गोष्ट मुंबईची: भाग १३६ | मिठी नदीचे पाणी खाली येऊ नये म्हणून वापरले 'हे' तंत्र!
मुंबई मेट्रो ३ चा सुमारे तीन किलोमीटर्सचा बीकेसी ते धारावी स्थानकापर्यंतचा मार्ग हा मिठी नदीच्या खालून जातो. दुतर्फा जाणारा १.५ किलोमीटर्सचा हा मार्ग भूगर्भात तयार करताना विशेष तंत्रज्ञान वापरण्यात आले. या प्रकल्पामध्ये अनेक महत्त्वाची आव्हाने होती. खणकाम सुरू असताना नदीचे पाणी खालच्या बाजू येण्यापासून रोखणे तसेच भविष्यातही हे पाणी खाली येणार नाही, याची तरतूद करणे, हा मार्ग संपूर्ण सुरक्षित राहील हे पाहणे हेही तेवढेच महत्त्वाचे होते. हे आव्हान मुंबई मेट्रो रेल कॉर्पोरेशनने (एमएमआरसीएल) यशस्वीरित्या पार पाडले आहे. येत्या जानेवारी महिन्यात सिप्झ ते बीकेसी या मेट्रो ३च्या पहिल्या टप्प्यास सुरुवात होणे अपेक्षित आहे.
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00:00 When we came to know that we have to tunnel under the river,
00:03 the type of geology that we are going to encounter,
00:06 and from geology we came to know what type of tunnel boring machine we will need,
00:11 which we call EPBM.
00:13 EPBM means Earth Pressure Balance Machine.
00:16 When the lava rush comes out,
00:18 the soil inside is visible.
00:21 The basalt that we found at the bottom,
00:24 is called composite basalt.
00:26 The BK station is 1.5 km from Dharavi.
00:29 And in 1.5 km,
00:32 the 1 km stretch is below the water body.
00:36 Hello, I am Vinayak Paramghevanwale,
00:53 from LokSapta.com, Ghost Mumbai, Parwadusre.
00:56 In the first episode of Ghost Mumbai,
00:59 after exploring various historical sites,
01:02 we searched for the second episode.
01:04 We will see the modern and ancient Mumbai.
01:08 Now, we can see that I am wearing a headgear,
01:11 which we call a helmet.
01:13 And I am standing at the bottom of the metro station.
01:19 We can see that the metro exit is a tunnel.
01:22 The Bogda is at my back.
01:25 In the previous episode, we went to the MIDC station,
01:31 and we talked to the metro officials.
01:34 Now, we will take a surprising thing,
01:37 and come to this part of the metro station,
01:39 to understand some interesting and different things.
01:42 [Music]
01:52 [Music]
02:20 Now, we are at the BKC metro station.
02:24 And to give us a different information,
02:28 we have with us Suyash Trivedi.
02:30 Hello, sir.
02:31 Hello.
02:32 Welcome to this episode of Ghost Mumbai.
02:34 Suyash ji is the executive director of MMRCL,
02:38 Mumbai Metro Rail Corporation,
02:40 and works as a civil.
02:42 So, Suyash ji, tell us where we are standing right now.
02:46 First of all, thank you for calling me.
02:50 We are at the platform level of the BKC station,
02:54 and we are standing on the track.
02:56 And you can see behind us,
03:00 this is the southern side of the BKC station,
03:04 which goes towards Dharavi.
03:06 And between BKC and Dharavi,
03:08 there is a big border body,
03:10 which we call the Meethi River.
03:12 So, this tunnel has gone from the Meethi River.
03:14 Friends, this is a very important thing.
03:16 I had said in the introduction that
03:18 we will understand the wonder of Mumbai's ocean
03:21 and a different thing in this section.
03:24 So, as sir said,
03:26 we are standing on one side of the BKC station,
03:28 and the river that we can see going towards the back,
03:31 is going towards Dharavi.
03:33 And the most important challenge or obstacle
03:36 in front of MMRCL,
03:38 is that the Meethi River is flowing from the top,
03:40 and the river bank is to be built from the bottom.
03:43 Sir, we will understand this from the beginning,
03:45 that how did MMRCL do this work?
03:49 Sir, tell us,
03:51 it is very difficult,
03:52 there is water on the top,
03:53 a river is flowing,
03:54 and we have to dig a tunnel on the bottom.
03:57 So, you have to do a pre-preparation,
03:59 a plan, a homework.
04:01 So, what was the homework done by MMRCL?
04:04 You have understood the point,
04:06 that if you have to give something well in the end,
04:09 then its planning is very important.
04:11 And the huge technical work,
04:14 the planning is very important in that.
04:17 When we came to know that we have to do tunneling under the river,
04:20 we emphasized that
04:22 the type of geology you are going to encounter,
04:26 you should already know that geology.
04:29 And to know the geology,
04:31 you have to do a detailed soil investigation,
04:33 geotechnical investigation.
04:35 So, we along the Meethi River,
04:38 and we found out the geology from that,
04:40 and from the geology,
04:41 we came to know that
04:42 what type of tunnel boring machine we will need.
04:45 So, all those factors were decided,
04:47 on that, you did a detailed geological investigation.
04:52 So, in this geological investigation,
04:54 we have heard that
04:55 you have got two types of layers.
04:58 The first one, the upper slush,
05:00 that was under any river,
05:03 the common river,
05:05 and later,
05:06 you have got basalt in two layers below that.
05:09 Will you tell us something about that?
05:11 So, during the geological investigation,
05:14 we came to know that
05:15 the upper slush of the river bed,
05:17 is below the slush,
05:19 which is a fragmented rock,
05:21 brachiated basalt.
05:24 And below that,
05:25 the upper basalt,
05:28 is a little fragmented,
05:30 in technical language,
05:31 it is called grade 4 and grade 5 basalt,
05:34 which means loose.
05:36 And below that, the grade 2 and grade 3,
05:39 the competent rock,
05:41 that was also basalt.
05:42 So, this we came to know after our investigation.
05:45 And because we were below the river body,
05:47 so keeping all those factors in mind,
05:49 we designed the EPBM,
05:51 Tunneling Boring Machine,
05:54 so that,
05:55 we can handle all the technological challenges,
06:00 that we are going to encounter.
06:03 Friends, I will explain in a little while,
06:06 Sir told us that,
06:07 the basalt on the upper side,
06:09 is called brachia.
06:10 Brachia is a type of rock or rock,
06:13 when lava rush comes out of it,
06:16 the soil inside it,
06:18 is visible in it.
06:19 The layer of it,
06:20 is called brachia.
06:22 And the basalt that we found below that,
06:25 Sir told us,
06:26 is called composite basalt.
06:28 It means,
06:29 its density is very high.
06:31 And the best percentage of basalt,
06:33 was found there.
06:35 And so,
06:36 the decision taken by MMRCL,
06:38 that the composite basalt,
06:40 that is found below,
06:41 the tunneling is done in it.
06:44 But I feel Sir,
06:45 that still there was a lot of,
06:47 confusion.
06:48 The reason for that is,
06:49 what if suddenly water comes,
06:51 what will we do?
06:52 Or,
06:53 the pressure suddenly increased,
06:54 because pressure is not in your control,
06:56 when you go down at that time.
06:58 So, how did you handle that?
07:00 Means,
07:01 did you do something different in the machine,
07:03 in the nail boring machine,
07:04 that the pressure was handled?
07:06 Yes.
07:07 As I told you,
07:08 that we have,
07:09 for this particular stretch,
07:11 designed a particular type of TVM machine,
07:14 which we call EPBM.
07:16 EPBM means,
07:17 Earth Pressure Balance Machine.
07:19 So, what is the concept of this?
07:21 Basically,
07:22 when you are doing the tunneling,
07:25 then in front of you,
07:27 there is a natural pressure of the soil,
07:29 and when you are doing the tunneling,
07:31 then what you have to do is,
07:33 the natural balance,
07:34 the natural pressure,
07:36 you extract the mug in such a controlled way,
07:39 that the natural pressure,
07:41 which is your balance,
07:43 so what happens with this,
07:45 that there is no settlement above,
07:47 and your mug extraction,
07:48 remains controlled.
07:50 So, by controlling the mug extraction,
07:52 you get to know the nature of the mug.
07:55 Suppose, you are moving forward,
07:57 and you have presumed some expected nature of the mug,
08:01 that it will be like this.
08:03 But all of a sudden,
08:04 you come to know that,
08:05 no, the quantity of water is increasing,
08:07 the quantity of mud is increasing,
08:09 so that is an alarm for you.
08:11 And as soon as you get that alarm,
08:13 then you should know,
08:14 what should be your next course of action.
08:17 So, we designed this special type of machine.
08:20 There is one more interesting feature in this machine,
08:23 that suppose,
08:24 you get some unusual nature of mug,
08:27 so in this machine,
08:28 forward probing,
08:29 means,
08:30 to know what is ahead of you,
08:32 there is a system of forward probing.
08:34 So, what you can do is,
08:36 you can know up to 15 meters ahead,
08:38 that what type of mug is coming,
08:41 is it an aquifer,
08:44 means,
08:45 an underground pond of water,
08:47 or something like that.
08:49 So, you get to know what is going to come ahead,
08:51 so that you can know 15 meters ahead.
08:55 The system was in this machine.
08:57 Yes.
08:58 So, the first line of defence is,
09:00 you should analyse the mug.
09:02 If the mug is in the expected line,
09:03 then there is nothing to do.
09:04 But if the mug is different from the expected line,
09:07 then you have to do forward probing,
09:09 to see if there is anything unexpected ahead.
09:11 So,
09:12 was there anything unexpected here or not?
09:15 As I told you,
09:17 we did a very detailed geotechnical investigation.
09:21 And,
09:22 we knew what is expected from each of the stages.
09:26 So, fortunately,
09:27 we got the geology of the type we expected.
09:31 We did not encounter anything unexpected.
09:33 So, your homework was good.
09:34 But we were ready.
09:35 If something would have happened,
09:36 we would have been ready for everything.
09:37 But your homework was good.
09:38 Yes.
09:39 So, nothing happened because of this.
09:40 Sure.
09:41 Okay.
09:42 So, sir,
09:43 this tunnel,
09:44 which we are seeing behind,
09:45 is starting from here.
09:46 It is a stretch of about 1.5 km.
09:47 And it goes from here to here.
09:49 Secondly,
09:50 we tried to find out something before coming here.
09:53 We found out that the channel of Mithi River is a bit small.
09:58 But the water body,
10:00 which we call the water body,
10:02 is very big.
10:04 And our line has gone in curvature.
10:07 So, please tell us about that.
10:09 Sure.
10:10 So,
10:11 you will see that the next station behind us is Dharavi.
10:14 And this station is BKC.
10:16 So, from Dharavi to BKC station is 1.5 km.
10:21 And in 1.5 km,
10:23 the stretch of about 1 km is below the water body.
10:28 Okay.
10:29 So, the active channel of Mithi River is around 250 m.
10:33 But when high tide comes,
10:35 this entire 1 km is basically inundated with water.
10:39 Yes.
10:40 So, half a kilometer going and half a kilometer coming.
10:43 So, up and down line.
10:44 So, total 3 km is the stretch of this tunnel,
10:47 which goes down below the Mithi River.
10:50 Yes.
10:51 So, 1.5 km east side.
10:53 Okay.
10:54 So, total distance is 3 km.
10:56 But Mithi River,
10:57 up and down line both sides,
10:58 if you calculate,
10:59 that's 2 m below water body.
11:02 Okay.
11:03 And we have also heard that
11:05 you worked with a tunnel boring machine.
11:08 The good thing is that your homework was good,
11:10 so nothing happened.
11:11 Yes.
11:12 But we also predict,
11:14 when we do big projects,
11:16 that if something goes wrong,
11:18 what will happen to it.
11:19 So, we have found that
11:21 in the construction of this tunnel,
11:23 you have also devised a method
11:26 that if water comes,
11:29 then it can inflate and
11:31 can be saved.
11:33 And water will not come inside.
11:35 So, you tell us about that too.
11:37 So, when we do tunneling with TVM,
11:39 as we excavate with TVM,
11:41 we make a lining in the back.
11:45 We make a lining of concrete,
11:46 free cast concrete segments.
11:49 Because this whole ring is not together,
11:52 it is in part-part segments.
11:54 So, it makes 6 segments and
11:55 makes one round.
11:56 Okay.
11:57 So, there are joints in between.
11:59 So, we have to treat the joints everywhere.
12:03 Everywhere you have to put gaskets in the joints.
12:07 Gaskets have to be put in every joint.
12:10 Here, because it is below the water body,
12:13 we have put double precautions.
12:15 First, we have kept the width of the gasket more.
12:19 We have kept the width more.
12:21 And we have designed special type of gasket.
12:24 We call them mushroom type gaskets.
12:26 Okay.
12:27 And I think,
12:28 this type of gasket has been used for the first time in the world.
12:30 Okay.
12:31 So, that EPDM,
12:33 the material is called EPDM.
12:35 We have used the gasket of EPDM.
12:37 And the second layer of defense that we have put in it,
12:40 along with this,
12:41 we have also put a hydrophilic gasket.
12:44 Okay.
12:45 The character of the hydrophilic gasket is that
12:47 as soon as it comes in contact with water,
12:49 it swells.
12:50 Okay.
12:51 So, as soon as it comes in contact with moisture and water,
12:53 that will give you extra defense layer.
12:56 So, automatically it will get swelled.
12:58 So, it will stop the water.
12:59 Okay.
13:00 Okay.
13:01 Friends, we have understood a very important thing today.
13:04 The first thing in all this is that
13:06 the metro line that is starting from Sips to Kulabai,
13:12 the first part of it,
13:13 may be in the next month,
13:15 that is in December,
13:16 or
13:17 at the beginning of the new year,
13:18 as a gift to the people of Mumbai,
13:20 this part will start here.
13:22 And the first metro line,
13:24 will run from Sips to BKC for the people of Mumbai.
13:27 The reason we came here today was
13:30 to understand the work that has been done here.
13:32 To understand what has been done.
13:34 And the most important part,
13:36 which is surprising for the people of Mumbai,
13:38 is the slope that goes under the Methi River.
13:41 How was it done?
13:42 How was it done?
13:43 And maybe there is a small fear in our minds,
13:46 that what to do if water comes suddenly.
13:48 So, the danger of that too,
13:50 no such incident,
13:52 no accident will happen,
13:53 the danger of that too,
13:54 has been done by the MMRCL.
13:56 So, friends,
13:57 the slope that goes in the direction of Dharavi,
13:59 which goes under the Methi River,
14:01 we came there and understood
14:03 that the slope that goes under the Methi River,
14:05 is of great importance.
14:07 How was it done?
14:09 And the safety policy in this,
14:11 we will see how well it has been done by the MMRCL.
14:15 Now, we will stop here for today.
14:17 In the previous parts,
14:19 we saw how well the work of the MMRCL has been done.
14:23 We have understood the many different things
14:25 that are there in its context.
14:27 So, keep watching Lok Satta Live YouTube channel.
14:30 And don't just watch,
14:32 but try to share it with your friends.
14:34 Don't forget.
14:36 www.mrclinic.com