Viaduct I Failure, Caracas

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Viaduct I Failure, Caracas La Guaira Highway,
Venezuela
Ali Jabalameli Yaút Peña Pattanun Chanpiwat
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Introduction

• Viaduct No.1 was completed in 1953.
• The main part of structure consist of three
  parallel arch ribs of a hollow box type, with a
  hinge to hinge span of 152 m and a height of 70
  m.
• The southern pile was founded on vertical
  concrete shafts and three inclined concrete
  piles.
• The pilaster and the arch on the northern side
  were founded on a raft foundation.

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Behaviour of the southern slope 1953-1987

• Landslide in 1974 that affected many low income
  houses.
• In 1981 a landslide occurred in the upper part of
  the slope, located 250 m south of the Viaduct.
• An asphalt bump formed along southern abutment on
  April 1987.
• Geotechnical investigation, including
  photogeology, borings and slope instrumentation
  was carried out.

1974 Landslide
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Photogeology

• Aerial photographs carried out between 1936 and
  1983 were carefully examinated.
• Scarps, stepped topography and color tone
  contrast of the slope were evidence of an ancient
  , 500 m long landslide.
• A meander in the channel of Tacagua creek at the
  bottom of the slide served as physiographic
  evidence of the slope movement.

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Geology and exploratory borings (prior to 1987)

• Material of the slope Colluvial material
  derived from ancient landslides.

• Rock Mass Limestones interfoliated with
  calcaroues mica schists, quartzites and some
  amphibolites.

• Main Geological Feature East - West Fault.
  Considered geologically active and responsible
  for some earthquakes in central Venezuela.

• Strike Parallel to strike of slope.
• Dip Direction 15-40 North

Colluvium
Limestones
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Emergency works in 1987

• On the south abutment

• 245 passive anchors. 1 3/8 diameter grouted
  bars. 30 36 m long. 3 m into rock.

• 20 prestressed cable anchors.

• Only constructed to divert the landslide thrust
  from the bridge.

• On both sides

• Opening of the expansion joints to reduce the
  positive bending moment on the northern side.

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Geological Exploration 1987 - 1988 Observations

• Movement of rock blocks along foliation planes
  at low dips (10-20).

• Tectonic slickensides.

Evidence of the intense tectonic history of the
area.

• Local fault breccias.

• Fault Breccia 50 m wide in a direction parallel
  to the displacement vector of the landslide.

Two inclinometers revealed the presence of a well
defined failure surface
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Surface Movement Monitoring
Instrumentation

1. 3 bench marks opposite side of valley
2. 15 control reference points on the surface
3. 56 control points on the deck
4. 4 control points on pilaster s and abutments

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Prediction of failure
Prediction based on Fukuzono (1985 ) and
Voight (1989a,b) Ration between rate of soil
movement rate of arch closing
Method collect rate of soil movement
(cm/month) plot the invert of velocity against
time (month/cm)
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Effect of landslide thrust on Viaduct No. 1Why
does it fail?
Cause
Slope movement of reactive ancient
landslide Moving of Viaduct No.1 southern side
increase distress in the structure The
structural geologic setting influence and
rainfall infiltration Structure is designed to
resist compression stress not for tension forces
Action
Replacement of northern concrete abutment and
piers with steel trusses with rollers (allow
to move freely ) Replacement of original
concrete rockers with steel struts (resist
tension) Construction of a cable system placed
in U shape grabbing between two piers ( support
of transverse shear failure releasing energy
stored in the decks)
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Series of Actions
August 2005
December 2005
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Question ?
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References
Salcedo, Daniel. "Behavior of a landslide prior
to inducing a viaduct failure,
Caracas-La Guaira highway, Venezuela."
Engineering Geology. 109. (2009) 16-30. Print.