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Instrumentation of the TEO

(Tunel Emisor Oriente)

East Sewer Main Tunnel

Mexico City

Rob Taylor, B.ASc. P.Eng.

President, RST Instruments

Georox 74

RST Instruments Ltd.

Head Office: Maple Ridge, British Columbia, Canada

Mexico City/Distrito Federal

3rdlargest urban center in the world

8.8e6 / 21e6 population city/metro

1500 km2/ 7800 km2area city/metro

4e6 cars

Sewer peak flow 315 m3/s (sanitary + storm)

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Geologic Setting

Once, Mexico City was a island in a large lake

The lake was >100 km long in a 2200 m

plateau surrounded by 5000 m volcanic peaks

The lake is gone, groundwater extraction has

caused massive (9m) settlement in the soft

clays to 40 m

http://localhost/var/www/apps/conversion/tmp/scratch_7//upload.wikimedia.org/wikipedia/commons/b/b3/AerialViewMexicoCity.jpg

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TEO Project

7 m ID / 8 m bored tunnel

62 km long

150 m3/s capacity

Depths 15-140 m (gradient/basement)

24 shafts, 6 TBMs, 6 contractors

230e9 pesos -> $18e9

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Shaft Construction

24 shafts

Typically 12 m ID, 16 m ID for TBM launch

Made by slurry wall, steel ring beams

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Shaft Instruments

Inclinometers

Strain Gauges

Vibrating Wire

Embedment Gauge

Vibrating Wire

Push-in Piezometer

Vibrating Wire Sensors

Common in geotechnical applications

Response is as frequency change, not voltageor resistance

Excellent immunity from wet cable conditions

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R

F

v

L

F

sin2FFR

R

L

2sin

R

LFF w

R

R

Lvm

R

LFF wwR

2

m

Fv ww

w

ww

w

ww

wwww

E

Lf

A

AEfL

2

1

2

)( 22

0 ffCFs

Vibrating Wire

Physics

+VE

FACE

A1. POSITIVE DEVIATION VALUE I I I

UPPER

WHEEL

Inclinometer

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Actually the Mexican approach is very

good:

Tough

Dry Accessible

TBM Tunnels

All drives are EPB TBMs

Ground support is by precast concrete lining

Lining is machine placed in the shield directly

behind the cutterhead and grouted

Secondary CIP lining slipcast to protect precast

mechanicals

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Tunnel Lining Instrumentation

External Loading

Internal Response

Global Response

Vibrating Wire

Tunnel Lining

Total Stress Gauge

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Rigid Body Lining Response

The rebar and concrete strain gauges measure

response within the lining sections.

What about the relative movement at the

joints?

The response takes place soon after

placement, but access near cutter is tough

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Space is Tight

TBM mechanicals 95 m long, absolutely packed

Any diametral instrument (tape extensometer

etc) will never fit

We came up with a lining response system

based on sensing the tilt on each segment

Devices are bus-based, so connections are

daisy-chained, 4 pin connectors, goes in very

quickly, up and running in

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What is MEMS?

Micro Electro-Mechanical System

Sensor and electronics are made in one

piece using microelectronic fabrication

techniques

For now, tiltmeters

MEMS Tiltmeters

Really a DC accelerometer: a = g sine (a)

Sensitive Axis ~ horizontal, asmall

Consists of:

Suspended mass

Spring suspension

Capacitive position sensor

Oscillator

Demodulator Amplifier (with calibration DAC etc.)

All on a single small block of silicon

M

MEMS Up Close

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Instrument Summary

Instrumentation of the shafts and primary

lining segments has gone very well Long-term monitoring is challenging, as

distances, pressures, maintenance will be very

adverse

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REVESTIMIENTOSECUNDARIODEFINITIVO

INYECCIN DECONTACTODOVELA-SUELO

EJE HASTIAL DEL

TNEL AINSTRUMENTAR

RASANTE DEL TNELA INSTRUMENTAR

DE EXCAVACIN

REVESTIMIENTOPRIMARIO

EJE HASTIAL DEL

TNEL AINSTRUMENTAR

CLAVE DEL TNEL AINSTRUMENTAR

RADIO

Progress Report

Theyve had a rough time of it!

3 years behind One shaft was flooded by overflow of adjacent

canal, yes, that is sewage!

All that sediment, water requires EPB TBM

But theyve hit a lot of rock, heavy going

Basalts and tuffs, need more powerful

machines $$$, time, politics

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In the News

The Good News

Best news is: so far rock is not associated with

major water problems

Over 60% of tunneling done, secondary lining

going in

First drive is completed, in service

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Whats Next

They have been recycling machines from

completed sections to speed up

New tunnel completion date is 2015, sewer

commissioned 2016

Next up: Tunel Poniente

Conclusions

Instruments provided valuable data on external

conditions, structure FS and response Because of the automated/prefab nature of

construction, observational method is risk

management for design

Integrating instruments into construction

systems reduced associated delay, improved

capture of early response

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Questions?