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The Asphalt Core Embankment Dam A Very Competitive Alternative. Prof. Dr. Kaare Höeg Norwegian Geotechnical Institute (NGI) and University of Oslo Athens, Greece,19 Nov. 2009. Svartevann Earth Core Rockfill Dam (129 m), Norway. Svartevann Dam under construction.

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The asphalt core embankment dam a very competitive alternative

The Asphalt Core Embankment Dam A Very Competitive Alternative

Prof. Dr. Kaare Höeg

Norwegian Geotechnical Institute (NGI) and University of Oslo

Athens, Greece,19 Nov. 2009


The asphalt core embankment dam a very competitive alternative

Svartevann EarthCoreRockfill Dam (129 m), Norway



The asphalt core embankment dam a very competitive alternative

OddatjörnEarthCoreRockfill Dam, Norway (145 m)




The asphalt core embankment dam a very competitive alternative

Storglomvatn Dam nearcompletion (125m)



Experience with asphalt core dams
Experience with Asphalt Core Dams

  • 100 dams have been built, most in Europe and China, now also in North and South America;

  • 20 are currently under construction or final design;

  • first ones built in the early 1960s (Germany and Austria;

  • 15 built in Norway; 3 more are now under construction/final design;


Field monitoring
Field Monitoring

  • - The first dams with asphalt core were heavily instrumented and thoroughly analysed to better understand dam and core behaviour.

  • - Field performance has been excellent, with no recorded leakage through core or the core-plinth interface at the base of the core.


Laboratory testing of asphalt concrete
Laboratory testing of asphalt concrete

  • For each new dam and site tests are performed to determine the optimum asphalt concrete mix using:

  • the available (local) aggregates (0-18 mm);

  • filler material (0 - 0.075mm);

  • grade of bitumen available.

    • The goal is to achieve a core with low permeabilty and flexible and ductile stress-strain behaviour with the required strength.


Laboratory testing cont d
Laboratory testing (cont’d)

  • Full advantage has been taken of all the laboratory and field research done for asphalt concrete used in road- and airfield pavements.







Test to create crack in specimen
Test to create crack in specimen strain before crack opens





Triaxial test cyclic loading superimposed on static loading to simulate eartquake loading
Triaxial test – cyclic loading superimposed on static loading (to simulate eartquake loading)


Cyclic strain and residual strain during test
Cyclic strain and residual strain during test loading (to simulate eartquake loading)


Pre cyclic vs post cyclic stress strain behaviour
Pre-cyclic vs. post-cyclic stress-strain behaviour loading (to simulate eartquake loading)

Deviator stress (MPa)


Asphalt concrete placed in core
Asphalt concrete placed in core loading (to simulate eartquake loading)

  • Air porosity in asphalt core should be less than 3% to ensure very low permeabilty (10-10 m/s);

  • Placed and compacted in layers 20-30 cm thick;

  • 2 to 4 layers per day depending on required rate of construction;

  • Core width usually 50-100 cm depending on height of dam.


Asphalt core placing machine paver
Asphalt core placing machine (paver) loading (to simulate eartquake loading)


Asphalt core paver principle sketch
Asphalt core paver – principle sketch loading (to simulate eartquake loading)


Preparation of concrete plinth placing mastic
Preparation of concrete plinth (placing mastic) loading (to simulate eartquake loading)


Hand placement of first layers
Hand placement of first layers loading (to simulate eartquake loading)


The asphalt core embankment dam a very competitive alternative

Machine loading (to simulate eartquake loading)placement starts


Test strip on site prior to core construction
Test strip on site loading (to simulate eartquake loading)prior to core construction


Compaction with 3 rollers
Compaction with 3 rollers loading (to simulate eartquake loading)


Field samples 0 5 m long drilled out of dam core no interface can be detected between layers
Field samples (0.5 m long) drilled out of dam core loading (to simulate eartquake loading)(no interface can be detected between layers)


Cutting field core into 5 test pieces
Cutting field core into 5 test pieces loading (to simulate eartquake loading)


Controlling field porosity
Controlling field porosity loading (to simulate eartquake loading)


Field control laboratory
Field control laboratory loading (to simulate eartquake loading)



Porosity control without sampling
Porosity control without sampling drilled out of the core


Excavated core from field test strip
Excavated core from field test strip drilled out of the core



Demonstration of core flexibility cont d
Demonstration of core flexibility drilled out of the core(cont’d)


Effect of laboratory method of compaction on resulting stress strain properties of asphalt
Effect of laboratory method of compaction on resulting stress-strain properties of asphalt

  • Triaxial results from laboratory prepared and field core specimens with the same air porosity have been compared.

  • Differences in behaviour must be considered:

  • - if stress–strain design requirements (compression modulus, degree of shear dilation and ductility) are based on test results from laboratory prepared specimens;

  • - and if finite element analyses are used to predict or back-analyse core behaviour.


Effect of laboratory compaction procedure how to best simulate field compaction in the lab
Effect of laboratory compaction procedure (how to best simulate field compaction in the lab.)


The asphalt core embankment dam a very competitive alternative

Storglomvatn simulate field compaction in the lab.) Dam nearcompletion (125m)


Zoning of storglomvatn dam 125 m
Zoning of Storglomvatn Dam (125 m) simulate field compaction in the lab.)

  • 1. Asphalt core 2. Transition (0-60 mm)

  • 3.Transition (0-150 mm) 4a. Quarried rockfill (0-500 mm)

  • 4b. Quarried rockfill (0-1000 mm) 5. Slope protection (blocks, min.0.5 m3)

  • 6.Crown cap (blocks) 7. Toe drain (blocks, min. 0.5 m3)

  • 8. Concrete plinth (sill) for core


Yele asphalt core dam 125 m china
Yele Asphalt Core Dam (125 m, China) simulate field compaction in the lab.)

Fig.5


Core cutoff connection at yele dam china
Core-cutoff connection at Yele Dam, China simulate field compaction in the lab.)


Special testing of core plinth interface
Special testing of core-plinth interface simulate field compaction in the lab.)

a)

a)


Back calculated max shear strain in core of yele dam
Back-calculated max.shear strain in core of Yele Dam simulate field compaction in the lab.)


Optimum design considerations
Optimum Design Considerations simulate field compaction in the lab.)

Which embankment type is best suited for the local conditions, considering:

-economy (construction and maintenance);

- safety/reliability;

- impact on the environment.

The local foundation/geologic conditions will have significant impact on the choice of dam.


The asphalt core embankment dam a very competitive alternative

Different embankment dam designs simulate field compaction in the lab.):

  • - earth core embankment dam (ECED)

  • - asphalt core embankment dam (ACED)

  • - concrete faced rockfill or gravel dam (CFRD)

  • - geomembrane faced embankment dam (GFED)

  • - faced hardfill dam (FHD or CSGD)

  • Recent comparisons among alternatives show the ACED to be very competitive.


Asphalt concrete core
Asphalt concrete core simulate field compaction in the lab.)

  • - Simple and robust construction method;

  • - Asphalt concrete is a flexible and ductile material with viscoelastic-plastic properties (a “forgiving” material);

  • - No core erosion; therefore no strict filter criteria;

  • - Core adjusts to dam and foundation deformations;

  • - Earthquake resistant; no deterioration of properties;

  • - Self-healing (self-sealing) of any cracks;

  • - Asphalt mix may be ”tailored” to satisfy special design requirements;

  • - Can resist overtopping erosion during construction;


The asphalt core embankment dam a very competitive alternative

Thank you simulate field compaction in the lab.)

for your attention