Tunnel boring machines (TBM) have been used for the construction of long tunnels for more than 70 years and their use has included several long tunnels for hydropower and civil infrastructure projects. Most of the major mountain ranges in the world including the Alps, Andes, Caucasus, Himalayas, and Rockies where several hydropower projects have been built and continue to be planned are associated with high overburden and challenging geotechnical conditions for the construction of long tunnels.
The historical use of TBMs in the Himalayas was hampered with challenges, some of which were due to specific aspects that were not directly related to geotechnical risks but rather the inappropriate type of TBM for the prevailing geological conditions. Goel (2014, 2016) presented several challenges and lessons learned associated with the first series of TBMs that were attempted to be used in the Himalayas from the late 1980’s to the late 2000’s.
Given that there have been some very positive results within the past decade and in particular, most recently with some ongoing projects, it is considered to be warranted to document a fresh perspective for the use and applicability of TBMs in the Himalayas since improved technical evaluations and risk management practices have provided success. The past tendency to shy away from the application of TBMs due to actual problems encountered and/or perceived risks should now be challenged with the optimism of the success realized in recently completed and currently ongoing projects.
Key risks and challenges for TBMs in the Himalayas
Geological conditions – faults/abrasivity/inflows
The Himalayas are the most geologically complex mountain range in the world where hydrostatic upward/uplift movement continues due to the ongoing collision of the Indian and Eurasian tectonic plates and over past time has resulted in some areas of highly disturbed geological formations. The Himalayas can be described with general geological regions of sub-Himalayas, Lesser, and Higher/Greater Himalayas that are separated by the major regional thrust faults of the Main Boundary Thrust (MBT) and Main Central Thrust (MCT). The Sub-Himalayas and Lesser Himalaya regions are generally associated with sedimentary rock formations with limited disturbance whereas the Higher/Greater Himalaya region is generally associated with crystalline and metamorphic bedrock (granites, schists, phyllites, quartzites) with extensive disturbance with folding/tilting of the main rock formations, extensive faulting and fracture zones and high abrasivity. Undisturbed zones also exist within the Higher/Greater Himalaya. There exist prominent bedding of the metamorphic rock units often representing zones of disturbance as geological faults and significant fracture zones as presented in Figure 1.
While the various rock formations can be present in massive zones of great thicknesses, thin low strength zones of schists and phyllites can be present throughout the Higher/Greater Himalaya. With the prominent bedding of the various rock formation there is the presence of frequent geological faults and fracture zones that can vary in thickness up 10’s of meters and are commonly associated with very large inflows/inrushes with fines. Mauriya et al. (2010) present a useful discussion on the challenges and strategies for tunneling projects in the Himalayas based on commonly recognised risks.
Geotechnical conditions – in situ stresses
The Himalayas are the highest mountain range in the world and thus there exists the highest overburden with high in situ stresses whereby the hydropower tunnel alignments may be subjected to elevated in situ stresses resulting in overstressing including rockbursting as well as squeezing where weak zones are present since they are either sub-parallel to valleys or pass below major mountain ridges with deep cover. Given the varied geological conditions of the Himalayas, it can be expected that the in situ stresses will vary significantly and therefore site-specific stress testing should be performed. In situ stress testing has been completed for many past projects comprising both hydraulic fracturing and overcoring typically in the area of the pressure shafts, powerhouses, and valley crossings as presented by Kumar et al. (2004). Low in situ stresses may also be apparent below low topographic ridges which may influence the stability of large span powerhouses as experienced in Bhutan (Dorji et al., 2024). Swannell et al. (2016) present a useful summary of past in situ stress testing in the Himalayas (mainly in India) that was considered as part of the loading conditions for the pre-cast segmental lining for the Kishanganga headrace tunnel. Brox and Piaggio (2025) present the results of deep in situ stress testing from both past and recent projects whereby higher than expected in situ stresses were measured, in particular in regions of nearby plate tectonics, and which therefore should be considered for similarly sited deep headrace tunnels for hydropower projects. Finally, Panthi (2012) reviewed the probable in situ stresses along the TBM excavated section of the headrace tunnel at the Parbati II hydropower project with a maximum cover of 1500 m and concluded that elevated in situ stresses were likely present to have contributed to the cause of rockbursting.
Logistics – access/power/spoil
Other important risks are related to TBM logistics including access for mobilization, power supply and spoil disposal. Most hydropower projects are located in remote mountainous areas where existing roads may be of limited quality including bridges of limited capacity and therefore significant upgrades may be required for the mobilization of a TBM. The power demand for TBMs can be appreciable and vary up to 10 MW for very large TBM diameters and therefore an adequate power supply must be established and maintained either by a connection to an existing powerline for example from an existing nearby power station, or by the use of generators with diesel consumption. Major cost savings can be realized with a connection to an existing powerline that requires the early installation of a transformer as was done at the Pakal Dul hydropower project as presented in Figure 2. Finally, there may exist strict environmental restrictions within a project region for the safe disposal of spoil. TBM spoil from competent bedrock comprises variable size chips ranging from a few centimeters up to 15 cm in length which can be effectively utilized for road sub-base material or well-drained backfilling for alternative construction purposes.
Historical TBM tunnels in the Himalayas
Dul Hasti (1989) – India
The 390MW Dul-Hasti hydropower project included a 10.6km headrace tunnel with a maximum cover of 1250 m and was the first project in the Himalayas where a TBM was used. Construction commenced in 1989 and was expected to be commissioned in 1995 but was delayed to 2007 due to various contractual challenges. A 6.75 km upstream section of the headrace tunnel was planned to be excavated using a TBM due to the lack of a practical access adit. However, only approximately a total of 2.9 km of the upstream 6.75 km section of the headrace tunnel was completed using an M/S Robbins 270 series open face hard rock TBM of 8.3 m diameter with 432 mm (17”) cutters. The actual conditions encountered were reported to be much more adverse than expected and there was the occurrence of the blow out of probe holes that resulted in inflows up to 1100 l/s with appreciable sand and silt as well as higher than expected cutter consumption in the quartzites. Figure 3 presents the longitudinal profile of the tunnel.
An overall progress of only 86 m/month was achieved by the original contractor which reduced upon removal of the contractor and taking over by the project client. The use of the TBM was abandoned since the achieved progress by drill and blast was nearly double.
Parbati (2002) – India
The 800MW Parbati-II hydropower project included a 31.5km headrace tunnel with a maximum cover of 1600 m and was the second project in the Himalayas where a TBM was used for a 9 km central section of the headrace tunnel. Construction commenced in 2002 and faced several construction challenges, including cloudbursts, flash floods, and rockbursts. Commissioning was finally performed in 2025.
Approximately a total of 2 km of the central 9 km section of the headrace tunnel was completed using an Atlas Copco Robbins MK-27 open face hard rock TBM of 6.8 m diameter with 432 mm (17”) cutters. The portion that was completed comprised mainly granitic gneiss where significant overbreak occurred that could not be supported with traditional pattern bolts and rather required the installation of continuous ring beams that appreciably reduced progress. After two years of limited progress the TBM manufacturer was called in which improved progress to as much as 250 m/month. Upon the intersection of the massive quartzite there was the occurrence of severe rockbursting at a depth of 1100 m with the loss of life and in 2007 the TBM encountered a water bearing zone within the quartzite under a cover of 900 m with 120 l/s (1700 gpm) of inflows including sand and silt that buried the TBM and three years passed during which time was needed to control the inflows but overall resulted in the abandonment of the TBM. Figure 4 presents the longitudinal profile for the Parbati hydropower tunnel (Panthi, 2012, Clark and Chorley, 2014).
TBMs were also used at the Parabati II project and successfully completed the construction of the twin, 1.5 km long, inclined pressure shafts with a 4.88 m diameter double shield TBM through the prevailing granites with pre-cast concrete segmental linings as shown in Figure 5.
Tapovan (2008) – India
The 520MW Tapovan hydropower project includes a 12.1 km headrace tunnel and was the third project in the Himalayas where a TBM was used for an 8.6 km portion of the headrace tunnel. Construction of the headrace tunnel commenced in late 2008 and typically achieved 500 m per month for the first year using a 6.5 m diameter double shield TBM with a 300 mm thick pre-cast concrete segmental tunnel lining (PCTL) with an internal diameter of 5.6 m.
The geology along the headrace tunnel includes the Central Himalayan Crystalline series with mainly quartzites, gneisses, augen gneisses and mica-schists with multiple small and large shear zones and faults with geothermal groundwater and the alteration of the schists and gneisses to clays. Figure 6 presents the longitudinal profile of the headrace tunnel showing the complex geology.
Difficult conditions were encountered after about one year of TBM excavation at about chainage 9000 m with the instability of wedge block at the face of the TBM that resulted in the stoppage of the TBM along with the inrush of water and fines up to 800 l/s along with the failure of a portion of the PCTL ring. A 180 m long bypass tunnel was constructed around to the front of the TBM to rehabilitate the area and allow for continued TBM excavation and the total downtime for this was about 8 months. Second and third TBM entrapments occurred in early and late 2012 after another 3000 m of excavation at prior to chainage 6000 m. All of these significant TBM stoppages appear to have occurred near the intersection of inferred fault/fracture zones with very acute angles to the tunnel axis despite the entrapment mechanism has been presented as a result of sub-vertical faults (Brandl et al., 2010 and Millen and Brandl, 2011) The TBM has remained entrapped since the third entrapment in late 2012 with multiple unsuccessful attempts to re-start the project.
Kishanganga (2011) – India
The 330MW Kishanganga hydropower project includes a 23.7 km headrace tunnel and was the fourth project in the Himalayas where a TBM was used for a 14.75 km portion of the headrace tunnel. Construction of the headrace tunnel commenced in April 2011 and was completed in June 2014 (38 months) and typically achieved an overall average of 12.5 m/day or about 400 m per month but with a maximum monthly progress of 812 m using a 6.2 m diameter double shield universal (DSU) TBM with 483 mm (19”) cutters and a 350 mm thick pre-cast concrete segmental tunnel lining (PCTL). The TBM was specifically designed by the TBM tunnel contractor (SELI) based on extensive experience in difficult tunneling conditions and including key design features to allow for de-risking and continued advance through challenging conditions. Figure 7 presents the longitudinal tunnel profile where the maximum cover was 1400 m and therefore there was a recognized risk of squeezing of the PCTL.
Mixed geology was present along the headrace tunnel alignment comprising andesites, phyllitic quartzite and meta-siltstones and sandstones of variable rock quality and strength. The success of the timely completion of the construction of the Kishanganga headrace tunnel is fully attributed to the experience and competence of the TBM tunneling contractor.
Recent TBM hydropower tunnels in the Himalayas
Bheri Babai multi-purpose project – Nepal
The 47MW Bheri-Babai Multi-purpose project was the first use of a TBM in Nepal for the construction of the entire 12.2 km headrace tunnel. Construction of the headrace tunnel commenced in October 2017 and was completed in April 2019 (18 months – 12 months ahead of schedule) and typically achieved an overall average of 24 m/day or about 712 m per month but with a maximum monthly progress of 1202 m using a Robbins 5.0 m diameter double shield TBM with 483 mm (19”) cutters and a 300 mm thick pre-cast concrete segmental tunnel lining (PCTL). The TBM headrace tunnel was completed one (1) year ahead of schedule and notably passed without any delay through the Main Boundary Thrust fault that was the recognized key risk for the project. A single delay of five (5) days was experienced due to uncemented sedimentary bedrock that required the construction of a bypass tunnel to the front of the TBM for liberation. Figure 8 presents the space required for the assembly and launch of the TBM at the Bheri Babai headrace tunnel.
Sunkoshi-Marin multi-purpose project – Nepal
The 39MW Sunkoshi-Marin Multi-purpose project was the second use of a TBM in Nepal for the construction of the entire 13.3 km headrace tunnel. Construction of the headrace tunnel commenced in October 2022 and was completed in May 2024 (19 months) and typically achieved an overall average of 25 m/day (maximum 67 m/day) or about 750 m per month but with a maximum monthly progress of 1224 m using the same Robbins TBM from the Bheri-Babai project with an enlargement of the cutterhead to 6.2 m diameter for the double shield TBM with 483 mm (19”) cutters and a 300 mm thick pre-cast concrete segmental tunnel lining (PCTL). Figure 9 presents the longitudinal tunnel profile where the maximum cover was 1250 m and therefore there was a recognized risk of squeezing of the PCTL.
The TBM headrace tunnel also notably passed without any delay through the Main Boundary Thrust fault that was the recognized key risk for the project. A single delay of twenty-one (21) days was experienced due to a weak phyllite zone that required the construction of a bypass tunnel to the front of the TBM for liberation. (Home and Shrestha, 2023).
Neelum Jhelum hydropower project – Pakistan
The 969 MW Neelum Jhelum hydropower project was the first use of TBMs in Pakistan for the construction of the twin 10 km sections of central portion of the 28.5 km headrace tunnel with a maximum cover of 1900 m being the deepest tunnel in the Himalayas. Construction of the TBM sections of the headrace tunnel commenced in March and April 2013 and were completed in October 2016 and May 2017 respectively. Geology along the central section of the headrace tunnel comprised the Murree Formation of intermixed sandstones, siltstones and mudstones with poor quality and durability of the mudstone zones. A major rockburst was experienced in one of the TBM drives upon the intersection of a massive sandstone zone located before the area of maximum cover but with a cover of 1300 m where the in situ stress ratio was measured at k=2.9 resulting in a delay of 6 months since severe damage occurred to the TBM.
The TBMs were Herrenknecht 8.5 m diameter open gripper type whereby the headrace tunnel was designed and constructed as a one-pass approach with the initial support installed within the L1 section ahead of the grippers and the final shotcrete lining was constructed within the L2 section some 65 behind the face using shotcrete robots. TBM progress was hampered by elevated in situ stresses that resulted in frequent overstressing including rockbursts and averaged about 8-10 m/day. The one-pass design and construction approach was associated with some shortcomings in terms of the quality of the final shotcrete lining and required significant remedial works (Peach et al., 2019). Figure 10 presents the final shotcrete lining of headrace tunnel.
Current TBM hydropower tunnels in the Himalayas
Vishnugad Pipalkoti – India
The 444 MW Vishnugad Pipalkoti hydropower project is currently in construction and includes a 12.3 km headrace tunnel. Construction of the headrace tunnel commenced originally in late 2016 with the excavation of the TBM starting portal. However, it immediately became apparent that bedrock was not present at the designated TBM portal area but rather partially consolidated river deposits that required a specially designed and built launch cavern with heavy grouting. Unfortunately, the initial launch cavern was not effective to allow for the launching of the TBM and a total delay of six (6) years was realized before the TBM broke into bedrock after 200 m (Kahli and Potnis, 2023). Figure 11 presents the TBM portal area during the initial excavation in 2016 when partially consolidated river deposits with boulders were discovered without bedrock.
The TBM comprises a specially designed Terratec 9.0 m diameter double shield universal (DSU) TBM (similar to Kishanganga TBM) in conjunction with a 350 mm thick pre-cast concrete segmental tunnel lining (PCTL). This new TBM design was targeted to improve the TBM capability to advance through squeezing/converging rock formations under high cover, the telescopic joint design (allowing by such to operate the machine in double shield mode in very weak rock), and the capability of the TBM to investigate and treat the ground around and ahead of the tunnel face (Grandori, 2016). Geology along the headrace tunnel alignment comprises predominantly slates with dolomitic limestone. TBM excavation finally commenced in July 2023 and since April 2024 has progressed consistently at about 11 m/day or 365 m per month.
Pakul Dul – India
The 1000 MW Pakal Dul hydropower project is currently under construction and includes twin, 7.5 km headrace tunnels. Construction of the headrace tunnels started in November 2023. Two, Herrenknecht 7.2 m diameter single shield TBMs are being used in conjunction with pre-cast concrete segmental linings (PCTL). Geology along the headrace tunnel alignment comprises mixed quartzites, phyllites, schists, and gneissic granites. Figure 12 presents the TBM at the starting portal platform that was assembled and launched in a very limited area which has been successfully managed for TBM logistics during construction.
TBM progress has been exceptional with the recent progress in early 2025 of 630 m in a single month and 46.6 m in a single day. The success of the technical evaluation to use a TBM for the Pakal Dul project along with the TBM procurement has been attributed to comprehensive risk management practices with all stakeholders (Armetti and Panciera, 2023).
Proposed TBM hydropower tunnels in the Himalayas
A TBM is also planned to be used on the 285 MW Upper Tomar Hydropower Project in Eastern Nepal that includes an 8.7 km, 7.2 m diameter headrace tunnel. This constitutes the first TBM to be used for a private hydropower project in Nepal and the formal contract was signed for this project in mid-2025 to use for the third time the same Robbins double shield TBM with the same tunnel contractor who constructed both the headrace tunnels of the Bheri Babai and Sunkoshi-Marin Multiple-purpose projects. Figure 13 presents the longitudinal profile for the proposed headrace tunnel.
In addition, the Melamchi Water Supply Project – Phase 2 in Nepal (that includes for a min-hydro station) includes the 8.9 km Yangri Tunnel with a maximum cover of 1700 m which has been evaluated for the application of TBM construction given that there is no possibility for an intermediate access adit and with difficult portal locations for access (Brox, 2022). Figure 14 presents the longitudinal profile for the proposed Yangri tunnel.
Other relevant TBM projects in India
Rishikesh-Karanprayag Rail Tunnel Project
The Rishikesh-Karanprayag rail project has been in construction in the Himalayan foothills since late 2022 and includes two tunnels (upline and downline) of lengths of 10.5 km and 10.3 km. The area is dominated by metamorphic rocks, including schists, gneisses, and quartzites. Twin, 9.1 m diameter single shield TBMs have been used in conjunction with pre-cast concrete segmental lining (PCTL). The TBMs were specifically designed with accessories for overcoming the risks of squeezing conditions and include a cutterhead torque box, high thrust rams, and shield void measurement system. Progress achieved an average of 630 m per month with a maximum of 555 m with sustained daily progress of 12 to 18 m and a maximum daily progress of 39 m (Cooper, 2025).
AMR and Veligonda Water Transfer Projects
The Alimineti Madhava Reddy (AMR) water transfer and supply project comprises a single, 10m diameter, 46 km tunnel located in southeast India in the state of Andhra Pradesh that transfers water below a Tiger Reserve from the Srisailam Reservoir to an area of farmland to the north. In addition, the Veligonda water transfer and supply project comprises 7.9 m and 10 m diameter, 19 km tunnels located immediately south of the AMR project. Both projects have used Robbins double shield TBMs as well as a double shield Herrenknecht TBM in conjunction with pre-cast concrete segmental linings (PCTL). The geology along these tunnel alignments has comprised very strong (250-450 MPa) and abrasive quartzites that has hampered TBM progress to about 250 m per month (Harding, 2010). The north TBM drive of the AMR project recently experienced a major inrush of weak and soft material that resulted in multiple fatalities and the rotation of the back up of the TBM which may not be salvageable.
TBM types and risk mitigation requirements
TBM types
Hydropower tunnels are generally sited in mixed and competent bedrock and face-pressurized TBMs operated in close mode are generally not required. The typical types of TBMs used for hydropower tunnels are:
- Open gripper with traditional rock support;
- Single Shield with pre-cast concrete segmental lining;
- Double Shield with traditional rock support, and;
- Double Shield with pre-cast concrete segmental lining.
However, it should be noted that geotechnical conditions often associated with geological faults comprising highly fractured and/or soft clay gouge with elevated groundwater pressures or within unique geological formations such as highly permeable lahar warrant the use the face-pressurized or hybrid types of TBMs operated in close mode for such limited sections when encountered along a long and deep hydropower tunnel.
TBM evaluation and selection criteria
A comprehensive technical evaluation must be undertaken for the selection of the most appropriate type of TBM to be used for the construction of headrace tunnels for hydropower projects given the severe impacts that may arise from the various prevailing geological and geotechnical risks. Grandori et al., (2018) and Brox (2020) present and discuss the various geotechnical and logistical aspects that should be considered as part of a TBM evaluation and selection process including the following:
- Rock Types and Distribution
- Geological Faults and Weak Zones
- Geological Synclines and Anticlines/Folding
- Durability of Rock and Final Lining Requirements
- Squeezing Potential
- Overstressing Potential including Rockbursting
- High Groundwater Inflows, Pressures and Temperatures
In addition to the important geotechnical aspects there exist multiple logistical and other aspects that require a careful evaluation including access for mobilization, portal space availability, power availability, environmental spoil disposal requirements, and contractor experience. Brox (2021) presents a TBM selection criteria logic chart of the key technical aspects to highlight the typical selection process as presented in Figure 15.
TBM risk mitigation
The key risk mitigation requirements related to the use of TBMs for the construction of headrace tunnels for hydropower projects are that adequate geotechnical investigations and planning are performed well in advance during the early study stages of a project. While the challenges of high elevation and deep drilling are recognized for mountainous regions, alternative methods of investigations including geophysical investigations and detailed surface mapping with representative rock block testing for strength, petrology and abrasivity since many of the rock units within the Himalayas contain a high content of quartz which can have a significant impact on TBM progress and operating costs.
The key risk mitigation requirements related to the use of TBMs for the construction of headrace tunnels for hydropower projects are that adequate geotechnical investigations and planning are performed well in advance during the early study stages of a project. While the challenges of high elevation and deep drilling are recognized for mountainous regions, alternative methods of investigations including geophysical investigations and detailed surface mapping with representative rock block testing for strength, petrology and abrasivity since many of the rock units within the Himalayas contain a high content of quartz which can have a significant impact on TBM progress and operating costs.
An important risk mitigation approach for TBM hydropower tunnels is the adoption of the well recognized approach of one-pass pre-cast concrete segmental linings (PCTL) that have been used and successfully completed for more than 925 km of hydropower tunnels (Brox and Grandori, 2023). PCTL offers greater safety to workers during construction with protection from the impacts of high in situ stresses (e.g. rockbursting) but not from sudden inrushes through the face. The current TBM hydropower tunnels in the Himalayas further confirms this low-risk construction approach. Figure 16 presents the pre-cast concrete segmental lining installed at the Bheri Babai headrace tunnel.
Finally, the potential risk for overstressing including the prediction of the expected spatial occurrence of rockbursting can be evaluated using the method presented by Brox (2012, 2013) that has been based on and verified by numerous case projects of deep tunnels where significant overstressing and rockbursting was realized. Such an evaluation should be a fundamental part of a due diligence technical assessment to safety related construction risks to be presented in a geotechnical baseline report and contract documents as part of full and total disclosure of project risks for tender.
Environmental/social advantages for TBMs
Many of the hydropower projects that previously have been and continue to be constructed across the Himalayas are sited within valleys where there exist well established communities both at upper elevations as well as along lower elevations adjacent to rivers. Accordingly, these communities, including the associated infrastructure of houses, schools, clinics, and other important infrastructure including water wells and springs may be at risk during the construction of headrace tunnels by blasting that may induce vibrations to overlying structures resulting in damage as well as causing stress relaxion inside the tunnels resulting in the opening of major fractures and geological faults that may significantly reduce the original groundwater table during construction which may not fully be re-established after construction and during future pressurized operations. TBMs offer a more environmentally acceptable solution without vibrations and also less relaxation around a headrace tunnel to limit the impact to the groundwater table. Figure 17 presents the very large inflows that occurred during the construction of the 15.3 km headrace tunnel at the Uma Oya Multi-Purpose project in Sri Lanka along with the reduction of groundwater table that resulted in subsidence and damages to houses at surface.
Lessons learned for future TBM use
The following conclusions and lessons are considered to have been learned based on historical and recent TBM hydropower tunnel projects in the Himalayas:
- Long hydropower tunnels are finally getting completed using TBMs in the Himalayas at some very remote project sites after some good planning, lessons learned, and improved technology;
- The sedimentary geology of the Lesser Himalaya is less disturbed and has allowed for greater than expected TBM progress for the early completion of multiple projects, notably in Nepal to date:
- A well-experienced and competent TBM tunnel contractor and TBM labour crews are required for the successful timely completion of any headrace tunnel associated with challenging geotechnical conditions whereby special experience is typically called upon for unique solutions
- The geotechnical conditions at the TBM portal must be confirmed with comprehensive geotechnical investigations to avoid adverse conditions for the timely launching of a TBM
- TBMs are capable of safely constructing very deep and long tunnels with the installation of conventional rock support but with impacts of elevated in situ stresses
- The most prudent approach for the construction of hydropower tunnels using TBMs in the Himalayas is in conjunction with pre-cast concrete segmental lining which provides safety to workers from high in situ stresses
- Special design features/components including high torque and thrust capacity are required for TBMs to be successfully used in the Himalayas to cope with the challenges of the geotechnical conditions
- Good planning and risk management practices have proven to be effective in contributing to the success of the use of TBMs in the Himalayas
Author details
Dean Brox of Dean Brox Consulting Ltd. Vancouver, Canada. https://www.deanbroxconsulting.com/
References
Kumar, N, Varughese, A., Kapoor, V.K., and Dhawan, A.K. 2004. In Situ Stress Measurement and Its Application for Hydroelectric Projects – An Indian Experience in the Himalayas. SINOROCK2004 Symposium, Int. J. Rock Mech. Min. Sci. Vol. 41, No. 3.
Mauriya, V.K., Yadav, P.K, and Angra, V.K. 2010. Challenges and Strategies for Tunnelling in the Himalayan Region. Indian Geotechnical Conference – 2010, GEOtrendz, IGS Mumbai Chapter & IIT Bombay
Panthi K. K. 2012. Evaluation of rock bursting phenomena in a tunnel in the Himalayas. Bulletin of Engineering Geology and the Environment, Vol. 71, pp. 761–769
Swannell, N., Palmer, M., Barla, G., and Barla, M. 2016. Geotechnical risk management approach for TBM tunnelling
in squeezing ground conditions. Tunneling and Underground Space Technology.
Khali, R.K., and Potnis, S. 2023. Construction of headrace tunnel of Vishnugad-Pipalkoti HE Project (444MW) in extreme geological conditions: Issues and challenges – A case study. World Tunnel Congress, Athens, Greece.
Goel, R.K. 2014. Tunnel Boring Machines in the Himalayan Tunnels.
Indorock 2014: 5th Indian Rock Conference 12-14 November 2014
Goel, R.K. 2016. Experiences and lessons from the use of TBM in the Himalaya – A review. Tunnelling and Underground Space Technology, Volume 57, Pages 277-283.
Dorji, T., Brox, D. and Wangdi, S. 2024. Challenges and Lessons Learned from 100 km of Major Hydropower Tunnels in Bhutan, World Tunnel Congress, International Tunneling Association, Shenzhen, China.
Brox, D. and Piaggio, G. 2025. High In Situ Stresses in Deep and Long Tunnels: Risks and Impacts, World Tunnel Congress, International Tunneling Association, Stockholm, Sweden.
Brox, D. and Grandori, R. 2023. Pre-Cast Tunnel Linings for Hydropower Tunnels: Advantages and Successes, World Tunnel Congress, International Tunneling Association, Athens Greece.
Brox, D. 2022. Melamchi Water Supply Tunnel Phase 1: Design and Construction Challenges, World Tunnel Congress, International Tunneling Association, Copenhagen, Denmark.
Brox, D. 2021. Practical Guide to Rock Tunneling, 2nd Edition, Amazon Kindle. Pages 386.
Brox, D. 2020. TBM Risk Assessment and Selection for Hydropower Tunnels, World Tunnel Congress, Kuala Lumpur, Malaysia.
Brox, D. Evaluation of Overstressing of Deep Hard Rock Tunnels, World Tunnel Congress 2013, Geneva, Switzerland.
Brox, D. 2012. Evaluation of Overstressing of Deep, Hard Rock TBM Excavated Tunnels in British Columbia. Tunneling Association of Canada (TAC) Conference, Montreal, Quebec.
Millen, B. and Brandl. J. 2011. TBM recovery under high cover and extreme water-inflow, Himalayas, India. 1st International Congress on Tunnels and Underground Structures in South-East Europe, Dubrovnik, Croatia
Millen, B., Gupta. V.K., and Brandl. J. 2010. Tapovan-Vishnugad hydroelectric power project – experience with TBM excavation under high rock cover. Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin · Geomechanics and Tunnelling 3, No. 5
Grandori, R. De Biase, A., and D’Ambrosio, M. 2018. Choice of TBM type for mountain tunnelling under very poor geological conditions: Hybrid, Slurry, EPB, DSU, Convertible TBMs, World Tunnel Congress, Dubai, United Arab Emirates.
Peach, G., Ashcroft, B. Amici, R., and Mierzejewski, J. 2019. Shotcrete Lining Installed from an Open Gripper TBM Remedial Works. World Tunnel Congress of the International Tunneling Association, Naples. Italy.
Armetti, G. and Panciera, A. 2023. Risk management process for underground works, World Tunnel Congress, International Tunneling Association, Athens, Greece.
Grandori, R. 2016. DSU TBM for Vishnugad Pipalkoti TBM Design Development for Large Diameter Rock Tunnels Under the high Covers of the Himalaya, World Tunnel Congress of the International Tunneling Association, San Francisco, USA.
Harding, D. 2010. Tunnel Boring Machines used for Irrigation in Andhra Pradesh, India. World Tunnel Congress of the International Tunneling Association, Vancouver, Canada.
Home, L. and Shrestha, A. 2023. Use of a Tunnel Boring Machine on Nepal’s First and Second TBM-Driven Tunnels in Mountainous Terrain: Sunkoshi Marin and Bheri Babai Hydropower Projects. HYDRO 2023, Edinburgh.
Panthi, K.K. 2009. Appropriateness of open TBM tunnelling in the Himalaya – A case study. Rock Engineering in Difficult Ground Conditions – Soft Rocks and Karst – Ed. Vrkljan.
Clark, J. Chorley, S. 2014. The Greatest Challenges in TBM Tunneling: Experiences from the Field, North American Tunnel Conference. Los Angeles, USA.
Cooper, C. 2025. Forging New Paths: The RVNL Package 4 Himalayan TBM Tunnel Revolution. Indian Tunneling Magazine.
