders in all such cases. In addition, as the quantum of excavation is reduced, project execution timeframe also gets reduced, leading to leaner projects. Environmentally, the projects have smaller footprints. So, if one wants to achieve such benefits, applying trenchless is a better option.
It can be never less emphasised that the precision and quality of a properly executed trenchless project shall always be much better when compared with conventional construction methods. In fact in some projects, trenchless is the only possible option if the strata or the existing buried utilities make open cut excavations impossible.
Current trend in trenchless technology adoption
Trenchless technology on account of several benefits is becoming the first choice in many projects. Currently, the trend of experimentation has also started. We have observed that recently a few projects that were suitable for certain type of trenchless technique, has been attempted through other less expensive methodologies, again trenchless. Some of such projects have even succeeded and the engineers are experimenting with such rewarding experiences. The impediments, however, are the shortage of skills in such engineering professionals leading the delays and project failures. Another difficulty dogging the Indian trenchless industry is the lack of good quality construction equipment leading to failed projects. For the last two decades, Indian Society for Trenchless Technology (IndSTT) is the apex organisation of trenchless industry in India and is creating systems, guidelines, criteria, specifications, code documents etc for overcoming such impediments. Efforts of IndSTT are now yielding results with the flagship event, NoDig India Show 2018 getting all global eyeballs, ten renowned Keynote Speakers joining the event, three new codes under development, taking the total number of codes to eight, a new schedule of rates and several more initiatives.
Opportunities and challenges
With such a demand, where the cumulative annual investments in subsurface construction exceeding a few billions of US Dollar, the market is somewhat exploding. The demand coupled with available work fronts provides immense opportunities for development of newer variants of trenchless techniques and their refinements at one hand and reduction of costs of several techniques over the years. IndSTT has been documenting such cost optimisations for quite some time and has published 10 editions of Schedule Rates for Construction Contracts Employing Trenchless Technology, with the next edition slated to be released in December 2018 during the NoDig India Show 2018.
The challenges facing the industry also are immense, one is the possibilities of ill-directed technology growth that could lead to profiteering and unfair practices. Another issue would be application of technology by unworthy individuals leading to inappropriate usage of technology and poor installations. An example of this situation is the subsurface utility engineering. The process requires evaluation of subsurface strata in a systematic manner. In case the individual cuts the corners and avoids a few specific steps, he would miss out on a complete range of sources of information, leading to incomplete inputs essential for a safe and sound installations. Possibilities of accidents could never be ignored therein. What we need is adequately skilled professionals and if we don't create such individuals, the failure could be a very near possibility.
Such challenges need to be contained and IndSTT is working towards that end. IndSTT recently concluded a set of training workshops on SUE. In this training, IndSTT has trained about 99 individuals. Out of them, 14 individuals were provided distinct seals to certify the SUE plans and information as they could complete level 2 and 3 and clear the test. IndSTT is working towards create more professionals in SUE as well as in other fields.
Future of trenchless techniques in India is quite bright as the demands are on upswing. The need is to have proper framework, manpower, and equipment base for proper technology implementation in India. The space available for discussing these points in this article was a little short and therefore, we shall be covering such points in details in the coming edition. We invite the reader to interact with IndSTT to personally take the matter forward.
Future of trenchless techniques in India is quite bright as the demands are on upswing.
Dr Niranjan Swarup is the Director General of Indian Society for Trenchless Technology (www.indstt.com), the apex organisation of trenchless industry in India.