Urgent infrastructure needs in Nepal 22 Nov 2018

Shani Wallis, TunnelTalk

Hydro development was the start of underground engineering and construction in Nepal and while several new hydro projects are planned, the urgent need for water supply and irrigation, improved transportation services across the country, and aspirations for a metro system in Kathmandu are fuelling an increasing need for underground engineering and construction expertise. During a visit to the Himalayan nation, Shani Wallis, met with the President and Past President of the Nepal Tunnelling Association to understand the demand and explore how the nation is creating a national tunnelling base to meet the demands.

Despite its many rivers, Nepal has severe water demand deficiencies
Despite its many rivers, Nepal has severe water demand deficiencies

Ironically, Nepal, as custodian of the snow-capped mountains of the majestic Himalayan range, with snow melt and heavy monsoon rains in the wet season, has severe water shortages in the areas of highest need.

In the winter, when demand for electricity is highest, the hydro plants in the nation can run at only 30-35% as there is insufficient water in the rivers to run them at full capacity. Nepal currently has an installed hydro capacity of about 1,000MW and 99% of its electricity generation is hydro. There is no carbon fuel generation and solar generation is beginning to be introduced. However in the dry winter months, Nepal has a 500MW deficiency in electricity and has to import coal and carbon-generated power to meet the shortfall from neighbouring India.

Nepal Tunnelling Association

Nepal is one of the youngest Member Nations of the ITA (International Tunnelling and Underground Space Association), taking its seat at the ITA General Assembly in 2011.

The Association currently has about 100 members and six corporate members. Its executive office is registered at the offices of the IPPAN (Independent Power Producers' Association Nepal in Kathmandu.

Current Executive Committee members are:

President: Dr Gyanendra Lal Shestha
Vice President: Ram Hari Sharma
Secretary General: Kangada Prasai
Treasurer: Tara Nath Sapkota

At the last Annual General Meeting, President Shestha said: “With the wealth of knowledge available among the NTA members and through our association with ITA and the ITACET Foundation, I believe that we have a big role to plan in the many tunnelling projects required for the rapid development of the country.”

Gyanendra Lal Shestha, President, NTA (left) and Sandip Shah, Past President (right) with Shani Wallis of <em>TunnelTalk</em> center, Prajwal Man Shrestha of Mosh (far right) and Ananda Chaudhary of IPPAN (second from left) and Binaya Shrestha of Mosh (far left)
Gyanendra Lal Shestha, President, NTA (left) and Sandip Shah, Past President (right) with Shani Wallis of TunnelTalk center, Prajwal Man Shrestha of Mosh (far right) and Ananda Chaudhary of IPPAN (second from left) and Binaya Shrestha of Mosh (far left)

“We are feeling the affects also of global climate change,” explained Sandip Shah, Past President of the Nepal Tunnelling Association (NTA). “We are experiencing longer dry winter seasons and flash flooding from exceptionally heavy rainfall in the wet season.”

Nepal has an identified hydro capacity of another 83GW with 43GW of that considered technically viable. But again, ironically, the country would not be able to use that amount of power and would have to export a large percentage to neighbours India and China.

Together with hydro power development, water supply and irrigation is an urgent and growing demand for tunnelling. Further irony is that the water is sufficient in river valleys where it is not needed and dramatically deficient in valleys where it is needed. For this reason the nation is currently developing two tunnel projects – Bheri Babai and Malamchi – to redress the balance.

To the east of the country, the 12km long Bheri Babai tunnel will deliver 40m3/sec from the Bheri River valley into the Babai basin to meet its demand for year round irrigation and to maintain the groundwater resource, which is the main source of water for human consumption in the rural areas and in the city of Nepalgunj. With a hydraulic head of 150m, the project is also hosting a 48MW hydro installation.

Developing a national tunnelling base

In supporting the projected demand for tunnelling in Nepal, the nation’s Tunnelling Association is working with the ITA (International Tunnelling and Underground Space Association) and its Training and Education Foundation and Committee (ITACET) to bring the latest in tunnelling design and construction technology to a growing team of young civil engineers in Nepal.

In December, NTA in association with ITACET will hold a conference on Mulitpurpose Use of Underground Spaces and a training session on Operation and Maintenance of Hydro Tunnels . The two-day event on 13 and 14 December 2018 will be held at the Radisson Hotel in Kathmandu.

Registration fees are up to 8,000 Nepali Rupees (US$70) for Nepalese residents and USD$150 for delegates from other countries.

Contact Ms Poonam Giri for further details.

In the Kathmandu area, the Malamchi water supply project comprises three tunnels, the first at 27km long in Phase 1, and another two at 9km and 2km long in Phase 2 to tap two further rivers. The Malamchi River is the main source of water supply to Kathmandu, a city of 3 million permanent residents plus another 2 million or more migrant population. It runs at about 100 million litres per day (mld) (about 10-12 litre/sec) in the dry winter season and about 170 mld in the wet season. But the need is more than 350 mld to meet current demand and this shortfall is met by private vendors drawing on groundwater resources. When all three tunnels are in operation, the additional flow into the Malamchi River will be 510 mld and this is only just expected to keep pace with demand.

“Traditionally, the method of tunnelling has been drill&blast,” explained Gyanendra Lal Shrestha, current President of the NTA. Application of TBMs has long been considered but always avoided. “We worked hard to promote the use of TBMs for the early hydro projects,” said Binaya Shrestha, owner of the Mosh company that has represented The Robbins Company in Nepal for many decades. “At that time, and until very recently, Nepal was considered not ready to apply TBMs and the young geology of the Himalayan mountain range and its foothills were too difficult to use TBMs with success.”

Traditional drill+blast was selected for the Malamchi water supply project
Traditional drill+blast was selected for the Malamchi water supply project

Deformation was considered a particular threat with convergences of up to 12% expected. It was considered that a TBM could manage convergences of up to 9% maximum and so drill+blast has been the adopted method to date.

Assembly of the first TBM in Nepal for Bhari Babai project
Assembly of the first TBM in Nepal for Bhari Babai project

Even for the Malamchi tunnel, TBM excavation was considered too risky and the 27km of tunnel has been excavated by drill+blast working from eight headings – the two portals and in both directions from three intermediate adits.

But for the Bhari Babai project, mechanised excavation was the only way to go. The 12km long tunnel could only be excavated from the two portals. There was possibility of opening intermediate adits along the alignment. For this reason a TBM operation was adopted for the 12km long x 4.8m o.d. (4.2m i.d.) drive working from the downstream portal about 1 hour drive from Nepalgunj.

The Chinese contractor COVEC (China Overseas Engineering Company) is using a Robbins double shield TBM and erecting a hexagonal segmental lining, which is making impressive progress, averaging about 800m/month and recording a best of more than 1,000m/month. Rather than the feared tectonically disturbed metamorphic rocks of the mountains, the TBM is working through relatively benign sedimentary deposits of mudstone and sandstone and is currently 9.5km complete. The pessimistic approach to predictions though has provided the project with a very well prepared, well managed, and well designed approach for the project and has resulted in progress rates of nearly double the anticipated programme average of 400m/month. The 12km long drive is expected to breakthrough in March/April next year, although the last final 2.5km of the drive is predicted to enter into harder and more fractured rock.

Further multi-purpose water diversion projects in Nepal following the Bheri Babai project
Further multi-purpose water diversion projects in Nepal following the Bheri Babai project

The success of the Bhari Babai project has certainly raised the interest once again of using TBMs in Nepal but not in time for the design and specified excavation of the next two tunnels for the Malamchi project. These are designed for drill+blast excavation with a second pass for casting a lining to the walls and applying a fibre shotcrete final lining in the crown, as being applied now in the completed 27km long Malamchi 1 tunnel driven through hard and fracture gneiss, schist and quartize and high volumes of ground water inflows. The long tunnel of Phase 1 is programmed to be completed early in 2019 and tenders for the two tunnels of Phase 2 are expected to be called also in early 2019.

As another significant breakthrough, the next phase for installing 700km of delivery system pipework for the Malamchi water supply project in Kathmandu is to be undertaken using no-dig microtunnelling technology. The first phase of this work for a 700km network within the city’s ring road and through the city centre was installed using open cut trench excavation which caused major disruption and health issues due to the dust generated. The next phase, for the sectors of the city outside the ring road, no-dig microtunnelling has been designed and specified.

Ambitious plans for Kathmandu Metro
Ambitious plans for Kathmandu Metro

Future projects

Also currently in design is a two lane road tunnel of about 2.6km long to the west of Kathmandu. Tenders from one Japanese and five Chinese contractors are currently being evaluated and work is schedule to start next year (2019). There are also several additional water supply/irrigation/hydro multi-purpose diversion projects being developed for rivers across the country, all of which flow south into India. There is also a plan being developed for a rail line running east west across the country and an ambitious vision for a metro system for Kathmandu. There is also plan by China for a railway from China to India linking through Nepal. Amid all, hydro development will remain a high demand industry for the country. It is said that hydro tunnelling will create 50 years of tunnelling work in Nepal. All these projects are a national demand to prepare for indeed.

References

           

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