Good afternoon. Afternoon. Uh, it's, uh
I'm Mike Duncan. And I'm here, uh,
to welcome all of you to the eighth annual Schnabel
Engineering Lecture. And those as many of you know
, uh, the Schnabel lectures are an annual feature
highlight of the fall semester. And, uh,
the person that we have to thank for that is
Alan Cadden. Uh, he These were his ideas
. And he is, uh, spearheaded this every
year, and we're thankful for that involvement in our
program. Allen is the the director of strategic development
for Schnabel Engineering and a great supporter of our program
. Uh, so let's thank Allen for his supporting
this lecture every year and welcome him to the podium
. What do you think you're doing? Thank you
, Dr Duncan. It's a pleasure to be back
here. Yeah, every year. You know,
I love coming down here a couple of times a
year, and if I can figure out how to
do it, I'm gonna convince all of my kids
that they have to come here. But I'm just
hoping they get through high school right now. Good
afternoon, everybody. And I appreciate you coming out
this afternoon. We're happy to bring this lecture.
This eighth lectures to Virginia Tech again. And I
first want to thank Dr Phil's and Mr Simpkins for
organizing all this for us. We do appreciate all
your help and everything with this. Um, I'm
sure many of you weren't really clear about what engineers
do when you were going through high school. At
least I know I wasn't. Unfortunately, we don't
have C for engineers. So we like to bring
this lecture to you and hope that by bringing these
guests here, and they can explain how they spent
their career working on some pretty impressive projects and impressive
engineering challenges, you'll help understand our industry and in
the many opportunities that engineering brings. And as you
understand this a little further going through your your education
and through lectures like this, uh, we hope
you're a little better prepared to share with others and
help them understand the thrill of engineering in this profession
. One of these days, we'll have our own
TV show, but not right now. So thanks
for joining us. If I could just take a
moment and introduce you to Snoble Engineering. Schnabel's an
employee owned company. So we're 100% employee owned.
Everybody has a little piece of the company, and
it's a great environment to work. So we specialize
in finding solutions for our clients where they're dealing with
the Earth, and that involves a wide array of
geotechnical geo structural dams, tunnel engineering and all those
related sciences that go along with it. So it's
a pretty exciting area to work in. I'm also
proud to say that for the, um, 11th
year in a row, we've been recognized by C
magazine is one of the best places to work,
so it can't be all bad. Uh, we
have 19 offices located throughout the United States. From
these locations. We work on projects around the world
providing a full range of services from design through construction
. Challenges presented by these projects probably cover nearly every
aspect of the, uh, every aspect of your
professors are describing to you, and maybe a few
more that they won't have time to address in the
classroom. So it's pretty interesting. Um, so
, without further do want to kick off the eighth
installment of this noble engineering lecture, the Schnabel lecture
strives to bring you representatives of the civil engineering design
and construction community who has significantly impacted the advancement of
our practice. These industry experts come to share experiences
and insights gained throughout their career and provide a little
of their insight as to what you may be seeing
as you begin your career. There's absolutely no way
we can tell what you're gonna see as you approach
the end of your career, because that's entirely up
to you. Mhm. So our eighth lecturer,
compliments of previous speakers, each of whom have focused
on a unique piece of the geotechnical profession and the
growth of our industry today, we're proud to bring
you the 2013 Schnabel engineering lecturer Dr Ed Ed recording
. Dr. Cording is professor emeritus of civil engineering
, civil and environmental engineering at the University of Illinois
at Urbana Champagne. His career focus has been on
rock mechanics, soul structure, interaction and underground construction
. The field has the field has been his laboratory
, beginning in the sixties with large deep caverns and
weak rock in Nevada and in the seventies, with
subway tunnels, braced excavation and rock caverns on the
Washington metro, continuing on with deep tunnels and squeezing
ground in the mhm Utah mountains and urban tunneling and
soft consolidating Chicago clay. So you've seen a little
bit of everything underground? Uh, Dr Corday has
consulted on underground projects from subways, rail, wastewater
, highways, water supply mines, liquefied gas,
high energy physics, nuclear waste and hydro electric projects
. So we are building all kinds of things underground
and some great challenges presented to us. From 91
to 97 he was appointed by President Bush to the
U. S. Nuclear Waste Technical Review Board for
Site Investigation of Yucca Mountain. He's consulted on underground
transit tunnel projects throughout the United States, including nearly
all of the recent tunnel projects in New York City
that you've been hearing about. Currently he serves as
a tunnel advisory panel for the Los Angeles Metro and
supports Seattle Tunnel Partners for the Alaskan Way Viaduct,
which I believe is included in this presentation. It
has to be the largest soft ground tunnel ever constructed
. Correct. Looking forward to that about that one
. His honors and numerous, including election to the
National Academy of Engineering, the A S C.
Martin Cap Award, the Harry Schnabel Junior Award for
Career Excellence in Earth Retaining structure. That's the other
snoble. Uh, the Moles Nonmember Award, the
Beavers Engineer Award for outstanding achievement in heavy engineering,
heavy engineering construction. So he's got the left and
the right coast covered and numerous invited lectures. So
today is gonna describe the revolutions in tunneling technology that
allow us to do just about anything underground. So
please join me and welcome Dr Headquarters. Thank you
. Thank you, Alan. And thank you.
Virginia Tech and Mike Duncan. Professor Duncan and others
here, too, for having me on campus.
I've enjoyed the time I've been able to talk with
faculty and students today. It's been one after the
other, but it's the first time I've been on
your campus, and I'm really enjoying and appreciate the
opportunity to be here and talk with you and many
of you. I am honored to receive this invitation
to give the lecture for the the Eighth Schnabel Engineering
Award and special to me because I knew, uh
and no have known both, uh, the novel's
Harry Schnabel and Jim Schnabel or Brothers Jim forming Schnabel
Engineering, which you've been hearing about, and and
Harry, the Schnabel Foundation Company, both very successful
in their in their own ways over the years and
around the country. So they were personal friends of
mine, and and so that makes this also very
special. I want to talk today about, uh
, the revolution and tunneling. And, uh,
I think that, you know, we we talk
about the things that are happening to us. And
you look at what we were doing 15 years ago
in communicating and now working with our online communications with
the web and all the the ways that we have
to communicate that we didn't have before. So we're
all have been experiencing revolutions, revolutions in our the
way we live. And, uh, but this
revolution is partly due to the things that we can
do today with, um with downloading information and distributing
it electronic data collection, which is happening everywhere.
But it also has to do with the behavior of
the ground and how we understand the behavior of the
ground. So I'm gonna be talking today about those
some of those items I wanted to talk about that
revolution, and one of the things that that Alan
Kay gave us was the title to this lecture,
and he basically said, Let's put in. He
gave him the the abstract and he gave the title
and I started looking. I thought, well,
that that's really good to say We've come a long
way and that means two things. It means that
we're not. Maybe we're not necessarily doing things that
we're doing new things, but it also means that
we we are building on what's been done before.
And that's one of the things I want to to
emphasize as we go through this. It's not just
that we're using the latest technology, it's that we're
building on a background of information and observations and experience
and precedent in civil engineering. So I'm gonna go
back in time and look at a few of those
cases and this is not a history lesson. It's
our precedent as engineers, as engineers we have to
work with. We have to understand what is done
is being done in the past. We may go
beyond that. We need to know when we're going
beyond previous experience, so that's one of the things
that will be focusing on. And there has been
a revolution that allows us to tunnel deep beneath waterways
without the inflow of soil or water, and it
also allows us to tunnel at shallow depths below urban
structures without damage. And that's what I wanted to
talk to you about today. But I want to
go back about 100. Uh, it's over 190
years now to the first shield. We call them
shields or cans that are used to advance the tunnel
and in which the support is installed. So I
want to talk about the first shield tunnel in London
. In the 18 18, there was a patent
application for a circular tunnel shield, and it was
made by Mark Eisenberg is, um, barred Brunel
, and he described his objective as to open the
ground in such a manner that no more Earth shall
be displaced then is to be filled by the shell
or body of the tunnel. And that's what we've
been trying to do for 190 years. And as
we go through the lecture, let's look at where
we've we've gotten. I've given lectures in the past
that says, Well, we're not quite there.
First Shield Under Under a river. He made sounding
Zargar boring, designed the tunnel, obtained financing.
He designed and built a 40 ft wide Uhh shield
40 ft wide tunnel. He directed the construction,
had five floodings that he recovered from. He rebuilt
the shield under the river and refinance the project and
he was knighted by Queen Victoria in 18 41.
Now we talk about substantial completion and engineering projects.
That, to me, was substantial completion to be
knighted by the Queen. The tunnel is in service
today, still in service today on the London Underground
. But the objective was not achieved by Brunel and
he had those loss of ground into the river.
And you can see over here we've got This is
the bottom of the river and this is the material
they've been dropping in here to fill the void the
inflow that occurred into the front of their tunnel shield
. Here's the tunnel, and this material has flowed
in up to here and that maybe Burnell or his
son is embargoed Kingdom Brunel, who went on to
build many of the railways and bridges in in the
United Kingdom. And so that might be them in
the boat. But they what a project. And
it wasn't just doing technical things that was making the
whole entire project work. Mhm. And so I
want to talk just briefly about the deep beneath waterways
part of this, and go to New York City
. For almost 50 years, there have been no
tunnels under the river except for one case up here
on 63rd Street, and they put in in the
sixties. They put in a immersed tube, just
dropping the floating the tubes in, dropping them down
into the bottom, the river but no tunnels underneath
the river. The last tunnel under the river was
the Lincoln Tunnel in the 19 fifties, the third
tube of the Lincoln Tunnel Highway Vehicular highway tunnel.
And that was the last tunnel for the larger,
I think, almost the last one under the river
, except for some very recent ones that have been
going in, um, for almost 50 years,
why it was that perhaps we didn't need it.
They didn't have the funding. But there's another reason
. It's very basic. Here was the tunnel.
In 1910, they came. The Pennsylvania Railroad wanted
a terminal in New York, along with the New
York Central Railroad. They wanted to get into New
York and not barge or fairy fairy. Their trains
across the river from New Jersey, so they put
a tunnel under the river and, uh, they
kept it as shallow as they could. But they're
still down pretty great depths. And in order to
advance that tunnel, are using compressed air air pressure
in the front of the tunnel to advance the tunnel
. And they're working through from the New Jersey side
on the left to the New York City Manhattan Island
on the right, he was compressed air. It
was high. Has the pressures or hazardous work rules
were not in place? It was unsafe. The
the sand hogs were getting the bends. It was
extremely dangerous. They had one project, I think
, by the in the 19 fifties, where they
for the entire Project Tunnel project, was completed with
no fatalities. That was the history of tunneling bold
, big, dangerous and something that, with our
understanding of the of compressed air effects on the body
, we can no longer do these sorts of tunnels
. If you're going to run a tunnel down at
this depth with compressed air, the workers will probably
work for two hours. You can't have four shifts
of workmen working in the tunnel and so no tunnels
. And now we have in 2000 and eight design
. It isn't built yet. It's got stalled for
reasons that it was in New Jersey. Decided we
don't want the tunnel right now. Uh, and
if the Trans Hudson Express we're going deeper and we're
not using compressed air, as during the tunneling and
why Why is that? Because we have now what's
called the pressurized face systems, either slurry machines or
earth pressure balanced machines. The earth pressure balances what
we're primarily using and what is it that makes it
work? It's the fact that at the front of
this as the muck or the excavated soil, the
spoil comes into the front of the tunnel. Uh
, the front of the face through the cutter head
. It's for it forms in this chamber and its
conditioned with foam in order to make it a viscous
fluid that will provide a positive pressure to the face
. And then uh huh um, we have the
skate the screw, removing that condition of material and
providing the back pressure as you operate the screw with
respect to the events of the machine that keeps the
pressure on the front of the tunnel and then in
the back. The lining is tunnel lining is a
segmental lining erected in the tail of the shield.
And then ground is injected through the tail as the
shield is shoved to fill that gap. And so
this is one of the reasons that we are.
This is the reason that we are able to tunnel
deep under rivers around the world and its rivers seaways
. We have the capability to tunnel at pressures that
generally are less than about eight bars, which would
be, um, 120 c. And that would
be about, uh, 260 70 ft of water
. So we're able to go deep. You don't
normally operate at those those high values, but we
can do that. The other revolution is we can
do it at shallow depths. And let's look at
that. And this is what we're doing in the
Alaskan way Viaduct Replacement tunnel to replace the viaduct in
in Seattle. That has to come down, and
we want to be able to take it down before
we have a major earthquake in Seattle that would cause
it to be taken down. Uh, The tunnel
is 57 a half feet in diameter, and we
wouldn't even consider driving a tunnel under downtown Seattle,
uh, without having the technology that's really been continuing
to develop over the last 30 years, but particularly
over the last 10 years, the capabilities that we
have here's the Here's the cutter head for the tunnel
Boring machine. It's Bertha and, uh, the
name. And so I guess you could call it
Big Bertha. 57 a half feet diameter is the
world's largest shield tunnel. Um, and here's some
of the buildings were going under the first. Some
of the first buildings that we tunnel under these are
older buildings. 19 turn of the century 1900 buildings
in Pioneer Square in downtown Seattle, and that's the
machine next to it ahead. And, of course
, that head will be down about 100 ft 80
ft below that. Those buildings. This is the
launch box where they're starting the construction. We're looking
south of the machine is going to come this way
. The head is in place here, and here
are the tail. Here's the shield with the front
section of the shield and what we would call the
tail section of the tunnel shield their articulated, and
, uh, we'll show you a few more details
on that. We can look down and we can
see the joint Venture Grottoes and tutor Perini that I'm
working with and and then you can see the Cutters
. And then we also have the chamber behind.
The cutter head is right in that zone that I
have there in red, and you can see that
the buck comes into the in between these these spokes
and comes into the cutter head, and it's held
in there under pressure. That's the key to the
operation of these machines. Uh huh. And now
we're kind of looking at installing this the equipment in
the back of the cutter head and behind the front
section of the shield. And so here we have
a series of shove jacks that push the machine forward
. We have a airlocks in here to get into
the front. If you have to get into the
front of that head under when it's under pressure,
there's a lot of pressure outside. You can evacuate
some of that and go under compressed air, so
you're back into the compressed air, but you end
up with very short work periods if you're working at
high pressures. But those you know, you look
at that and say, I don't know, how
can anybody get in there? But that's large enough
to get a person in their their men working down
here. You can see them right here. And
so the scale of this is immense. And as
we take a closer look here, this that central
zone is the central ring is where the screw conveyor
will actually be attached to. The screwed could have
air here, uh, is outside in the ground
. It would be taken down and attached at that
location. This is the tail can, that's it's
going to be lifted in place. And then we
have the concrete segments there, almost approximately 2 ft
thick. And there's gaskets around them, and they
put together, as in a ring in the back
of that tail can as the shield moves forward.
Uh, the after the end of the shove or
the advance of about 6 ft that will then put
that ring in, and then the shield will push
off on those segments again. And that becomes the
initial support for the ground, and it's also the
permanent supporters used on almost all of our projects transit
projects, for example. It's the final lining that's
installed as the tunnel advances. Here's the Gantry Crane
. It's brought in a special company for the lifts
. Its 1000 tons, um, the left,
some of the highest, largest lifts in the country
. But for example, if you're putting in a
a containment structure structure for the nuclear power plant,
I think some of those lists can go to 2000
tons. So they brought in a special company to
do that to make the lifts. And, uh
, here's the the section of the back of the
shield that erects the concrete segments. They have to
take them in and then turn them up and form
that that ring and that's that's the ring Erector.
But what I want to look at right now is
our test section. We have 1000 ft to go
along the side here. We're actually working in a
box between secret piles or tangent piles, and they're
using this zone next to the Alaskan Way Viaduct as
a test section, and we're running the test to
evaluate and to develop the tunneling procedure and to evaluate
ground movements. And so that's That's the effort that's
going on right now. Contractor laid this thing out
. He extended the contract limits in order to the
extended them in order for the contractor that you do
this 1000 ft section. He that was his proposal
when he came in and did the job planned or
proposed for the job. And here's the machine in
place, ready to advance and we have the We're
going along the viaduct. We drive under the viaduct
and then under downtown Seattle under the Alaskan Way Viaduct
there. And here's we are under the viaduct and
then beneath these buildings. These are the critical parts
of the project because things are pretty shallow here,
relatively shallow, we're deep, but it's relatively shallow
with the diameter because of the diameter of the machine
. Uh huh, and just kind of looking at
some of the structures were going under. That's just
the start of the tunneling in clay's glacial materials clays
, sands and the thing that's happening, this is
inside the machine, having a room inside a tunnel
. Boring machine is kind of a special thing because
it's just such a big machine. You can do
that, but it's an electronic tronic read out.
This is the operator and they're getting set up and
he's operating the machine from this console. And this
is what we really need to couple with the measurement
of the ground movement and the water pressures. And
we can integrate that data and we can read it
out and and it can be distributed electronically. So
we have you can. You can download that and
I can. We can look at the progress of
the machine, and so the Jew techs are going
to need to be working very closely with the machine
people and understanding how the machine operates. That's what
we need to understand about. The project is not
just JIA Tex techniques, but how does the machine
affect the ground behavior or vice versa. That's not
different than what we've done in the past is that
we have to look at construction projects and figure out
what it is isn't about the construction that's affecting our
project, and so but in this case we can't
see the ground. We have to rely on the
readout and certainly the operator has to control and monitor
the machine. But we need to We have to
observe the ground behavior we can't stand and look at
the soil coming into the tunnel. We can see
the muck coming out, but we have to look
at the the instrumentation to figure out how the ground
is behaving or what the movements are, what the
pore pressures are, whether it's coming into the tunnel
. So we have come a long way, and
, uh, but I want to go back in
time a bit and and talk about our precedents linking
the construction events with ground behavior. And I want
to go to three projects very briefly. 1939 1941
. The work. There's a G and peck we're
doing in Chicago, and these were pioneering observations.
Um, and as I said before, we're building
on that experience and how the ground behave. So
even though it was different construction, it's valuable to
us as engineers to understand those what was done on
those projects. And as we move forward with our
new, uh, projects and different construction techniques,
here we are in the Chicago subway. They did
what they called squeeze tests. Uh, in an
open face, they could see the clay that's the
clay being cut, their and their opening it up
in sections. And the primary objective here was to
relate what was happening in the tunnel to the ground
settlements at the surface. Here's some very large settlements
in this case, uh, but but that it
was kind of a situation that, yes, we
knew that tunneling cost settlement, but we haven't really
evaluated. And that's what Herzog he did. And
Peck was, uh, had come out of his
, got his PhD and studied at Harvard. I
was studying at Harvard with Castle Grande, and he
served us in the field to run. The laboratory
, which was really making these field observations, is
doing some of the first series of extensive unconfined compression
tests and water contents sampling. It was really the
start of I think Inpex experience and and perhaps really
focused in Trezza G experience on the observation method.
So here's Here was the three things that are going
on. This is from one of his actual summaries
, and instead of electronically, that's on blueprints and
but they were putting it all on here on the
other part of this diagram. It's not in this
picture. They had had the water content and or
the soil strength. Um, they had other displacements
that were happening, uh, at different parts.
They had it all on one blueprint, and you
could integrate. They were integrating the construction and the
ground movement. And there we have. For example
, the top is the surface settlement on the street
. And then down in here, they're showing where
the headings multiple headings were at different times and then
when the instruments were being installed and then what the
displacements were. And so here's the displacement. Across
the side of three, it's an eighth of an
inch. So they were trying to evaluate them,
and they were evaluating these items. They're looking at
the construction, taking notes, carefully, observing the
obstruction and construction. They were looking at the ground
loss, or how much is coming into the tunnel
and relating that ground loss that volume to the surface
settlement. And that's what we're still doing. And
we're doing that on the Alaskan Way viaduct. But
we aren't using blueprints in Washington, D. C
. In 1972 I worked on this with a number
of grad students. The University of Illinois, Uh
, and we were looking at for the three D
pattern of ground movements around this open face tunnel shield
. And so the surface settlement was extremely large.
Six inches, and we're monitoring displacements as the tunnel
went underneath, in this case, Lafayette Square,
in front of the White House, and the settlements
were 13 inches, Uh, on an X Town
extra sound are located just a few feet above the
tunnel, 13 inches of settlement, and it resulted
in the surface settlement of six inches. And we
had in kilometers ahead of the face first servo in
kilometers that have ever been developed. And they gave
us the precision so that we could measure settlements in
the 10th of an inch or less range. And
so we were able to see that we were getting
displacement into the face of a quarter of an inch
. That was not the cause, which is very
often can be the cause of the ground loss.
But what was the cause? The cause. That's
a rhetorical question. Let's go on here. Um
, we measured that displacement, and then the source
was over the shield and the shield was moving through
the ground like this. In order to stay online
, it had to be at an attitude above the
the line on which it was driven. And that
was causing the settlement because it had a big hood
on the front that was taken off. And it
was able to in the next run to go and
reduce the settlements dramatically. But we got a picture
of the ground movements throughout the soil mass. It
was something I worked on that project with Bill Hans
Meyer. We've, uh, been an engineer working
with PB and, uh, well known for the
contributions. He has made an underground construction over the
years. Here's here we are in 2000, and
we had a tunnel where we were monitoring pore pressures
and clays in the Chicago clay and also settlements.
And this is just the short term settlement. I
won't get into the consolidation settlements here in this lecture
, but what we had was at the front of
that shield small displacements. And now you're not talking
about the surface settlement point because that spreads things up
so you can't tell from the surface settlements where it's
occurring around the shield. But what we're trying to
do is figure out what's happening right down here at
the Shield at the location of the shield, and
that tells us how much ground movement we're getting and
where it's occurring. In other words, we can
find the source of the movement. And so it's
a simple way of evaluating behaviour around a tunnel boring
machine. And we're using extents are meters or deep
settlement points on every project that we're dealing with with
these shields. Tunnel shields. And so here we
have the case. Where, over the top of
the shield, we have an inch and a half
of movement and this over cut. Or they have
to cut a larger diameter at the front than over
the shield so it doesn't get stuck, and so
it can turn. And so this, in this
case, was the over cut was about three quarters
of an inch on the radius, and it was
causing, um, that's the annual list, and
it was causing an inch and a half the settlement
when you take it around the full perimeter. And
so that was the cause of the settlement, and
that occurred every time we did a tunnel. If
we didn't cut down the over cut, we couldn't
cut down the settlement. That was something that stayed
with us. We could not get rid of that
. So you could. You could conclude that you're
going to have a deep settlement that could be of
that inch and a half level, and your surface
settlements are going to get up to an inch or
so. So if you have a three quarter inch
over cut here, it'll cause that part of it
causes three quarters of the surface. You can't get
away from it. So we have the face ground
lost, large ground loss concurrent to the face.
We have the over cut. We have the shield
itself, and the over cut can cause a volume
, displacement or volume loss and the tail. If
we don't install the lining rapidly, we can get
displacement there. And all of that results in a
settlement trough that just kind of three dimensional feature moving
forward and we can relate the volume loss to the
change in volume in the soil, and that has
to equal the surface settlement volume. So that's how
we approach evaluating this and then we can evaluate,
given that information in the shape, we can evaluate
the maximum displacements that will occur at the surface and
relate that the building damage our slopes and building damage
or angular distortions. So we're measuring groundwater pressures with
bizarre meters, and we're also measuring the location of
this ground loss. And in some cases, we
have many instruments in other cases, just a few
points above the tunnel. So, um, those
are the things that are some of some of our
precedents and, uh, where we've come from and
they've given us a lot. And I want to
talk a bit about the pressurized shields and what we
can achieve with that In 2006 on the Metro,
they basically had required that we no longer use open
shields. Dan Eisenstein, who was working with them
at that time he was up at Edmonton at the
university there for many years and just recently passed away
, and he basically, uh, was one that
said, we are going to use our pressure balance
shields in Los Angeles, And so they did,
monitoring all sorts of settlement cross sections, and basically
they found that the settlements range from 0 to 0.3
inches and the percentage of ground loss we're gonna figure
a percentage of the volume of the tunnel was less
than 0.25% of the volume of the tunnel. And
then that would produce angular distortions that would not cause
damage. And there was no damage. Very little
settlement. And why was this occurring? What was
making this? These small settlements were controlling the face
. But what's causing us to get very, very
small settlements here? And so here's some of what
we were looking at in Los Angeles and in 2
, 2011 and 2012. In the last couple of
years, we've had opportunity to do some more measurements
and observations on two projects. Sound transit in Toronto
, and those are the ones I wanted to focus
on right now, as we get into more detail
on the behavior that were occurring around these tunnels.
And so here we are in sound transit with Machine
by J. D. Uh, the the sponsor
on this joint venture. He's got the machine going
into the side of the shaft just starting here,
and this is in the glacial soils over ridden glacial
tills out Wash in Seattle, and he planned.
This is Mike the Pony with JD planned to use
a four inch over cut on the cutter head.
Well, three quarters of an inch is causing three
quarters inch at the surface. A four inch over
cut is going to cause perhaps something on the order
of four inches sound. Transit was not happy.
They said, You know, why are you doing
this? And and Mike said, Well, let's
do a test section And, uh, I had
I was working for sound transit over the last few
years, not anything active and very recently, And
I talked to some transit and I said, I'd
like to work with Mike and I said, Well
, we'd have to get account. I said,
No, I don't want to contract. I just
want to work with him. And so we worked
together and sound Transit was reviewing and cooperating, and
we basically had a great opportunity to understand. Learn
more about behavior. And here we did. We
had sensors that were on the body of the shield
. We put pressure sensors on the body of the
shield to figure out what's happening around the shield and
our art. Is that four inches going to cause
a problem here or what? What is happening around
the shield is the soil falling in around the shield
. That's what usually causes ground loss. And then
we had on the face earth pressure balance gauges,
which are always on the face. The earth pressure
gauges rather that are on the face, that measure
the face pressure so that we balance that that face
pressure needs to be at least equal to the water
pressure because we don't want the water flowing into the
fish. So that was the setup, and Mike
basically decided that on every extra Osama he was going
to put a vibrating wire prism butter in the bottom
of it. And we're doing that now and other
projects every time we put an extra Osama and we
put a vibrating where prisoners were monitoring the ground behavior
in terms of how the water pressure changes as we
advance the shield and that gives us a lot of
good information, we can correlate with what's happening with
the face pressure face Pressure gauges are right behind the
cutter head and on the on the wall of the
back of the chamber several feet back, where the
muck is being mixed and pressurized. And so here
we are. This is the test section that is
proposed at the start of the tunnel, right at
the start time, when you know you're not not
always up to speed, you're on a learning curve
and here's the tail section of this. This is
This is the trailing here that's on the order of
300 ft long that comes behind this that has all
the support that's required to advance that shield. That's
the sort of thing we're doing in modern pressurized face
tunneling, the screw conveyor looking in the other direction
. You see the screw conveyor. In this case
, there's temporary segments that have been placed to get
working, to react against the jacking frame, to
be able to push the machine into the ground.
So the machine is just in the ground, and
here we go. These are the experts on matters
that we have and the mikes bizarre meters that he
put in. And there's the building that we have
to be under control before we get to Yeah,
so machines starting out, going forward. They got
to these last kilometers, and the information we're getting
was very interesting. Here's the face pressure up at
the top and you can see the face pressure building
up to about 22 PC. That's during the time
that they're shoving and then after the show of the
only running one shift here because they've just started the
project. So after the show, if we have
it dropping down to about 12 p, S,
I and that's also happening on the body and the
over cut is doing the same thing. It's following
the same pattern as the face pressure. And then
we sample that we actually ran up because some small
equivalent of split spoon samples up into the thing and
took samples and see how much is disturbed material and
how much is the soil and we're finding in.
There were finding on that over cut the muck.
In fact, we had to stop doing it because
the money was flowing into the tunnel or into the
holes that we had in the on the body of
the Shield. This is back behind the cutter head
, and so we're seeing that we pressure the face
pressure is also pressurizing around the perimeter and that pressuring
of the perimeter is what's holding the ground. And
so then here we have the measure that kilometers in
the ground and they're following this and this bizarre meters
further further back, so it's not responding as much
. We have one kilometers right at this location.
It's showing it's going up and down pretty well.
It's following because it's near the face pressure. They're
working to get there, uh, working together.
And then we get to the point that they stopped
and they wanted to check and see if they could
go under free air to get out in front.
So they dropped the pressure on the face and here
we are, dropping the pressure. The pressures are
dropping to very low values, actually below the groundwater
pressure, and it has a check and then they
got pressure's dropped the next diagram. Then here's the
settlements. This is pretty boring information. If you're
doing a thesis, you don't want to have no
data or data. This isn't changing. You're going
along here. Nothing's happening. And that's what was
happening through the whole drive. No settlement, and
then we got to this point here and they drop
the pressure and this thing dropped down and this is
not a disaster at all. And it was just
a check anyway, at one location was settled 10.4
inches so that that mark that had been pressurized was
lost its pressure and allowed settlement at least a small
amount. And the material is still a material in
there. Perhaps the condition muck is still in there
. It would be the condition mark, but it
caused some settlement. And it just happened that they
stopped right over an extent somber, and you could
see that happening. So those things are all proving
to us that actually what is happening here Is that
the pressure on the face? The muck is going
around the perimeter and and here we have what's happening
. We have the condition mark in the front.
We have the segments in the back that are under
pressure. And so this is kind of like a
pressure diagram. I gotta pressure here pressure by the
grout that's being pumped until it sets its under pressures
that are higher than the face pressure. Usually so
everything that's under pressure. But what's happening in here
, and I don't think people paid much attention to
that. In some cases, it was the e
. P B might not put the muck out here
. In some cases it will, and that may
be the difference between best performance and lesser performance with
these machines. And so what we found was that
the conduct condition muck was filling and pressurizing that large
over cut, and it was flowing around the front
and into that gap, which in this case was
four inches thick, some of the great the greatest
gap I've ever seen on a machine. And so
we did have pressure there, and that's something that
you had to maintain 24 7 when the machine is
operating. When it stopped. As long as you're
below the water table, you maintain that pressure.
What, so here's what we're doing now with a
face were pressurizing the face that's preventing the loss into
the face Large movement, the over cut and the
tail is being pressurized with the grouting and with the
filling of the condition muck, and in some cases
we pump bentonite into that over cut to make sure
we've got that over cut filled and So that is
what has made it possible for us to tunnel with
essentially no settlement. Mhm so that that, to
me, is a part of the revolution. The
Revolution is being able to tunnel deep under water ways
and to be able to tunnel under control in very
shallow conditions. I want to go to one more
case here, Uh, in a moment, Um
and so? Well, in fact, now we're
talking about going under I five in downtown Seattle is
right up on the hill next to downtown Seattle to
our left, the University of Washington Over here,
Uh, the station. And what could be better
than having a train running from a downtown center to
your university? Um and so been champagne Orban at
University of Illinois. That doesn't happen. But here
they're crossing I five with 13 ft of cover over
here. The five crossing their under their deeper.
They've had no settlement going from Capitol Hill down to
the down to the I five and they're going under
with 13 ft of cover. And they basically at
that location. Uh, those are kind of a
diagram of the tunnels going into the I five and
they got through and I had about a quarter inch
of settlement because they were, so shall they had
to hold the pressure because they put in this condition
, which could be full. It's basically a soap
form. And the main concern of of the contractor
was not to put soap foam on an interstate highway
. She makes made a lot of sense, and
here we are now with the machine coming through.
That's the front end of that machine. That's the
cutter head after it's gone 4000 ft. And and
there's some some of the cutter's got knocked off by
boulders. There's been some where it's the where on
the perimeter went from four inches to about an inch
and a half, and the the the the entire
run was out was done without requiring cutter changes or
repair of the hard facing the surface of that of
that, the face of that cutter head. And
that was Mike's goal. The reason he wanted four
Inches was he wanted to get through this project without
having to do a lot of interventions under compressed air
into the front of his tunnel. He made it
. He made the whole distance without any without any
interventions. Mm. The last one is Toronto Transit
. And we had I had an opportunity a year
ago. You could see last fall, September and
October, uh, to work with Toronto Transit on
there. Um, it's Medina line. It goes
up by York University, northern part of the down
of the Toronto area and contract was O H L
. A Spanish contractor experienced in running earth pressure balanced
machines. The tunnel boring machine was, but I
love it now. Caterpillar earned, um, out
of Toronto up to date machine that was actually purchased
by the owner. And then we had to go
under this building. This is called the Shoelace Building
at York University and the distance below the clearance was
to the footings and foundation was 6 m about the
diameter, one diameter of the tunnel in the tunnel
of 6 m in diameter below that. So it's
a closer ah, passage closer, less cover than
we would normally expect to have. And so they
had proposed in these soils or silty sandy soils,
a lot of pretty sandy tails again, we're entails
over consolidated materials. You can see the distance to
the foundations there. And, uh, they ran
an estimate and said, Well, we expect to
have a volume loss of about 1%. Now.
What I mentioned was that in, uh, in
L. A metro, they were getting 0.25%.
But this was the estimate in the design was a
few years ago when they did the design. So
this is what they were estimating. And it's something
that I've seen in some other projects. And from
that estimate, they then figured, looking at the
shape and all this, you can figure you can
do numerical things. You can do it from our
experience, Uh, and you can come up pretty
much with the same result that's expected about 30 31
millimeters of settlement. And that would give you an
average slope about 3.4 times 10 to the minus three
, about one over 300. And they wanted to
have less than 10 millimeters settlement a slope of about
one times 10 to the minus 31 over 1000.
So at three times 10 to the minus three,
there are 1% volume loss. They're up in this
range and moderate damage, and they didn't want that
was higher than they wanted to. Um, have
the agreement with the university is that we will not
have that type of settlement. And so the one
thing that would happen is that the building stiffness would
reduce the distortions and spread them out so that it
would be lesser damage. But with with the grounding
that they proposed a compensation grouting, they were going
to get down into the very slight range, which
was acceptable. And so they laid out a program
putting in three shafts and the program. And if
you can see it here, these are all the
compensation ground pipes and their sleeve ports where you can
go out at any location along this as the,
uh, tunneling machine that would run across here.
And you're grounding as the tunneling machine runs keep moving
this ground up or holding it in place while the
tunnel drops it. And so these there's 100.
Boring is here, and I'm not sure the links
, but they get up into the well over 100
ft links on these borns horizontal boring, that are
going to be installed underneath the building. The problem
was that the contractor had arrived about 150 m away
to the left, and the ground pipes were not
in place. The problems with the subcontract and all
that for the granting the grout pipes were not in
place, and the contractor was, in the meantime
, doing pretty well. He was getting a couple
of millimeters 34 millimeters at the ground surface. So
what? So the question was, can he go
under the building? And we said, Well,
we haven't checked this out 6 m above the tunnel
, But let's take a look at this. And
so they said, Let's run test sections in these
two sections And that's what we did in September to
see if he could achieve the 10 millimeters without compensation
grounding. If we could do that before it's the
building, then we could perhaps go ahead. The
designer agreed with that, and here's the building itself
, as we're going to come in from the right
and then underneath your that. These are some fairly
massive concrete walls in the basement, and so the
stiffness of the structure is such that you would probably
reduce the angular distortions below the average ground slope,
maybe to to evaluate 40% of that ground slope,
so we'd expect even less than we would have outside
before we hit the building and the operator, uh
, one of the things I went in and saw
the operator's console, and I said, It's important
that we have target levels for various things and I've
been talking to send to the Toronto Transit people and
went in the tunnel, and there it was,
he had he had all this right on the wall
. This is what I'm I'm operating to the The
tunnel operator is not a lone Ranger, and they're
doing what he wants. He's following a guide,
the guideline for alert alarm levels for things such as
the EPB pressures, pressures on the face, the
muck weights. And the one thing that I noticed
was that they hadn't pumped and bentonite through the shield
. They could do that, but they hadn't done
it, and certainly we might get get the ground
or the condition mark going over the top. But
in sandy soils, I was afraid they might.
It might block. We wouldn't get as much consistency
with filling that over cut. So one of the
things we asked them to do is say go ahead
and use the bentonite as you advance and they didn't
do that. And here's some of the data that
they got. Basically, they drove through and as
they drove through the tunnel, This is what's happening
in a period. Here is 24 hours, and
they're they're making some very good progress here. There's
a whole series of advances in here, and then
they got to the day off here on Sunday,
and I'm not sure. I think it's maybe Saturday
Sunday anyway. The pressures are dropping, dropping off
, so as they stop, they hold the face
. They're not doing anything now. They're just holding
it in place. And what happens is the pressure
in the face begins to drop down to the water
pressure. The more rapidly it drops, it would
be the more permeable the soils are, and so
so that is an indicator of what the actual ground
water pressures are, and they're operating above that.
And that means that they are balancing the water pressure
and even adding some active pressure to reduce small movements
into the front of the tunnel. And so that's
one of the indicators. If at the end of
the show. Those water pressures go up, you're
in trouble. You probably lost ground. And so
that's the sort of thing that one of the indicators
of what you look at and, uh, here
they are now spread. I took that diagram and
spread it out of it, and you can see
each shop. So this is one shelf was bouncing
up and down. That's the end of the shove
waiting for the next show, and it's drops off
a little bit. And then the next one and
the pressures go up and down a little bit.
Uh, the lower pressure gauges show the highest pressure
, of course, and and they're they're they're doing
things a little different because the weight of the material
in the head is different than the weight of the
soil, the density of the soil. So you're
going to have a different gradient across the face of
the muck inside the head than you do in the
face in the water, and that causes some variations
between the gauges. Here we are, in one
case, I wanted to show you, and then
you get to the end of the drive and it's
almost a repeat of Seattle. They dropped the pressure
because they were going before they went into the building
. They're going to go through a head wall or
a place where they could check the cutters. Uh
, lean concrete mix wall, and they dropped the
pressure and they happened to have another extra Salvador right
at that location. And this is what it showed
. It showed. Instead of settlements of zero,
it's suddenly dropped over the top of the shield,
where they dropped the pressure at that exact time and
they got immediate settlement of eight millimeters are about it's
, you know, a third of an inch and
and then we went back and evaluated all the all
the pressure, all the, um, all the
data that they had over the entire run. And
this is the first Dr Plan view, Second drive
and those numbers. I put those up and say
, Well, that's the settlements. And so yeah
, well, we think in the English system and
we say, Well, this is one inch two
inch three inches. No, these are millimeters.
We had four millimeters settlement three millimeters Settlement two millimeters
. On the second drive, they put the pressure
up to millimeters settlement over the entire drive. Very
consistent results as they went through there. So the
question was, Can we go under the building now
? That looks excellent. The other thing that was
so excellent is the consistency of the operation. Consistency
is the key to me. It's not that you
managed to do it once. What am I going
to do when I go into the building? The
consistency of the opera control was something that it made
it very apparent that they could go into that building
. And they did. And so what? We
measured in the test section. We're down here in
this range and they went through the tests. This
is actually going under the building now, I think
, Yes, they we made the recommendation, went
under the building. And here is the damage level
. Half to one millimeter. You could actually see
the ground, heave half a millimeter and then drop
very precise measurements on the inside, the inside the
building, and drop maybe a millimeter as the TBM
went by. Uh huh. Outstanding performance without any
compensation. Grouting. No drilling of conversation. Ground
holds no compensation grouting and later conversation. Grounding.
Trying to put conversation ground pipes under another part of
one of the structures. They got at least five
millimeters settlement due to the installing the compensation grab.
So the tunneling is was doing a better job than
the installation of the protection measures. Well, I'm
working on the metro and and usually working with talking
to a group of scholars, people that are writing
thesis and you're referencing everything is this is not This
is not a reference list. These are credit.
So this is this is Hollywood, you know,
roll credits. So I just wanted to do that
. Okay, we start out with the Thames Tunnel
, we have to give credit to Queen Victoria here
and the city of Chicago in the 1939. Those
are the key people. That that was the That
was my president. When when I was in school
, we're talking about They were telling us about that
project. So I was learning not just from my
experience, but from that of my mentors. And
that's that's the way we work in our in our
in our profession and geotechnical engineering. Civil engineering,
Washington Metro. We made the measurements with a number
of scratch students uh, Evanston. We had Larry
Lenin ham with McNally tunneling that supported our research and
ui thesis on it. And then, uh,
Dan Eisenstein in l. A key to making the
transition into the earth Pressure balanced systems in Seattle.
The people working on that project and Nissan from Penn
State is doing a thesis there and was out there
working on the project. And here's some more.
These are the credits for Toronto, and I asked
, uh, Hussein bin Handy that really organized this
and coordinated all this This effort and that was part
of this is coordination and interaction between the Geo Tex
and the machine people, the contractor. And,
uh, that's those are a lot of the people
that worked on that project. I wanted to go
just a brief couple of brief comments in the minute
that is left a minute or two. Is that
control and design, or how do we design for
control? And one of the toughest parts about our
engineering profession is designing to achieve the results that we
so that we achieve the results that we have been
committed to. We're making committed commitments to third parties
to the people around in the community were saying,
We can do this without damage to your building or
with small cracks and won't be any structural damage.
And so so why should they trust us on this
? And how do we ensure that as we go
through a contract process, we can tell through the
contract and through our interaction with the contractor, how
can we tell? Tell him what to do or
or or given the guidelines that he will achieve what
we promised, and that, to me, is
one of the important things about our profession to ensure
that this tunneling will be under control. That's why
people went and put in the conversation grounding and said
, We don't know where the contractor will achieve this
. We're gonna put in something that will take care
of it. And so that's the way the designer
thinks about the project. And so this is kind
of the way it goes. The owner and provides
the contract delivery methods, the project design. It
may be a preliminary design if we have a a
design build project because the contractor, maybe a designer
as well and then he's preparing specifications. He's doing
project management and he wants to do that so that
the tunnel contractor achieves the ground control minimizes impacts consistent
with the owner's commitment to the third parties. Uh
huh. And the owner, the owners. The
third parties have been interacting, particularly the Metro.
You're having community meetings. There's all sorts of things
going on. Can we tunnel under Beverly Hills High
School? Well, that's an issue that Beverly Hills
High School is going to be and has been very
involved with. And that goes for other parts of
a major project. And one of the things that
came out was a man. Mr. Singh had
a had a Capitol building there at the end of
the other Dr Going into Capitol Hill. This is
the Trailer Frontier Kemper job that came out of the
station right next to a heck stadium at at the
University of Washington Football Stadium came across and to Capitol
Hill. And just before you get the Capitol Hill
, it was the capital building. It's a nice
brick bearing wall structure, four stories, high apartment
structure, department buildings, and we reviewed it several
times, and we can investigate this and reviewed it
. We determined that NPM telling could be accomplished.
We're going about 40 50 ft below and without having
to do conversation grounding now the shaft is right over
here to the right. And so we could have
if we had had to. We could have put
in long holes across here, but we felt that
it really was not needed, that we could tunnel
under control. And, uh, then the question
was, is trailer meeting that criteria And they we
watched their performance. They were, as they approached
, their tunneling was under control. They weren't getting
ground settlement of any significance. And so they continued
. And, uh, this was the paper two
days a day before Seattle Times, the day before
they tunneled beneath the building and he was still expressing
concerns. And he had consultants. He had geotechnical
consultants working with him and people saying, You know
, trying to evaluate the issues and sound transit People
were, uh, with Mr saying when he was
when the tunneling went through and keeping an eye on
things. And so he said he had indicated that
he was at least some transit said, Well,
the building owner is fearful, and I mean,
it's his building, you know, and the sound
Transit has either gotten an easement or has condemned an
easement to go underneath his property. And so this
is what we have as engineers we have to deal
with. This is a public. These are public
issues or issues with our projects, and that's that's
a major part of heavy construction of the type of
work we as civil engineers do. And so and
on the 21st, the day after the sale,
Times reports that the tunnel drivers successfully achieved with.
And I don't have exact numbers on all the information
but no significant effects. And the comment came from
people working with Mr saying that it performed better than
perhaps they had anticipated. This is the shaft that
they came back into, and here, this is
the one that the other contractor had started out to
go down. JD had gone across here from,
um, had had driven, uh, with the
four inch over cut. So these are some of
the things that we do in control and design we
focus on, uh, we note that that our
first focus should be on the machine and controlling it
. We may do other things, but that's our
first focus, and these are some of the other
things that we do to make it work. And
so the question is, have we met Bernal's objective
? And it's not that we did meet it.
We if we're gonna meet it, if we're gonna
have no ground loss, we have to do certain
things. And so it's being achieved with the capabilities
of these machines, with the electronic monitoring with understanding
those machine functions, not a bunch of data that
you don't know how to evaluate. And with this
coordinated team effort and controlling and operating it, the
operator is not working alone. We have monitoring coordinated
team effort in real time, and that's what we're
dealing with the Alaskan Way Viaduct. And that's why
it's possible now to build the world's largest, uh
, earth pressure balanced tunnel in downtown Seattle. Because
we're able we were able to achieve Ah, it's
not just that we can go and do it with
. We have these things in place for evaluating as
the project goes on. So I've enjoyed time talking
with you, and that's at the end of the
presentation. Do we have time for questions? Want
to interrupt the food back there. So important things
. First, a couple questions. Dave. It
is the extended over cuts, something that's being more
widely looked at in the industry, with other contractors
being on board with that. Not necessarily. It
could be. I mean, he did that because
he was able to cut where, particularly in the
gravelly bouldering ground. But I think the thing that
the point that I've made here is that that he
was able to get that material into the over cut
. But I think that what we're if we're if
we're uncertain about it, we're requiring that they pump
the bet night and keep it under pressure. So
we have that, and we're requiring that on all
all our projects now. And that's the difference between
three quarters of an inch. Settled under or not
is that they confessed to us that they used the
larger over cut on the project in Ohio without telling
anybody, and found it helpful. Syracuse. I
was on the dispute reviewed for that as Dave Dispute
Review board for that, as Dave Walls knows that
well knows. And so we've had discussions after the
fact, and he was trying not had a shafts
down. He didn't want to hit. It was
going between a couple of shafts. You don't want
to go down in the shaft and take care of
the machine is going to jump a shaft. And
so I think that's when he decided you don't put
a little bigger cutter on bigger overcome. The other
question we had, uh we had, uh,
had somebody out. There is a kind of a
shell to give me a question, and then she
won't go there. There you go. Yeah,
I would have been nice if you could share with
us your thoughts. And why is it that people
service structure I'm serving? Yeah. We were talking
about this at lunch. It's interesting, because just
briefly, you know, when you build, when
we build high rise structures, we build your parking
garages. We build beams. Uh, a 10
in the 10th or 12 10, 12 centuries.
They built arches, big arches for the gorgeous cathedrals
. Couldn't take any attention. They build arches,
And in order to make the art stable, they
put on buttresses flying buttresses. We can't build a
high rise like they built cathedrals. And so our
structural engineers build beams and maybe a trust or whatever
. It's still a beam and they can go hundreds
of stories up in there. And so when we
get to the underground, what do we do if
you put a beam in on the underground? The
loads are way above on a beam with soil,
10 ft of soil is far above the loads that
are out floor loads of several£100 per square foot
for other structures and for high rise structures. And
the other thing is, we have an infinite buttress
. We've got buttress all around us, so we
build arches underground and we get that reaction from the
ground. And, uh, that reduces the moments
and you can you can build it. We can
, I can. We can build tunnel endings without
any any reinforcement. Some cases we do in other
cases. We want to make sure we reduce yeah
, fractures with the reinforcement, so that's very interesting
. And it's a little different than what a structural
engineer thinks about when he's doing above ground structure.
That's kind of an aside. It doesn't quite follow
this, and I know why. You didn't want
to mention it, but I just thought that we
you thought it was something worth discussing. Okay.
Okay. Dr. Corday, I'd like to leave
you with this, This hat. So when you're
out in Seattle, you'll remember where to find the
brightest future engineers to work on these projects. That's
excellent. Are you all willing to go west?
I mean, you've had some good faculty that have
come west to east. You know that some of
our colleagues here, uh, it's not a bad
place to visit, But you don't want to stay
out there. Thank you very much as well.
That's wonderful. I appreciate that. That's excellent.
Good. Thank you. Very. Thank you very
much. That complaints that part of the afternoon.
Thank you very much, Ed and and Alan again
. And I don't know if you all have turned
your head and look to the back of the room
, but there's quite a bit of good looking food
back there. And so I hope you'll partake.
Partake of that before you leave here. Thank you 1285 --> A:middle L:90% .