what lies be­neath In­dia’s first un­der­sea rail tun­nel

Work on in­dia’s first un­der­sea rail tun­nel – part of the bul­let train project – has be­gun with a test­ing

Governance Now - - CONTENTS - gee­tan­jali Min­has

The bul­let train, the big-ticket head­line-grab­bing project now firmly un­der way, in­cludes an en­gi­neer­ing mar­vel: the coun­try’s first un­der­sea rail tun­nel. It will come up just north of mum­bai, near Thane creek.

The Na­tional High Speed rail cor­po­ra­tion lim­ited (NHSRC), the im­ple­ment­ing agency for the mum­ba­iahmed­abad high speed rail cor­ri­dor, com­pleted ‘static re­frac­tion test­ing’ for the un­der­sea tun­nel on De­cem­ber 24. The test in­volved fir­ing high-en­ergy sound waves to­wards the seabed from be­low the sur­face of the wa­ter and map­ping the re­sul­tant re­fracted sound waves to de­ter­mine the den­sity of the rock un­der the seabed.

To as­cer­tain soil strength, ex­plo­ration for un­der­sea tun­nel was car­ried out 70 me­tres be­low ground level. as many as 66 bore holes with a gap of 250 me­tres be­tween each pair have been drilled in a stag­gered fash­ion (that is, al­ter­nat­ing di­ag­o­nally) on its align­ment with Ja­panese jackup well equip­ment. Soil strength has turned out to be good and now con­struc­tion will be car­ried out 40-45 me­tres be­low the seabed.

“only a very dense rock can safely sup­port a tun­nel of the present na­ture. The study has now been taken to Tokyo. af­ter its anal­y­sis by Kawasaki ge­o­log­i­cal en­gi­neer­ing co and In­dian geotech­ni­cal Ser­vices the find­ings will be avail­able by sec­ond week of Jan­uary. There­after, Ja­pan In­ter­na­tional con­sor­tium for Trans­porta­tion co. ltd. (JIC) will do the de­sign­ing of the un­der­ground cor­ri­dor,” says up Singh, chief project man­ager, NHSRC.

Seven km out of the 21 km of the twin-track un­der­ground tun­nel will

pass un­der the seabed, man­groves and marsh­lands on ei­ther side of the creek. a stretch of 1.8 km of th­ese seven kilo­me­tres will be con­structed un­der the seabed. NHSRC and RITES, a rail­way min­istry or­gan­i­sa­tion, have also com­pleted the sur­vey of man­groves around the creek us­ing the light de­tec­tion and rang­ing (li­dar) scan­ner, a data recorder and other equip­ment with a 100 megapixel cam­era. This aerial-sur­vey method pro­vides ac­cu­rate data about land con­tours, build­ings and veg­e­ta­tion.

The project cor­ri­dor will be­gin at the un­der­ground sta­tion in the Ban­dra-kurla com­plex (BKC) in mum­bai and then tra­verse 21 km un­der­ground within seven-eight min­utes be­fore emerg­ing above ground near Shil­phata Diva Naka. It will end at the Sabar­mati sta­tion in ahmed­abad.

ac­cord­ing to NHSRC, a 100-mem­ber de­sign team is work­ing on tweak­ing the en­gi­neer­ing of Ja­pan’s Shinkansen tech­nol­ogy to make it work in In­dian con­di­tions.

The prime min­is­ter’s of­fice (Pmo) has sought weekly up­dates on the progress of the project, and en­gi­neers are work­ing round the clock to en­sure that prime min­is­ter Naren­dra modi’s am­bi­tious project is im­ple­mented on time, says Singh.

Plans are be­ing pre­pared by JIC and con­struc­tion is ex­pected to start in the third quar­ter of 2018 with tun­nelling work, ex­e­cu­tion of sta­tions and con­struc­tion of bridges. Three tun­nel-bor­ing ma­chines will be de­ployed. Ven­ti­la­tion shafts will be put up at ev­ery 7.5 km of the tun­nel to give an out­let for fumes emit­ted by the bul­let train. The shafts will also be used for trans­port­ing out de­bris and muck gen­er­ated due to dig­ging which will be re­cy­cled by en­vi­ron­men­tal con­sul­tants.

“With the 21-km tun­nel go­ing un­der­ground, prob­lems of re­lo­ca­tion will not arise, but old build­ings en route will have to be strength­ened,” adds Singh.

mean­while, re­lo­ca­tion of util­i­ties is go­ing on and NHSRC is set­ting up a High Speed rail­way Train­ing In­sti­tute in Vado­dara. The in­sti­tute will pro­vide train­ing for sys­tems and main­te­nance op­er­a­tions to the per­son­nel, be­gin­ning with 4,000 staff mem­bers.

The ₹1,10,000 crore project is ex­pected to be a re­al­ity by au­gust 15, 2022 – the 75th In­de­pen­dence Day. The un­der­ground tun­nel con­struc­tion is es­ti­mated to cost ₹3,500 crore.

The prime min­is­ter’s of­fice (PMO) has sought weekly up­dates on the progress of the project, and en­gi­neers are work­ing round the clock to en­sure that prime min­is­ter Naren­dra Modi’s am­bi­tious project is im­ple­mented on time, says UP Singh, chief project man­ager, NHSRC.

Plan show­ing tun­nel align­ment (Ch. km. -0.234 to ch. km. 21.000)

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