PhD Defence PowerPoint - Ricardo Neves Correia dos Santos

1
Experimental Investigation on Limitation of the
Progression of Internal Erosion in Zoned Dams

• by
• Ricardo N.
• Correia dos Santos
• ricardos_at_lnec.pt
• Under scientific supervision of
• Dra. Laura Caldeira
• Dr. Emanuel Maranha das Neves
• PhD
  thesis prepared at
  

PhD thesis defence 29th October, 2014
2
Question Objective
Question Objective
Research question What is the influence of the
upstream zone limiting the progression of
internal erosion through a crack in the core

?
Sandy gravel
Sandy gravel
Filter
Upstream zone
Core
Upstream zone
gt Flow-limiting action gt Crack-filling action
gt Flow-limiting action gt Crack-filling action
gt Flow-limiting action gt Crack-filling action
Objective Experimentally investigate what are
the upstream materials that may provide these two
actions
3
Previous laboratory testing on erosion in soils
by others
gt Erosion along a concentrated leak
gt Erosion of an immersed soil
JET Erosion test Hanson and Cook (2004)
Hole Erosion Test (HET) Wan and Fell (2004)
gt Identification of dispersive clays
Pinhole test Sherard, Dunningan and Decker
(1976)
4
Previous laboratory testing on erosion in soils
by others
gt Susceptibility to suffusion of a soil
Upward Flow (UF) seepage test Wan and Fell 2008
Downward Flow (DF) seepage test Wan and Fell 2008
Sample Ø 30 cm h 30 cm
Drainage layer
5
Previous laboratory testing on erosion in soils
by others
Previous laboratory testing on erosion in soils
by others
gt Filtering in a hole
gt Filtering in a crack
Continuing Erosion Filter test Foster and Fell
2000
Crack Erosion Test Maranha das Neves (1989, 1991)
Crack filling by upstream uniform sand
6
New test cell developed at LNEC Two laboratory
tests
New test cell developed at LNEC Two laboratory
tests
gt Test Cell
gt Flow Limitation Erosion Test
gt Crack Filling Erosion Test
CFET
FLET
7
Specimen preparation cell assembly Tests
setup
Specimen preparation cell assembly Tests
setup
gt Specimen preparation in FLET
gt Specimen preparation in CFET
gt FLET setup
gt CFET setup
8
Experimental study in the FLET/CFET (Soils tested)
gt Upstream material
9
Experimental study in the FLET/CFET (Soils tested)
gt Core and Filter
2 Filters
2 Cores
10
Experimental study in the FLET/CFET (Soils tested)
gt Characterisation of soils used in the FLET/CFET
11
Experimental study in the FLET/CFET (Soils tested)
gt Erosion behaviour of gap-graded soils in the
simpler UF test
12
Experimental study in the FLET/CFET (Soils tested)
gt Erosion behaviour of the core soils in the
simpler HET
Core4
Core20
13
Experimental study in the FLET
gt Testing conditions
33 FLETs
1 year 3 tons of soil
14
Experimental study in the FLET
gt Observed behaviour types Type F1 Flow
limitation (self-healing)
15
Experimental study in the FLET
gt Observed behaviour types Type F2 Flow
limitation (non-erodible)
16
Experimental study in the FLET
gt Observed behaviour types Type F3 Slow down
of erosion process
17
Experimental study in the FLET
gt Observed behaviour types Type F4 Strong
progression of erosion
18
Experimental study in the FLET
gt Observed behaviour types Type F4 Strong
progression of erosion
19
Experimental study in the FLET (Conclusions)
gt Critical parameters influencing the
flow-limiting action
Fines content ()
Gravel content ()
w wopt ()
20
Experimental study in the FLET
gt Proposed rules for estimation of likelihood of
flow limiting action
21
Experimental study in the CFET
gt Testing conditions
41 CFETs
1 ½ year 4.5 tons of soil
22
Experimental study in the CFET
gt Observed behaviour types Type C1 rapid
crack-filling
23
Experimental study in the CFET
gt Observed behaviour types Type C2a Filtering
after some erosion
24
Experimental study in the CFET
gt Observed behaviour types Type C2b Filtering
after excessive erosion
25
Experimental study in the CFET
gt Observed behaviour types Type C3 Continuing
erosion
26
Experimental study in CFET (Conclusions)
gt Critical parameters influencing the
crack-filling action
27
Experimental study in the CFET
gt Proposed rules for estimation of likelihood of
crack-filling action
28
Final conclusions
29
Future research
30
Progression of internal erosion in the embankment
Tunbridge Dam, Australia Zoned earth dam (28 m)
Source Jeffery Farrar (2005)

Hanson e Hunt
(2007) Homogeneous
dam (25 m)
Source USDA
31
Experimental Investigation on Limitation of the
Progression of Internal Erosion in Zoned Dams

• by
• Ricardo N.
• Correia dos Santos
• ricardos_at_lnec.pt
• Under scientific supervision of
• Dra. Laura Caldeira
• Dr. Emanuel Maranha das Neves
• PhD
  thesis prepared at
  

PhD thesis defence 29th October, 2014
32
Importance of internal erosion in embankment dam
safety
gt Overall statistics of embankment dams failure
gt Population of dams worldwide
Population of 11200 embankment dams
Failures 1 in 200 (0.5) Accidents 1 in 60
(1.5)
Internal erosion
Source International Commission on Large Dams
ICOLD (2013)
Source Foster, Fell and Spannagle (2000)
33
Dissemination of thesis
4 International papers
1 Paper in PT journal
4 Conference papers
2 accepted Geo Test Journal (ASTM) 2 under
review J Geotech Geoenv Eng (ASCE) Géotechnique
(ICE)
1 Award
34
Experimental study using the FLET CFET
gt Observed behaviour types Type C3 Continuing
erosion
CFET GA3.GD12
35

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