Successful from + 40° to - 40°
Two Sandvik underground drilling rigs are being used to cut the tunnels for the Chutak Hydroelectric Project, underconstruction in the trans-Himalayan mountain ranges of Jammu & Kashmir’s Kargil district in India. The project on Suru River, a tributary of Indus, is being undertaken by the National Hydroelectric Power (NHPC) and has been contracted to the Hindustan Construction Company (HCC) Limited. HCC is using two Sandvik Axera* jumbos in the project that are equipped with Sandvik HLX 5 Rock Drill. The project after completion will provide 44 MW (11 x 4) of electricity to the Kargil district. It is being built at a cost of $80 Million.
Overview of ProjectThe tunneling work involves cutting a 4.8 km long headrace tunnel (HRT) of 5.9m diameter (horseshoe), a 19m diameter and 59 m deep underground surge shaft, a 50m long tailrace tunnel with a diameter of 5.9m (horseshoe), a vertical pressure shaft of 2 x 4m diameter and 37m deep bifurcating into four 2.3m diameter penstocks, two intake tunnels of 4.5m diameter (horseshoe), and three D shape Adits of 6m diameter each. While Adit 1 is 86.62m long, Adit 2 is 240.28m long and Adit 3 is 292.03m long. The underground powerhouse cavern will be 83m long, 15.5m wide and 34.5m high while an underground transformer cavern will be 67m long, 12m wide and 10m high. The barrage is 47.5m length & 15m high above crest level. The rock being encountered in the Chutak project is mainly quartzite.
Difficult TerrainThe mountains in the Kargil region provide a tough challenge for such a hydroelectric project. The biggest challenge is the climate of the location which is a cold desert. The temperature at the project site — at an elevation of 2710m above the mean sea level (MSL)–varies from a high 42 degree Celsius in Peak summer to as low as 40 degrees Celsius below the freezing point in winter. This creates extreme conditions for both the man and the machine. Persons working at the site are found to be troubled by problems like high blood pressure and rapid heart beat and chest pain. The conditions get more difficult during the winter months. The machines too find it difficult to maintain a high level of efficiency under the freezing temperatures. Water lines and air lines freeze during the extreme cold conditions. These machines supplied have special heating systems for hydraulic, diesel and air flushing system for extremely low temperature. However, air flushing system does not solve this problem when the temperature dips to (-) 25 degree Celsius and the air tends to condense and the moisture freezes inside the water line. Also to prevent the fuel from freezing at this temperature, ATF is mixed with diesel in the proportion of 80:20.
Moreover, the site is cut-off by road from the rest of the country for almost six months during the year as the high passes are snowbound from November/December to May/ June. In winter, the only way to reach the site is by flying to Leh and travelling 235 km by road via the 13,780-feet high Fotula (la means mountain pass) to the site location. This demands adequate storage of food, spares, store material and fuel for approximately 6 months during winter. Another unique problem was faced when it was time to take the machines to the site at the beginning of the project. It was found that complete rigs could not be delivered as there was a transportation restriction. The Axera rig weighs 29 tonnes while nothing above 8 tonnes is allowed to be transported in this region due to difficult accessibility and restriction due to capacity of bridges in this region. So the rigs were taken apart completely leaving only the chassis, one in Mumbai and other in Jammu, and then delivered part by part to the site. They were then assembled by the Sandvik engineers on site in six days. Despite such obstacles, the work has continued without a break since its inception in September 2007.