BRIDGE SCOUR AND LEVEE OVERTOPPING

Size: px

Start display at page:

Download "BRIDGE SCOUR AND LEVEE OVERTOPPING"

Moses Briggs
5 years ago
Views:

1 BRIDGE SCOUR AND LEVEE OVERTOPPING Jean-Louis BRIAUD President of ISSMGE Professor at Texas A&M University ISSMGE 1 st WEBINAR 23 August Threshold of Optimum Simplicity Einstein said: Things should be made as simple as possible but not one bit simpler than that 2 1

2 Fundamentals Bridge Scour Scour depth predictions Observational method Case history Levee Overtopping Hurricanes Floods Case histories 3 3 Input to an erosion problem Soil (Erodibility Erodibility) Water (Velocity) Geometry (Dimensions) 4 Jean-Louis BRIAUD Texas A&M University 2

3 DEFINITION OF SOIL ERODIBILITY Relationship between the erosion rate and the velocity of the water near the soil-water interface. Relationship between the erosion rate and the shear stress at the soil-water interface. Z f ( ) Constitutive Law fo Soil Erosion Jean-Louis BRIAUD Texas A&M University 5. Constitutive Law for Soil Erosion. Z f ( ) m n p Z c u u u u Mean Net Shear Normal Shear Stress Stress Stress Turbulence Turbulence 6 Jean-Louis BRIAUD Texas A&M University 3

4 Erosion process

5 Erosion process 9 9 FLOW Erosion process FLOW SAND CLAY 5

6 Continuity equation RANS Equations m ( U ),m t Momentum (RANS) Equations g U t mn i U m U i,m R im,m 0 2g i m n m m i im mn i g p,m g U,n, m Energy Equation T C p U t U m, n T m, m U n, m il e lmn m mn u T, m g KT, n, m n mn i j u, nu, m gij g U, mu, n m U m u n Dp Dt i, m u j, n R t Reynolds Stresses Transport Equations ij U m R ij,m Production Diffusion by u m Diffusion by p Viscous Diffusion Pressure Strain Dissipation P P D D D ij ij u ij p ij v ij ij ij D 2e g ij u ( R lmn ( u g m jm mn 2g im U D j,m i u u j ij p ),m il R m ( g R i ( u p' /ρ ) R mn ij,mn ( p' / )( g u i,m u im j,n u jm,m D U jn j,m ij ij ij v i,m g g g ) jl im jm R in ( u u j i,m ) p' /ρ ) ),m

7 7 13 c b Z Z ), ( Scour Rate Equation 13 c b c b c b c b 0 c Z,, ), ( b W V U q n q ; 14 CONTRACTION RATIO = FLOW

8 CONTRACTION RATIO = FLOW 16 8

10 Testing for erodibility (EFA) EFA (Erosion Function Apparatus) Testing for erodibility (EFA) FINE SAND FLOW 10

11 LOW PI PREPARED CLAY FLOW FISSURED SILTY CLAY FROM ACTUAL BRIDGE SITE FLOW 11

12 FISSURED SILTY CLAY FROM ACTUAL BRIDGE SITE FLOW FISSURED SILTY CLAY FROM ACTUAL BRIDGE SITE FLOW 12

13 FISSURED SILTY CLAY FROM ACTUAL BRIDGE SITE FLOW Testing for erodibility (EFA) Erosion function for a fine sand 13

14 Testing for erodibility (EFA) Erosion function for a low PI clay EROSION FUNCTION APPARATUS TEST Erosion Rate (mm/hr) Very High Erodibility I Fine Sand -Non-plastic Silt High Erodibility II -Medium Sand -Low Plasticity Silt Medium Erodibility III -Jointed Rock (Spacing < 30 mm) -Fine Gravel Low Erodibility -Coarse Sand 1000 IV SP SM - Increase in Compaction (well graded soils) - Increase in Density - Increase in Water Salinity (clay) ML MH CL -High Plasticity Silt -Low Plasticity Clay -All fissured Clays CH Rock -Jointed Rock ( mm Spacing) -Cobbles -Coarse Gravel -High Plasticity Clay Very Low Erodibility V -Jointed Rock ( mm Spacing) -Riprap Velocity (m/s) Non-Erosive -Intact Rock VI -Jointed Rock (Spacing > 1500 mm) 14

15 Erosion Classification (Shear Stress) Erosion Rate (mm/hr) Very High Erodibility I Fine Sand -Non-plastic Silt High Erodibility II Medium Erodibility III -Medium Sand -Jointed Rock -Low Plasticity Silt (Spacing < 30 mm) -Fine Gravel Low Erodibility Coarse Sand IV High Plasticity Silt -Low Plasticity Clay -All fissured Clays - Increase in Compaction (well graded soils) - Increase in Density - Increase in Water Salinity (clay) SM SP ML MH CL CH -Jointed Rock ( mm Spacing) -Cobbles -Coarse Gravel -High Plasticity Clay Rock -Riprap Very Low Erodibility V -Jointed Rock ( mm Spacing) Non-Erosive -Intact Rock -Jointed Rock VI (Spacing > 1500 mm) Shear Stress (Pa) CRITICAL VELOCITY vs GRAIN SIZE INTACT ROCK CLAY SILT SAND GRAVEL RIP-RAP & JOINTED ROCK Critical Velocity, V c (m/s) V c = 0.03 (D 50 ) -1 US Army Corps of Engineers EM V c = 0.1 (D 50 ) -0.2 V c = 0.35 (D 50 ) E-06 1E Mean Grain Size, D 50 (mm) Joint Spacing for Jointed Rock 15

CRITICAL SHEAR STRESS vs GRAIN SIZE INTACT ROCK CLAY SILT SAND

2 ) 10000 1000 100 10 1 US Army Corps of Engineers EM 1601 c = 0.

4 Shields (1936) 0.01 1E-06 1E-05 0.0001 0.

01 0.1 1 10 100 1000 10000 Mean Grain Size, D 50 (mm) Joint Spacing

16 CRITICAL SHEAR STRESS vs GRAIN SIZE INTACT ROCK CLAY SILT SAND GRAVEL RIP-RAP & JOINTED ROCK Critical Shear Stress, c (N/m 2 ) US Army Corps of Engineers EM 1601 c = (D 50 ) -2 c = D Curve proposed by c = 0.05 (D 50 ) -0.4 Shields (1936) E-06 1E Mean Grain Size, D 50 (mm) Joint Spacing for Jointed Rock 31 POCKET ERODOMETER PET test result = Depth of hole in mm after 20 squirts at 8 m/s 32 $0.49 at WalMart Jean-Louis BRIAUD Texas A&M University 16

17 Velocity Calibration v 0x x 2H g 33 Jean-Louis BRIAUD Texas A&M University 34 Jean-Louis BRIAUD Texas A&M University 17

18 POCKET ERODOMETER TEST 35 Erodibility depends on soil properties 1. Soil water content 2. Soil unit weight 3. Soil plasticity index 4. Soil undrained shear str. 5. Soil void ratio 6. Soil swell 7. Soil mean grain size 8. Soil percent passding # Soil clay minerals 10. Soil dispersion i ratio 11. Soil cation exchange cap 12. Soil sodium absorption rat 13. Soil ph 14. Soil temperature 15. Water temperature 16. Water salinity 17. Water ph 36 Jean-Louis BRIAUD Texas A&M University 18

NO SIMPLE CORRELATION! CSS vs.#200 CSS vs. Su 25.00 45.00 40.00 20.00 35.00 30.00 15.00 10.00 CSS(Pa) 25.00 20.00 R 2 = 0.1093 15.00 5.00 R 2 =0 0.1306 10.00 5.00 0.00 0.00 20.00 40.00 60.00 80.

4 m/s 100000 10000 1000 Erosion Rate 100 (mm/hr) 10 1 Very High Erodibility I High Erodibility II Medium Erodibility III Low Erodibility IV Very Low Erodibility V 0.1 0.1 1.0 10.0 100.0 Velocity (m/s) 100000 10000 Erosion 1000 Rate (mm/hr) 100 10 1 0.

19 NO SIMPLE CORRELATION! CSS vs.#200 CSS vs. Su CSS(Pa) R 2 = R 2 = #200(%) Su(kPa) 37 Jean-Louis BRIAUD Texas A&M University EFA test on Creamy Peanut Butter S u = 1.8 kpa V c = 1.4 m/s Erosion Rate 100 (mm/hr) 10 1 Very High Erodibility I High Erodibility II Medium Erodibility III Low Erodibility IV Very Low Erodibility V Velocity (m/s) Erosion 1000 Rate (mm/hr) Very High Erodibility I High Erodibility II Medium Erodibility III Low Erodibility IV Very Low Erodibility V Shear Stress (Pa) 38 Jean-Louis BRIAUD Texas A&M University 19

20 Shear Stress Applied by Water dz 39 Jean-Louis BRIAUD Texas A&M University 40 Jean-Louis BRIAUD Texas A&M University 20

21 41 Jean-Louis BRIAUD Texas A&M University Flow Hydrograph 42 Jean-Louis BRIAUD Texas A&M University 21

22 Velocity & Water Depth Hydrograph 43 Jean-Louis BRIAUD Texas A&M University Obtaining a design flood value 44 Jean-Louis BRIAUD Texas A&M University 22

NIAGARA FALLS 11000 m of lateral erosion from Lake Ontario

1 mm/hr 45 Niagara Falls 1841 Lake Erie Lake Ontario

com/~falls/origins.html http://www.samizdat.qc.

htm Jean-Louis BRIAUD Texas A&M University GRAND CANYON

23 NIAGARA FALLS m of lateral erosion from Lake Ontario towards Lake Erie in years or 0.1 mm/hr 45 Niagara Falls 1841 Lake Erie Lake Ontario Niagara River From Google Earth Jean-Louis BRIAUD Texas A&M University GRAND CANYON 1600 m of vertical erosion by the Colorado River in 10 Million years or mm/hr 46 Jean-Louis BRIAUD Texas A&M University 23

24 Fundamentals Bridge Scour Scour depth predictions Observational method Case history Levee Overtopping Hurricanes Floods Case histories 47 FOUNDATION DESIGN 48 J.-L. Briaud, Texas A&M University 24

1000 Mike Sullivan, NYDOT, 2005 lures from 502 Total)

300 200 100 0 60% 50% 40% 30% 20% 10% 0% Construction

Misc. Percen nt Overload Collision Hydraulic Cause

25 1000 Mike Sullivan, NYDOT, 2005 lures from 502 Total) Number of Fail 1966 to 2005 ( % 50% 40% 30% 20% 10% 0% Construction Concrete Deterioration Earthquake Natural Steel Fire Misc. Percen nt Overload Collision Hydraulic Cause Jean-Louis Briaud 50 Jean-Louis BRIAUD Texas A&M University 25

26 51 Hatchie River Bridge, Tennessee Courtesy of the University of Kentucky at Louisville 52 26

Tie the two decks with cables Increase the support length Austin 59

30 Tie the two decks with cables Increase the support length Austin Scour Components Jean-Louis Briaud Texas A&M University 60 30

31 Scour Components Jean-Louis Briaud Texas A&M University 61 Scour types C L y s(abut) Applies Probable Flood Level y s(cont) Applies y s(abut) y s(pier) y s(cont) Normal Water Level Where, y s(abut) is Abutment Scour Depth y s(cont) is Contraction Scour Depth y s(pier) is Pier Scour Depth 31

32 Historic Meandering River Surveys 63 Mississippi River Meander Belt 64 32

33 Problem Constant flood velocity = 3m/s Flood duration = 48 hours Pier diameter = 2m Water depth = 5m What is the depth of scour after the flood? Solution HEC-18 CLAY Method z (mm/hr) Results of EFA tests t gave z vs Maximum hydraulic shear stress around pier: max 0.094V N / m log Re The initial rate of scour is z 30 mm/ hr critical velocity of soil is Vc 2.2 ( m/ s) The maximum depth of scour y s( Pier ) is: 0.7 y y 2.2 a 2.6 Fr Fr 5.2 m s ( Pier ) ( pier ) c ( pier ) 5. The equation for the () s( Pier) t curve is t 48( hrs) ys( Pier) ( t) 1127mm 1 t 1 48( hrs) z i ys( Pier) Maximum flood lasts 48 hours, therefore ys( Pier)( t) 1127mm or 21.7% of y s( Pier) z (mm/hr) y () 4000 s t (mm) 3000 z i 30 mm / hr max ( N / m ) 10 0 Vc 2.19( m/ sec) V ( m / sec) y 5191mm s( Pier) 2000 ys( Pier) 48hrs 1127mm T ( hrs) Problem: Solution: Constant flood velocity = 3m/s Flood duration = 48 hours Pier diameter = 2m Water depth = 5m What is the depth of scour after the flood? SRICOS Method 1. Results of EFA tests gave the z vs curve shown 2. Maximum hydraulic shear stress around the pier is: max 0.094V1 log Re N / m 3 2 log The initial rate of scour z is read on the EFA curve at max. z 30 mm / hr, and the critical velocity of soil is Vc 2.19( m/ s) 4. The maximum depth of scour y s( Pier) is: 0.7 y 2.2 a 2.6 Fr( Frc s( Pier pier ( pier ) ) ) m 5. The equation for the y () ( ) t curve is s( Pier) s Pier t 48( hrs) ys( Pier) ( t) 1127mm 1 t 1 48( hrs) z y i 6. Maximum flood lasts 48 hours, therefore y ( ) 1127 s( Pier) t mm or 21.7% of y s( Pier) z (mm/hr) z (mm/hr) y () 4000 s t (mm) z i 30 mm / hr Vc max 2.19( m/ sec) 2 ( N / m ) V ( m /sec) y 5191mm s( Pier) y 48hrs mm s( Pier) T ( hrs) 66 33

34 12000 W oodrow W ilson Bridge Hydrography Discharge (m 3 /sec) D Time (year) 7000 Scour D epth V s Tim e h (mm) Scour Depth T im e (y e a r ) 67 Jean-Louis Briaud-Texas A&M University Scour Depth versus Time 60 Scour Depth (mm) Z i Z max Measurement Hyperbola Hyperbola Model: zt () 1 z i t t z max Time(hr) 68 Jean-Louis Briaud-Texas A&M University 34

1.5 1.25 1 Y/B 0.75 0.5 max( Pier) 0.25 max 0-1.5-1 -0.5 0 0.5 1 1.5 0.094V 1 2 X/B 1 1 log Re 10 WEI (1997) 0.03 U 2 max 0.025 0.02 max =f(re) U 2 0.015 0.01 0.

35 Y/B max( Pier) 0.25 max V 1 2 X/B 1 1 log Re 10 WEI (1997) 0.03 U 2 max max =f(re) U Re 69 Jean-Louis Briaud-Texas A&M University Time dependent predictions z (mm/hr) 600 z i Pa c max (Pa) 70 35

36 SRICOS - EFA Scour in constant flow V 60 ( m/ s) ys() t 60 (mm) Time ( hrs). Z i Max. scour Z max Constant flow. Z i is obtained from t max Scour development Hyperbolic shape Time ( hrs) Scour depth as a function of time (hyperbolic model) t ys () t 1 t z y i s Max. Scour depth Erosion function Max. shear stress 36

Problem Constant flood velocity = 3m/s Flood duration = 48 hours Pier diameter = 2m Water depth = 5m What is the depth of scour after the flood? 73 Solution HEC-18 CLAY Method z (mm/hr) 30 1.

The initial rate of scour is z 30 mm/ hr critical velocity of soil is Vc 2.2 ( m/ s) 20 4. The maximum depth of scour y s( Pier ) is: 0.7 y y 2.2 a 2.6 Fr Fr 5.2 m s ( Pier ) ( pier ) c ( pier ) 5.

37 Problem Constant flood velocity = 3m/s Flood duration = 48 hours Pier diameter = 2m Water depth = 5m What is the depth of scour after the flood? 73 Solution HEC-18 CLAY Method z (mm/hr) Results of EFA tests t gave z vs Maximum hydraulic shear stress around pier: max 0.094V N / m log Re The initial rate of scour is z 30 mm/ hr critical velocity of soil is Vc 2.2 ( m/ s) The maximum depth of scour y s( Pier ) is: 0.7 y y 2.2 a 2.6 Fr Fr 5.2 m s ( Pier ) ( pier ) c ( pier ) 5. The equation for the () s( Pier) t curve is t 48( hrs) ys( Pier) ( t) 1127mm 1 t 1 48( hrs) z i ys( Pier) Maximum flood lasts 48 hours, therefore ys( Pier)( t) 1127mm or 21.7% of y s( Pier) z (mm/hr) y () 4000 s t (mm) z i 30 mm / hr max ( N / m ) 10 0 Vc 2.19( m/ sec) V ( m / sec) y 5191mm s( Pier) ys( Pier) 48hrs 1127mm T ( hrs) 74 J.-L. Briaud, Texas A&M University 37

38 75 J.-L. Briaud, Texas A&M University 76 J.-L. Briaud, Texas A&M University 38

39 77 J.-L. Briaud, Texas A&M University 78 J.-L. Briaud, Texas A&M University 39

40 79 J.-L. Briaud, Texas A&M University 80 J.-L. Briaud, Texas A&M University 40

41 81 J.-L. Briaud, Texas A&M University 82 J.-L. Briaud, Texas A&M University 41

42 60 Scour Depth (m mm) Z i Z max 10 Measurem ent Hyperbola Time(hr) 83 Jean-Louis Briaud-Texas A&M University y Maximum pier scour (Oh, 2009) s( Pier) a ' where, K K K K 2.6Fr Fr w 1 L sp ( pier) c( pier) 0.33 y1 y1 0.89, for 1.43 Kw a' a' 1.0, else 1.0, for 30 K1 Value in following Table, else KL 1.0, for whole range of L/ a 0.91 S S 2.9, for 3.42 K sp a' a' , else K 1 Shape of pier nose Shape of pier nose Square nose 1.1 Circular cylinder 1.0 Round nose 1.0 Sharp nose 0.9 K

43 Max. shear stress for pier scour (Nurtjahyo, 2003) Cylindrical pier in deep water 0094V max log Re 10 V1 a where, Re is the kinematic viscosity of water (10 6 m 2 /s at 20 o C) V1 a y Complex pier max ksh k kw ksp V1 log Re 10 where, k sh kw 116 L 4 a e 4 y a e k ksp S a e Maximum pier scour (Oh, 2009) 6 5 y s(pier) /a 4 3 y = x R² = (2.6Fr (pier) Fr c(pier) ) 0.7 y/a= 16 y/a = 6.4 y/a = 6.6 y/a=5.33 y/a = 3.4 y/a = 2.13 y/a = 2.0 y/a = 1.67 y/a =

44 Maximum and uniform contraction scour 87 Jean-Louis Briaud Texas A&M University 44

45 B 2 /B 1 = 0.75 Jean-Louis Briaud Texas A&M University B 2 /B 1 = 0.5 Jean-Louis Briaud Texas A&M University 45

5 y s(cont) /y m1 2 1.5 1 0.5 y = 0.9985x 0.

46 B 2 /B 1 = 0.25 Jean-Louis Briaud Texas A&M University Maximum and uniform contraction scour (Oh, 2009) y s( Cont) y m Fr Fr m2 mc 2.5 y s(cont) /y m y = x R² = Li (Long contraction) (2002) WW in rect. 0 Best Fit Frm2 Frmc 92 46

47 Max. shear stress for contraction scour (Nurtjahyo, 2003) Max. shear stress without contraction (Munson et al., 1990) max( Cont ) 1 h gn V R Max. shear stress with contraction max( Cont) kk R Wakk wgnvr 1 h where, A k R A 1.75 kw k 1.5 wa 1.0 for all conditions 2 k Wa 1.0,for 0.35 L' left L' right 2 W a W a , otherwise L' left L' right L' left L' right Maximum abutment scour (Briaud et al. 2009) 94 47

48 Clay Installation Jean-Louis Briaud Texas A&M University 95 View of Test Section Jean-Louis Briaud Texas A&M University 96 48

49 97 Maximum abutment scour (Briaud et al. 2009) Maximum abutment scour (Briaud et al. 2009) 98 49

50 Flow Direction Jean-Louis Briaud Texas A&M University 99 Maximum abutment scour (Briaud et al. 2009)

51 Maximum abutment scour (Briaud et al. 2009) y y s(abut) / y f1 s( Abut) y f K K K K K Fr Fr 1 2 L G Re f 2 fc y = 1.000x R² = Frf 2 Frfc

103 Max. Shear stress for abutment scour (Briaud et al. 2009) 5.93k k k k k k k 2.1V Re 2 0.

45 1 where, k k Cr Fr q 2 3.65 2.91 q 1 k sh L' 0.85 W a 2.07Fr 0.8 for Fr > 0.1 1.0 for Fr 0.1 0.

0 for L ' f L / yf 2 ' ' 0.6( Lf L) / yf 1.2 for 2 ( Lf L) / yf 0 kl ' ' 1.2( L f L) / y f 1.

52 103 Max. Shear stress for abutment scour (Briaud et al. 2009) 5.93k k k k k k k 2.1V Re max( Abut) Cr sh Fr s sk L o k k k k k k k V Re Cr sh Fr s sk L o where, k k Cr Fr q q 1 k sh L' 0.85 W a 2.07Fr 0.8 for Fr > for Fr k s ksk vertical-wall abutment 0.65 wing-wall abutment 0.58 spill-through abutment 1.0 for L ' f L / yf 2 ' ' 0.6( Lf L) / yf 1.2 for 2 ( Lf L) / yf 0 kl ' ' 1.2( L f L) / y f 1.2 for 0 ( L f L) / y f 1 ' 1.0 for 1 ( Lf L) / yf 0.92 d1 / ddeck 1.0 for d1 / ddeck ko 0.21 d1 / ddeck 1.27 d1 / ddeck 2.97 for 1.0 d1 / ddeck for 3.0 d1 / ddeck

53 2 1 Max. Friction Coefficient C V f _ VW max / C f _ VW 21. Re 045. VW abutment results VW abutment Eq. 1.0E E E E+07 V1 Wa Re 8.0 Velocity influence in same geometry 2.1V Re where, V W is the kinematic viscosity of Water (10 6 m 2 /s at 20 o C) 1 a Re k Cr k q2 Cr Contraction influence (K Cr ) q 1 q q Unit discharge ratio, (q 2 /q 1 ) where, q1 V1 y1 q V y A / A W oodrow W ilson Bridge Hydrography Discharge (m 3 /sec) D Time (year) 7000 Scour D epth V s Tim e h (mm) Scour Depth T im e (y e a r ) 106 Jean-Louis Briaud-Texas A&M University 53

54 Scour due to a sequence of two flood events V ( / ) 60 m s50 2 V V 1 t t 1 2 Sequent flood 0 ys() t 60 (mm) Time ( hrs) t t 1 2 Scour development 10 0 * t Time ( hrs) Scour of a two-layer soil v ys() t 60 (mm) y Layer 1 (Hard) t Time ( hrs) v ys() t 60 (mm) y 1 Layer 2 (Soft) t * Time ( hrs) v Layer 1 (Hard) Layer 2 (Soft) y 1 ys() t 60 (mm) y t * t Time ( hrs) 54

55 1 ' ' ' 0.91 ' a ' a ' 2 ' ' f f f f ' ' f f f f ' ' f f f1 f1 s( Abut ) L G p f 2 f 2 fc f 1 f 2 1 f ' ' a ' f f q q L q a e q L W W W L L 2.07Fr 0.8 Fr>0.1 y 4 a 1.0 Fr e 1.0 for VW S 1.1 a 1 5e 0.65 for WW and ST 1.0 L L / y for rectangular nose 0.6( L L) / y ( L L) / y for round nose & cylinder 1.2( L L) / y ( L L) / y 1 y scont ( ) ( L L) / y y y Fr2( Cont ) Frmc 0.89, for < 1.43 y a a m d / h1, if d / h , for otherwise max( Cont ) kk R Wakk wnvr 1 h 1.83 d / h 3.76 d / h2.97, if 0.33 d / h1.0 S S 1.0, if 1.0 d / h 2.9, for < 3.2 a a 1.0, for otherwise 1.22 for VW 1.0 for WW 0.73 for ST ys ( Pier ) K1 Ksp KL Kw Fr( pier ) Frc ( pier ) a' max( pier ) kk w shkspk 0.094V log Re for otherwise L L L L <1.5 y y 1.0 otherwise y y Re K K K K K Fr Fr max( Abut ) 12.45kCrkshkFrksksk klkov1 Re Hydrograph (Add 500year flood) Streamflow(m 3 /s) Time (Year) Scour Depth Vs. Time (Add 500year flood) 12 Scour Dep epth (m) Time (Year) 110 Jean-Louis Briaud-Texas A&M University 55

56 What is the frequency of occurrence and probability of exceedance for Q 100 = 12,629 m 3 /s, Q 500 = 16,639 m 3 /s, and L t = 75 yrs? Frequency of Occurrence vs. Scour Depth Probability of exceedance vs. Scour Depth 112 J.-L. Briaud, Texas A&M University 56

57 Woodrow Wilson Bridge on I-495 in Washington D.C. 113 Probably of Exceedance PoE yr 53% PoE, v 100 = 28* 2.8 m/s 500 yr 13.9% PoE, v 500 = 3.25* m/s yr 0.75% PoE, v = 3.95* m/s * Example for Woodrow Wilson Bridge for 75 year design life. Structural Eng. operate at a Prob. of Exceedance of 0.1%? Geotechnical Eng. operate at a Prob. of Exceedance of 1%? Hydraulic Eng. operate at a Prob. of Exceedance of 10%? 57

58 VERIFICATION Pre edicted Scour Depth (cm m) SRICOS-EFA HEC M easured Scour Depth (cm) 115 Jean-Louis Briaud Texas A&M University Verification Predcition (m) Predcition (m) Measurement (m) Measurement (m) Prediction vs. Froehlich s pier scour database (1988) Prediction vs. Muller and Lander s pier scour database (1996)

59 Verification Uniform contraction scour Prediction (mm m) Komura (1966) Gill (1981) Webby (1984) Lim (1993) Measurement (mm) Prediction vs. Gill s uniform contraction scour database (1981), Komura (1966), Webby (1984), Lim (1993) 117 Verification Maximum abutment scour I Prediction (m) Measurement (m) W.W. (1982) Kwan W.W. (1988) Tey W.W. (1984) Wong Liu S.T. (1961) Tey S.T. (1984) Wong S.T. (1982) Tey V.W. (1984) Liu V.W. (1961) Gill V.W. (1972) Garde V.W. (1961) Kwan V.W. (1984) Prediction (m) Measurement (m) V.W. (Long) V.W. (Inter) V.W. (Short) S.T. (Inter) S.T. (Short) W.W. (Inter) Prediction vs. Froehlich s abutment scour database (1981) Prediction vs. Sturm s abutment scour database (2004)

60 Verification Maximum abutment scour II Prediction (m) ST WW Measurement (m) ) Prediction (m) Q100 Historic data Measurement (m) Prediction vs. Ettema et al. s abutment scour database (2008) Prediction vs. Benedict and Caldwell s abutment scour database (2006) 119 Fundamentals Bridge Scour Scour depth predictions Observational method Case history Levee Overtopping Hurricanes Floods Case histories

61 Scour Critical Bridge means Foundation is unstable for calculated and/or observed scour conditions / in the U.S. 600 / in Texas Jean-Louis BRIAUD 121 OBSERVATION METHOD FOR BRIDGE SCOUR Step 1: Observe maximum scour depth = Zmo Step 2: Find out the maximum flood the bridge has been subjected to = Vmo Step 3: Extrapolate field measurements to predict future scour depth Zfut / Zmo = F (Vfut / Vmo) Step 4: Compare future scour depth to foundation depth Zfut < Zfound / 2 Jean-Louis BRIAUD

62 Drawbacks Requires a good network of flow gages and rain gages Cannot be used for new bridges Estimate in filling (USGS has found that it was rare and measured from 2 to 5 ft) Jean-Louis BRIAUD 123 Advantages No need for erosion testing Actual soil Actual flow history Actual geometry Based on observed measurements Jean-Louis BRIAUD

63 Observation Method for Bridge Scour Step 1: Observe maximum scour depth = Zmo Step 2: Find out the maximum flood the bridge has been subjected to = Vmo Step 3: Extrapolates field measurements to predict future scour depth Zfut/Zmo = F (Vfut/Vmo) Step 4: Compare future scour depth to foundation depth Zfut < Zfound/2 Jean-Louis BRIAUD 125 Step 1: Observe maximum scour depth = Zmo Jean-Louis BRIAUD

Observation Method for Bridge Scour Step 1: Observe maximum scour depth = Zmo Step 2: Find out the maximum flood the bridge has been subjected to = Vmo Step 3: Extrapolates field measurements to

64 Observation Method for Bridge Scour Step 1: Observe maximum scour depth = Zmo Step 2: Find out the maximum flood the bridge has been subjected to = Vmo Step 3: Extrapolates field measurements to predict future scour depth Zfut/Zmo = F (Vfut/Vmo) Step 4: Compare future scour depth to foundation depth Zfut < Zfound/2 Jean-Louis BRIAUD 127 Step 2: Find out the maximum flood the bridge has been subjected to = Vmo 930 Flow Gages in Texas Jean-Louis BRIAUD

65 Step 2: Find out the maximum flood the bridge has been subjected to = Vmo Maximum flood analysis Jean-Louis BRIAUD 129 Step 2: Find out the maximum flood the bridge has been subjected to = Vmo Maximum RI map between 1970 and 2005 Automated with TAMU- FLOOD software (free on internet) Jean-Louis BRIAUD

Step 2: Find out the maximum flood the bridge has been subjected to = Vmo Maximum RI map between 1920 and 2005 Automated with TAMU- FLOOD software (free on internet) Jean-Louis BRIAUD 131 Observation

66 Step 2: Find out the maximum flood the bridge has been subjected to = Vmo Maximum RI map between 1920 and 2005 Automated with TAMU- FLOOD software (free on internet) Jean-Louis BRIAUD 131 Observation Method for Bridge Scour Step 1: Observe maximum scour depth = Zmo Step 2: Find out the maximum flood the bridge has been subjected to = Vmo Step 3: Extrapolates field measurements to predict future scour depth Zfut/Zmo = F (Vfut/Vmo) Step 4: Compare future scour depth to foundation depth Zfut < Zfound/2 Jean-Louis BRIAUD

67 Step 3: Extrapolates field measurements to predict future depth Zfut/Zmo = F (Vfut/Vmo) Known = Zmo and Vmo Choose Vfut Obtain Zfut from charts Zfut / Zmo = F (Vfut / Vmo) Jean-Louis BRIAUD 133 Step 3: Extrapolates field measurements to predict future depth Zfut/Zmo = F (Vfut/Vmo) The Z-Future Charts were developed by performing a large number (~350,000) of HEC-18 Clay simulations using Varying pier & contraction scour geometry Varying soil conditions Varying velocities Varying age of the bridge Jean-Louis BRIAUD

68 Erosion Rate (mm/hr) Very High Erodibility I Fine Sand -Non-plastic Silt High Erodibility II -Medium Sand -Low Plasticity Silt Medium Erodibility III -Jointed Rock (Spacing < 30 mm) -Fine Gravel Low Erodibility -Coarse Sand 1000 IV SP SM - Increase in Compaction (well graded soils) - Increase in Density - Increase in Water Salinity (clay) ML MH CL -High Plasticity Silt -Low Plasticity Clay -All fissured Clays CH Rock -Jointed Rock ( mm Spacing) -Cobbles -Coarse Gravel -High Plasticity Clay Very Low Erodibility V -Jointed Rock ( mm Spacing) -Riprap Velocity (m/s) Non-Erosive -Intact Rock VI -Jointed Rock (Spacing > 1500 mm) 135 Step 3: Extrapolates field measurements to predict future scour depth Zfut/Zmo = Vfut/Vmo 2.8 Z fut /Z mo Category III Materials Upstream Water Depth (H 1 1) ): 5 m to 20 m Contraction Ratio (R c ) : 0.5 to 0.9 Critical Velocity (V c ) : 0.5 m/s Pier Diameter (D) : 0.1m to 1.0 m t hyd = 25 years V fut /V mo 2.0 Jean-Louis BRIAUD

69 Step 3: Extrapolates field measurements to predict future scour depth Zfut/Zmo = Vfut/Vmo Jean-Louis BRIAUD 137 Observation Method for Bridge Scour Step 1: Observe maximum scour depth = Zmo Step 2: Find out the maximum flood the bridge has been subjected to = Vmo Step 3: Extrapolates field measurements to predict future scour depth Zfut/Zmo = F (Vfut/Vmo) Step 4: Compare future scour depth to foundation depth Zfut < Zfound / 2 Jean-Louis BRIAUD

70 Step 4: Compare future scour depth to foundation depth Zfut < Zfound / 2 Jean-Louis BRIAUD 139 VERIFICATION t Predicted (ft) Z fut Z fut Measured (ft) Jean-Louis BRIAUD

71 APPLICATION TO SCOUR CRITICAL BRIDGES 15 bridges selected (12 scour critical, 3 stable) 6 scour critical bridges out of the 12 found stable by the observation method 3 stable bridges found stable by the observation method 6 of 12 bridges originally classified scour critical were found stable by the observation method Jean-Louis BRIAUD 141 Fundamentals Bridge Scour Scour depth predictions Observational method Case history Levee Overtopping Hurricanes Floods Case histories

72 Woodrow Wilson Bridge and Pier Scour 143 Jean-Louis BRIAUD Texas A&M University 144 Jean-Louis BRIAUD Texas A&M University 72

73 New Woodrow Wilson Bridge 145 Jean-Louis BRIAUD Texas A&M University Jean-Louis Briaud-Texas A&M University

74 147 Jean-Louis BRIAUD Texas A&M University Bascule Pier Layout (M1) 148 Arch Rib Direction of Flow EL. 4 m (500 yr) EL. 3 m (100 yr) Pedestal EL. 0.6 m (Ave.) 58.1 m 5.9 m EL m (River Bottom) 1.8 m Dia. open ended steel pipe pile 39.2 m Estimated Tip EL m 26.5 m Jean-Louis BRIAUD Texas A&M University 74

75 Testing for erodibility (EFA) EFA (Erosion Function Apparatus) Flow vs. Time Stream flow (m 3 /s) Time (Year) Pier scour depth vs. Time (m) Scour Depth Time (Year) 75

Comparison of Scour Predictions Bascule Pier M1 (500yr Flood) 151 35.0 30.0 25.0 Scour Depth (m 20.0 15.

0 HEC-18 Sand (Pile Width) HEC-18 Sand (Pile Cap) Salim- Jones HEC-18 Clay (Texas A&M) Erodibility Index

76 Comparison of Scour Predictions Bascule Pier M1 (500yr Flood) Scour Depth (m HEC-18 Sand (Pile Width) HEC-18 Sand (Pile Cap) Salim- Jones HEC-18 Clay (Texas A&M) Erodibility Index Large Scale Flume Test Small Scale Flume Test Selected Scour Jean-Louis BRIAUD Texas A&M University TO SCALE152 NEW BRIDGE WITH STRATIGRAPHY NOT TO SCALE Jean-Louis BRIAUD Texas A&M University 76

Load 618 kn 12000 kn EL. 4 m (500 yr) EL.

) River Alluvial Soil 5.9 m 13.0 m EL. -10.

77 Pile for Bascule Pier (M1) 153 M1: Earthquake M2: Vessel Collision M3~M10: Wind Load 618 kn kn EL. 4 m (500 yr) EL. 3 m (100 yr) EL. 0.6m (Ave.) River Alluvial Soil 5.9 m 13.0 m EL m (River Bottom) Glacial Sand 100 yr scour depth 45.1 m Cretaceous Clay Open Ended Steel Pipe Pile (D = 1.8 m, L = 64 m) EL m (Estimated Pile Tip) Jean-Louis BRIAUD Texas A&M University Static Load Test 154 Jean-Louis BRIAUD Texas A&M University 77

78 155 Statnamic Load Test Jean-Louis BRIAUD Texas A&M University 156 Jean-Louis BRIAUD Texas A&M University 78

79 ITEM Total cost of the bridge project with approaches Cost of the bridge between abutments COST 2000 Million Dollars 625 Million Dollars Cost of foundation 125 Milllion Dollars Length of piles with 20 m scour hole Length of piles with 10 m scour hole Potential saving Instrumentation would have cost about 60 meters 50 meters 22 Million Dollars 0.5 Million Dollars 157 Conclusion The SRICOS-EFA method is a new method top predict bridge scour depth based on large flume tests, advanced anced numerical simulations, and verification at full scale and against several databases. This method is less conservative than the current method because it takes the soil erosion resistance and the time effect into account. The software is free on Briaud s web site (Google Briaud) including examples and user s guide

Hurricanes Floods Case histories 159 159 Overtopping

80 Fundamentals Bridge Scour Scour depth predictions Observational method Case history Levee Overtopping Hurricanes Floods Case histories Overtopping Erosion Levee Failure Modes (Martindale, 2009) 80

81 Overtopping Erosion 161 Floodwall Case 161 (Ellis Lucia/The Times Picayune) 162 Overtopping Erosion Dec1954 Maade Dike (Germany North Coast) 81

82 Dec1954 Maade Dike (Germany North Coast) Dec1954 Maade Dike (Germany North Coast) 82

83 Dec1954 Maade Dike (Germany North Coast) Dec1954 Maade Dike (Germany North Coast) 83

84 Dec1954 Maade Dike (Germany North Coast) Dec1954 Maade Dike (Germany North Coast) 84

85 Dec1954 Maade Dike (Germany North Coast) Dec1954 Maade Dike (Germany North Coast) 85

86 Erosion Classification (Shear Stress) Erosion Rate (mm/hr) Very High Erodibility I Fine Sand -Non-plastic Silt High Erodibility II Medium Erodibility III -Medium Sand -Jointed Rock -Low Plasticity Silt (Spacing < 30 mm) -Fine Gravel Low Erodibility Coarse Sand IV High Plasticity Silt -Low Plasticity Clay -All fissured Clays - Increase in Compaction (well graded soils) - Increase in Density - Increase in Water Salinity (clay) SM SP ML MH CL CH -Jointed Rock ( mm Spacing) -Cobbles -Coarse Gravel -High Plasticity Clay Rock -Riprap Very Low Erodibility V -Jointed Rock ( mm Spacing) Non-Erosive -Intact Rock -Jointed Rock VI (Spacing > 1500 mm) Shear Stress (Pa) Fundamentals Bridge Scour Scour depth predictions Observational method Case histories Levee Overtopping Hurricanes Floods Case histories

87 Overtopping Erosion Overtopping During Hurricane Events Hurricane Katrina New Orleans, Louisiana Overtopping Erosion The Event 250 miles in diameter 25 miles per hour 6000 wave cycles Storm surge 10 hours Duration over a bridge or levee = 10 hours

88 Overtopping Erosion Storm Surge 8.5 m 4.6 m 3.0 m Overtopping Erosion Storm Surge

89 Overtopping Erosion Overtopping Erosion

90 Overtopping Erosion Overtopping Erosion

91 Overtopping Erosion Overtopping Erosion

92 Overtopping Erosion Overtopping Erosion The Investigation

93 Overtopping Erosion EFA Test Results Erosion Rate vs. Water Velocity Erosion Rate (mm/hr) Very High Erodibility I High Erodibility II Medium Erodibility III Low Erodibility IV 10 Very Low Erodibility V 1 Non- Erosive 0.1 VI Velocity (m/s) S1-B1-(0-2ft)-TW S1-B1-(2-4ft)-SW S2-B1-(0-2ft)-TW S2-B1-(2-4ft)-SW S3-B1-(2-4ft)-SW S3-B2-(0-2ft)-SW S3-B3-(0-1ft)-SW S4-(0-0.5ft)-LC-SW S4-(0-0.5ft)-HC-SW S5-(0-0.5ft)-LT-SW S6-(0-0.5ft)-LC-SW S7-B1-(0-2ft)-TW S7-B1-(2-4ft)-SW S8-B1-(0-2ft)-TW S8-B1-(2-4ft)-L1-SW S8-B1-(2-4ft)-L2-SW S11-(0-0.5ft)-LC-TW S11-(0-0.5ft)-HC-TW S12-B1-(0-2ft)-TW S12-B1-(2-4ft)-SW S15-Canal Side-(0-0.5ft)-LC-SW S15-CanalSide-(0-0.5ft)-HC-SW S15-Levee Crown-(0-0.5ft)-LT-SW S15-Levee Crown-( ft)-LT-SW Overtopping Erosion Levees Failed and Not Failed Erosion Rate (mm/hr) Note: - Solid circles = levee breaches - Empty circles = no levee damage Very High Erodibility I High Erodibility II Medium Erodibility III 1000 Low 100 Erodibility IV 10 Very Low Erodibility V 1 Non-Erosive VI Velocity (m/s) S2-B1-(0-2ft)-TW S2-B1-(2-4ft)-SW S3-B1-(2-4ft)-SW S3-B2-(0-2ft)-SW S3-B3-(0-1ft)-SW S4-(0-0.5ft)-LC-SW S5-(0-0.5ft)-LT-SW S6-(0-0.5ft)-LC-SW S15-Canal Side-(0-0.5ft)-LC-SW S15-CanalSide-(0-0.5ft)-HC-SW S15-Levee Crown-(0-0.5ft)-LT-SW S15-Levee Crown-( ft)-LT-SW

94 Overtopping Erosion Levee Overtopping Chart

95 t = 0.80 sec t = 1.60 sec t = 2.39 sec 189 Jean-Louis BRIAUD Texas A&M University SHEAR STRESSES ON LEVEE SURFACE 190 Jean-Louis BRIAUD Texas A&M University 95

96 Fundamentals Bridge Scour Scour depth predictions Observational method Case history Levee Overtopping Hurricanes Floods Case histories Overtopping Erosion Overtopping During Floods Events Midwest Levees Summer

97 Overtopping Erosion 193 Flow Frequency Analysis 7 year flood year flood 13 year flood 6 year flood Overtopping Erosion 194 Winfield Pin Oak

98 Overtopping Erosion 195 Winfield Pin Oak (Failed) 195 Overtopping Erosion 196 Indian Graves (Failed)

99 Overtopping Erosion 197 Norton Woods (Failed) 197 Overtopping Erosion 198 Brevator (Did Not Fail)

100 Overtopping Erosion 199 THE INVESTIGATION Sample Collection In situ testing 199 Overtopping Erosion EFA test results Erosion rate versus water velocity

101 Overtopping Erosion LEVEES Failed and Not Failed Overtopping Erosion Levee Overtopping Chart

102 Overtopping Erosion Vegetative Armor Good grass type and coverage Poor grass type and coverage Levee failure: effect of vegetation 204 Here is an example of what tree damage or other items that have grown too close to the levee can do. (Zina Deretsky, NSF)

103 Overtopping Erosion 205 Recommendations: Vegetative Armor Mat like, sod forming root system Perennial grasses Dense consistent coverage Height ihabove m during flood season Trees limited to 15 m beyond levee toe 205 Overtopping Erosion ELEVATED HOUSES

104 Overtopping Erosion Elevated Houses Jean-Louis Briaud

105 Overtopping Erosion ESCAPE STRUCTURES Fundamentals Bridge Scour Scour depth predictions Observational method Case history Levee Overtopping Hurricanes Floods Case histories

106 tamu edu/briaud/ Briaud s Web Site 6 th International Conference on Scour and Erosion Paris August TH International Conference of Soil Mechanics and Geotechnical Engineering Paris 1 to 5 Sept p// g PANAM Conference Toronto 2 to 6 Oct cgc2011.ca

107 213 If your faucet drips on a pebble for 20 million years, will there be a hole in the pebble?

EROSION FUNCTION APPARATUS

EROSION FUNCTION APPARATUS 51 EROSION FUNCTION APPARATUS Author: Faculty Sponsor: Department: Ryan Larsen Dr. Allen Jones, Dr. Francis Ting Civil and Environmental Engineering ABSTRACT The Erosion Function