SPOTLIGHT AGENCIES
Written By Ravi_D - 2 March, 2010
Bangalore Namma Metro Citizen Reports BMRC Tracking underground Transportation public transport Metro Rail Phase1
Just noticed the numbers for land acquisition in the Feb Newsletter.
UG NS Stretch - Proposed: 14, Possession Taken: 8, Demolished: 7
UG EW Stretch - Proposed: 129, Possession Taken:0 (!), Demolished: 0 (!).
Read in DH today that the UG-EW Stretch is awarded.
If the acquisition numbers are correct, brace yourself. Contractors will have a perfect excuse for all further delays - The stretch took an additional year and a half.... because.... we couldn't get our TBM underground!
Vasanth - 4 August, 2010 - 11:24
Ravi_D - 2 March, 2010 - 08:46
UG Section pre-qualification tender document is silent about TBM. This 2007 July DH Article implies BMRCL may itself be importing TBMs. Latest BMRC Contractor's List does not specify who is building them. Any ideas?
Have they already been ordered and sitting ready for use? These monsters could have significant lead time, especially if custom built and shipped ocean freight from Europe.
srinidhi - 2 March, 2010 - 09:28
As I could understand, these TBM's are built for specific needs...for example Delhi had mostly alluvial soil and it was relatively easy drilling there..
"Since the bored tunnel construction for Delhi Metro involves tunnelling through both hard quartzite and soft ground, two types of tunnel boring machines (TBMs) are being used. Rock TBM is being used for quartzite while Earth Pressure Balance Machine(EPBM's) is being used for soft soil. "
In case of Delhi Metro two EPBMs obtained are second hand i.e. they had worked on metros of Bangkok and Taiwan. Before being put into use at Delhi these machines were completely refurbished or overhauled. The dual mode machine for rocks is brand new specially manufactured by Herrencht of Germany and costs about Rs 30 crore. The main difference between the two type of machines is Cutter Head design."
However as Metro ppl are saying..they are getting rock structures all thru their path in blr..hence I think the consortium which has been selected should decide and lay the specifications for the TBM's needed!
This may be a looong prozess!!!
Ravi_D - 3 March, 2010 - 04:22
...I'm beginning to suspect that the UG sections are planned to be done by cut & cover method, which will create havoc for the public
@Naveen: Interesting Observation there.
The pre-tender qualification document says NATM method would be used. But the interesting part is in Section 4.3 of the document.
"Anticipated construction method ... is twin bored tunnels...while stations utilize "cut & cover". However, it may be necessary that some sections of bored tunnel construction be changed to "cut & cover" or other tunneling methods utilized due to site conditions..."
Further section 4.3.1 talks of use of EPBMs for strata of soil/weathered rock.
"Cutter wheels shall be capable of cutting thru' stiff to hard rocky soils but not necessarily thru' hard sound rock. .... In areas where hard rock is encountered.. Either an appropriate Shield TBM.... or a mining method such as NATM may be required. At some locations, cut & cover method may be adopted."
I read the above as TBMs for most of the length, and cut & cover for the hard rocky areas. Doubt they'll take the trouble of changing machines every few hundred meters, depending on the strata they encounter. Certainly like to see a plan of the tunnels showing where specific methods are expected to be adopted. If they have awarded the tender (for E-W section at least), bidders should have had this information to be able to Quote!
Naveen - 2 March, 2010 - 11:00
Judging by the silence about TBMs & also news reports about whole roads being taken up for construction (eg. Vidhana Veedhi), I'm beginning to suspect that the UG sections are planned to be done by cut & cover method, which will create havoc for the public.
Why is it that there have been no press announcements about TBM machine imports ? They should have been here by now. And a delay has been announced - is this coincidence ?
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