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
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