Pina Nicoletta De Cicco, Luca Solari, Enio ParisDepartment of Civil and Environmental Engineering, University of Florence, Italy

Bridge clogging caused by woody debris:

Experimental analysis on the effect of pier shape

Padova, Italy, 06-10 July 2015

THIRD INTERNATIONAL

CONFERENCE ON

WOOD IN WORLD RIVERS 2015

Carraia Bridge,

Florence (IT),

August 2014

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

The Point

Salmonie river, Montpelier

Taranto, Italy (2013)

Moncalieri, Italy (2008)

Borgo a

Mozzano,

Italy (2014)

Firenze, Italy (2014)

Thompson

Canyon River,

Colorado,USA

(2013)

Hazleton, Indiana,

USA (Source:Lyn et al. 2007)

Montpelier, Idaho,

USA (Source:Lyn et al. 2007)

Crandall, Indiana,

USA (Source:

Lyn et al.

2007)

2/18

The Point

Increase in water depth upstream of

a Large Woody Debris (LWD) jam.

Effect of debris on bridge pier scour.

Costs of woody debris removal.

Wood accumulation improves water

quality and sustains refuge habitats to

protect biota during pollution episodes

(Gurnell et al., 2002; Gurnell, 2014).

The presence of organic debris positioned

in proximity to the banks can protect them

from erosion (Smith, 1976).

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

Wood deposition (on left) and removal (on rigth) at Carraia Bridge in

Florence, Italy (2015)

3/18

The Point

Accessibility to the bridge!!!

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

Devil’s Bridge, Borgo a Mozzano (Lucca, ITALY). January, 2014.

4/18

What has been done in literature

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

Effect of woody debris (WD) dams on

bridge pier scour Diehl (1997), Lagasse et al. (2010),

Melville and Sutherland (1988),

Abbe and Montgomery (1996)

• Scour around a cylindrical pier Dongol (1989)

• Scour at a pier in sand with WD Laursen and Touch (1956)

• Different shapes of WD at the pier Melville and Dongol (1992)

Effect of pier position and shape on WD

accumulation (field observations)Diehl (1997), Lyn et al. (2007), Lagasse et al. (2010)

• Squared-nose and semi-circular nose pier

shapes

Wood accumulation at bridges

(flume experiments)• Schematic bridge structures with no piers

Schmocker and Hager (2011)

• WD accumulation at rounded-nose pier Gschnitzer et al. (2013), Lyn et al.(2003)

• WD accumulation at square, multiple column

and wall pier Lagasse et al. (2010)

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The goal

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

TO INVESTIGATE :

• how the pier shape

affects the wood accumulation

formation;

• how the log motion is

altered by bridge piers;

• what are the most critical

piers for the mechanisms of wood

retention

1st step: Flume experiments

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The flumeGEOMETRY:

Length: 5.095 m

Width: 0.30 m

Higth of banks: 0.18 m

Slope: 0.001

HYDRAULIC PARAMETERS:

Froude number: 0.3

Discharge: 4 l/s (steady conditions)

Water level: 8.3 cm

D50= 6.81 mm

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

All measures are in mm

7/18

The dowels

05

10152025303540

0 5 10 15 20 25

% t

ree

s

Length [m]

WOODY

DEBRISCLASS

% of

presence

REAL

SIZES(*)

PHYSICAL

MODEL SIZES

Lwood

(m)

Dwood

(cm)

L dowels

(cm)

Ddowels

(mm)

Small 1 56.6 5-11 5-10 10 2

Medium 2 34 12-16 15-20 17 4

Large 3 9.4 17-20 25-35 20 6

Frequency distribution (percentage) of trees sizes from field measurements (*)

(*) field data taken from riparian vegetation in the Arno river basin

Relative size and the frequency distribution of the dowels

8/18INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

The piersR0: SQUARE - NOSE

Segura Bridge, Alcantara (Spain)

R1: ROUND - NOSE

R2: SHARP - NOSE

Concorde Bridge, Paris (France)

R4: TRAPEZOIDAL - NOSE

Old Bridge, Florence (Italy)

R5: TRUNCATED-OGIVAL CONE

R3: OGIVAL - NOSE

R6: TRIANGULAR NOSE

R7: ROUND + OGIVAL NOSE

Wilson Bridge, Tours (France)

Dattaro Bridge, Parma (Italy)

Margaret Bridge, Budapest (Hungary)

Stone Bridge, Zaragoza (Spain)

Tower Bridge, London (UK)

9/18INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

The tests

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

• Type of transport: uncongested

• Frequency: 1 element/ 5 seconds

• Number of tests: 5

• Type of transport: congested

• Frequency: 20 elements/ 20 seconds

• Number of tests: 10

• Type of transport: congested

• Frequency: 25 elements/ 20 seconds

(20 LWD, 3 MWD, 2 LWD)

• Number of tests: 10

Total number of tests: 175

10/18

The dimensionless blockage index

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

CL = captured logs for a given class

IL = introduced logs in the flume for a given class

CLTOT = total captured logs

ILTOT = total number of logs introduced in the flume

ILSWD= 100

ILMWD= 15

ILLWD= 10

[0-1]

[0-1]

[0-1]

[0-1]

11/18

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS 12/18

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

0.02

0.040.05

0.33

0.460.47

-0.200

0.000

0.200

0.400

0.600

0.800

1.000

0 1 2 3

IAC

size classes of logs

R6

R7

SWD MWD LWD

increase in logs sizes (D,L)

13/18

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

The final step of

congested

transport test

with dowels of

three sizesR0

R1

R2

R3

R4

R5

R6

R7

14/18

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

0.26 0.260.28

0.15

0.26 0.26

0.03

0.35

-0.200

-0.100

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0 1 2 3 4 5 6 7

Global IAC index

15/18

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

0.800

0.120 0.080

0.022 0.040

0.326

0.4600.470

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

0 1 2 3

IAC

size classes of logs

R0

R1

R2

R3

R4

R5

R6

R7SWD MWD LWD

increase in logs sizes (D,L)

CP

16/18

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

• the most critical configuration : round pier with ogival nose (IACgl = 0.35)

• the least critical configuration : triangular nose ( α= 43°) (IACgl = 0.03)

Conclusions 1/2

60° 43°IACgl = 0.28 IACgl = 0.03

• more pointed is the triangular nose less prone to wood accumulation is the pier

17/18

When one of two extremities of a piece of wood encounters

the triangular pier nose, drift rotation is favored;

The logs accumulate on the top of the ogival nose

INTRODUCTION AIM THE PHYSICAL MODEL TESTS RESULTS CONCLUSIONS

• the logs more prone to be ʺcapturedʺ are those in class 3 (Large Woody Debris)

having the smaller frequency

Conclusions 2/2

OBSERVATION !!!

• the dowels used in our tests represent no-rooted and defoliated logs. The

presence of roots and branches could influence the blockage of woody debris at

bridges.

18/18

Thank you for your attentionComments and questions are welcome!!!

@: pinandc@dicea.unifi.it

A special acknowledgment to the laboratory technicians (Mauro Gioli and Muzio Mascherini) and the students

(Gianluca Bigoni, Alessio Bucci, Simone Passerini, Lorenzo Prunecchi, Iacopo Guadagnoli, Giordano Rosadoni,

Michelangelo Torniai, Ilenia Baldini and Giada Artini) for their assistance in flume tests.