Underground Works - # - Sandy McClearn Photography

Photos taken in the underground tunnels, chambers, and works of the Nathpa Jhakri Hydroelectric Project. The Nathpa Jhakri Hydroelectric Project is located on the Satluj (or Sutlej) River (see "F" on the map) in
Northern India. Started in 1993, it was supposed to be completed in 1998. When I started working on this project in February 1999 for Continental Foundation Joint Venture (CFJV), work was nowhere near complete, and the most recent official projection was 2001 (see the sign in the first photo), but I don't think anyone bought it when I was there. When I left in February 2001, work was still going on, and in the end did not finish until sometime in 2004 when the final turbine units were brought online. Some of the delays were man made, but the most serious were caused by mother nature - rock falls and slides, floods, you name it. When I was on vacation in August 2000, a major flood event destroyed 85% of the construction infrastructure, and seriously damaged significant portions of the permanent works. When I left in 2001 - they were still digging out. The photos in this gallery are a selection of the construction photographs that I took documenting various portions of the progress (or lack thereof). The majority are fairly low quality by today's digital standards - 1 megapixel and 2 megapixel images from an Olympus C2000 digital camera, and scanned negative film images taken on a Minolta 7000 with a cheap wide angle zoom lens. It has been a long time since I worked on this project, and as a result I may have some of the technical details incorrect.

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Probably the first tunnel excavated on the project was the Diversion Tunnel (DT), which allowed the flow of the river to detour the dam construction site so that construction could continue. The DT inlet is just east of Point "F" on the map, and on the opposite (right bank) side of the river. The DT ended up being twice as long as originally intended due to a rock fall that occurred at the location of the originally intended inlet (entrance). This photo was taken at the DT inlet during the summer months, with the DT inlet cofferdam visible in the background. The river flows during the summer months were too much for the DT to handle, and would have caused damage to the tunnel lining, so the flows were removed from the tunnel and the summer months were used for maintenance purposes. You can see temporary stairs (made of sand bags) and a temporary ladder that were used to gain access to the tunnel floor.

Another view of the DT inlet, with the same access ladder from the previous image off to the right. To the left you can see the beginning of the concrete lining that was at the tunnel entrance. You can see that a considerable amount of water is leaking past the DT inlet cofferdam, and it was always advisable to have rubber boots (gumboots in the local parlance, and Wellingtons or Wellies in the parlance of my British-extracted supervisor) on hand.

This photo was taken with visible light from the DT inlet, looking in the downstream direction. The Chief Design Engineer is walking further into the tunnel, right under the gate shaft for the DT inlet gate. The gate was lifted by mechanisms stored in a chamber accessible from the road above, although I never saw it used so I am not sure what the point of it was. Perhaps it was supposed to be used for the permanent closure of the tunnel after the dam was constructed, to avoid draining the reservoir, while still allowing the option of diverting the flows during the winter months for dam maintenance. The tunnel at this location was partly lined with concrete, but beyond the gate shaft the native rock was lined with shotcrete, a form of sprayable concrete.

A view further into the DT, about as far as you could go without a flashlight - the lighting here is from spotlights provided to aid the inspection and maintenance of the tunnel. The roof, sides, and floor of the tunnel are lined with shotcrete, and you can see a number of rock bolt heads sticking out of the tunnel roof. The rock in the Himalayas is fairly soft and of low quality, as rock goes, and has a high content of mica which is very soft indeed. This rock does not fare well when put in tension, and so long rock bolts were drilled and grouted into the rock face to provide additional strength and to try and prevent rock falls. You can see the channel worn in the tunnel floor from the water flow.

On the opposite side of the river, and a bit downstream from the dam itself, was the entrance to the Desilting Complex that contained the desilting inlet tunnels, desilting chambers, and Silt Flushing Tunnel (SFT). Normally trucks would be carrying material OUT of the complex to aid the excavation operation, however, this photo was taken after the August 2000 flood and the rock is probably being used to fill in muddy areas to allow the passage of vehicles and equipment. This tunnel is called Adit 2 (an access tunnel), and was part of the infrastructure required to facilitate construction activities.

Further inside Adit 2, this section is supported with steel ribs indicating that the rock here was judged to be unstable. The ribs were made from W shapes (otherwise known as "I" beams), and were placed such that concrete lagging pieces could be placed between the channels on adjacent beams (though this hasn't been done here). As you can see, water was always a problem in the underground works.

The inlet tunnels brought water from the Intakes through to the Desilting Chambers (you can see pictures of the Intakes in the Surface Construction Gallery). One of the jeeps is parked in Inlet Tunnel #3, which has had its invert lined with concrete. The screed form that shaped the concrete would have run on the rails on each side of the tunnel. These rails would later be removed and replaced with new railed mounted right on the concrete invert, to be used by the overt form. A steel bulkhead is visible in the background at the entrance to the tunnel.

This is a rebar installation platform in Inlet Tunnel #1. The tunnel invert concrete has been placed, and the rails have been relocated from the position in the previous photo to the top of the invert concrete. The platform is riding on those rails. As seen here, workers on the various levels of the platform work to install reinforcing steel (rebar) around the circumference of the tunnel overt (crown) prior to the lining of the tunnel with concrete. If you look closely, you can see that one of the workers is actually climbing on the rebar cage between the rebar and the rock wall. My supervisor, the Chief Design Engineer, designed this platform and I was responsible for producing the production drawings that were sent to the steel fabrication shop.

Excavation proceeds in Desilting Chamber #2 in September, 1999. This picture is fairly poor quality, but still gives a good impression of the sheer size of these 500 metre (1/3 mile) long underground chambers. Excavation was carried out in lifts (layers) using conventional drill and blast methodology. A lift was limited in height by the reach of the drilling machines (we used Tamrock Jumbos); the Jumbos would drill a face of rock, and workers would load the holes with explosives. The rock face would be blasted, and excavators would load the broken rock into Hindustan 1025 rock trucks (as seen here). The trucks would remove the rock debris to the dumping area and return for more. When all the rock debris was removed, the Jumbos would return to redrill and reload the face for continued blasting. This process would continue in one lift for the entire 500 metre length of the chamber, before returning to the far end of the chamber and resuming the next lift. This photo was taken looking from the upstream end of the chamber to the downstream end, and the chamber was probably advanced to slightly over 1/2 depth at the time this photo was taken.

Probably the first tunnel excavated on the project was the Diversion Tunnel (DT), which allowed the flow of the river to detour the dam construction site so that construction could continue. The DT inlet is just east of Point "F" on the map, and on the opposite (right bank) side of the river. The DT ended up being twice as long as originally intended due to a rock fall that occurred at the location of the originally intended inlet (entrance). This photo was taken at the DT inlet during the summer months, with the DT inlet cofferdam visible in the background. The river flows during the summer months were too much for the DT to handle, and would have caused damage to the tunnel lining, so the flows were removed from the tunnel and the summer months were used for maintenance purposes. You can see temporary stairs (made of sand bags) and a temporary ladder that were used to gain access to the tunnel floor.