In the past few years, there has been a significant increase in tunnelling activity in the country. The rise in tunnel development in sectors such as hydropower, roads and railways has also driven the demand for tunnelling equipment. The cost of the equipment depends upon various factors including the type of tunnel construction method deployed, geological conditions and the level of technological advancements. For instance, the use of mechanisedtunnelling techniques such as the tunnel boring machine (TBM) or the New Austrian Tunelling Method (NATM) entail higher equipment costs as compared to conventional methods such as the drill-and-blast (DBM) method.
Equipment for tunnel construction is acquired either through purchase of new machinery, purchase of used/refurbished equipment or renting of equipment. The selection from among these options depends upon the availability of funds, the number of hours of work required, and the proposed timeline and work schedule. Besides, the entry of new manufacturers has widened the choice for project developers. Foreign suppliers have also set up their manufacturing or assembly units in the country, leading to lower procurement costs. However, even with the expansion of the domestic equipment market, demand far exceeds local supply and imports continue to play a critical role.
Types of equipment
DBM is the most commonly used method for tunnelling in India. Some of the key types of equipment used in this method are double boom jumbo machines (underground drilling machines), road headers (rock cutting machines for excavating tunnels) and drilling rigs (used to dig holes in the subsurface). Tunnel contractors usually prefer to purchase these machines. Some of the key suppliers in the segment include Alstom India, Atlas Copco, Texmaco Rail, Terratec and Robbins. Equipment suppliers also provide other services such as inspecting equipment on demand, providing skilled manpower for installation and maintaining inventory of spare parts. Besides, an annual maintenance contract is also offered under which the payment is made on a per metre basis and the entire risk is borne by the equipment provider.
The TBM method has also witnessed significant adoption, especially in the development of metro tunnels in congested urban areas. It has also gained prominence in the water supply and sewerage sectors. TBMs can be broadly classified into four types – soft ground, slurry, hard rock and hybrid TBMs. These machines are usually purchased by the contractors. However, as the type of TBM deployed is project specific, many manufacturers have recently started offering buy-back options. Besides, renting TBMs is another upcoming trend. Contractors, depending upon the pipeline of projects, geology and cost-effectiveness of refurbishing existing machinery, have begun renting equipment.
Tunnel contractors primarily import TBMs designed and manufactured by foreign suppliers. China continues to dominate the tunnelling equipment market followed by Finland and Germany. In 2018-19, a large number of TBMs were imported from the US as well. Major TBM equipment suppliers include Herrenknecht, Caterpillar, Hitachi Zosen, Akkerman and Robbins. In the past couple of years, TBM equipment suppliers have also started offering services such as complete logistics support, on-site first-time assembly, technical assistance, specialised manpower for maintenance of machinery and on-site excavation services as per client requests. More recently, the NATM has also gained traction. Significant tunnel length in the railway and road sectors is being developed using the NATM. Apart from excavators, loaders and tippers, the two main types of equipment used in NATM are boomers and shotcrete machines with robotic arms.
Innovations and advancements
In the past couple of years, with several tunnelling projects being undertaken in areas that have difficult geological conditions, there has been an increase in the demand for high-tech equipment. Advanced drilling systems, computerised jumbos and navigation systems are increasingly being used for greater precision and better monitoring. The navigation systems deployed in TBMs help in providing a continuous reference point for the machine’s position. Under the navigation system, a beam is picked up by the targets at the back of the TBM. This helps the driver in discerning the location and altitude on a real-time basis as compared to the planned, preprogrammed position. Further, use of the strength monitoring using thermal imaging (SMUTI) technology helps in assessing the strength of the whole shotcrete lining in real time from a secure position, bringing huge benefits in terms of safety, quality control and productivity. Besides, SMUTI can also be used during spraying to diagnose local problems such unaccelerated cold spots, pulsation and lamination effects. Moreover, the use of variable density TBMs offer increased safety and flexibility in the choice of tunnel face support and discharge of muck. These TBMs can be operated as the classic slurry TBM with an air bubble system to control the face pressure and also in earth pressure balance mode.
With the rise in tunnel construction in the country, the outlook for the tunnelling equipment market seems bright. It is, however, important to resolve issues such as shortage of skilled manpower for operating and maintaining TBMs, absence of spare parts inventory, geological surprises and inadequate investigation resulting in high wear and tear of equipment, to reduce costs and increase efficiency.