TURNERFAIRBANK HIGHWAY RESEARCH CENTER Interaction between Riprap Layout

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Interaction between Riprap Layout and Contraction Scour from Vertical-Wall Bridge Abutments Supported by Shallow Foundations presented by Huang, C. , Xie, Z. , Suaznabar, O. Shen, J. and Kerenyi, K. at the NHEC Friday, August 12 th, 2016 Portland, OR

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Outline • Needed additional guidance—HEC-23 Riprap Countermeasure – Better address the common stream bank conditions – Single-span bridges built close to the main channel • Development of proper Layout for Riprap Countermeasure – Experimental study – CFD study • Preliminary Conclusions 2

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER HEC-23 Riprap Installation Top of Shallow Foundation at the same Elevation as Contraction Scour + Long Term Degradation Topic 1 3

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER HEC-23 Riprap Installation HEC-23 D. G. 14 for Bridge Abutments Topic 1 4

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER HEC-23 Riprap Installation HEC-23 D. G. 18 for Bottomless Culverts Topic 1 5

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Experiment Results Clear-Water Scour – Edge Failure HEC-23 D. G. 14 HEC-23 D. G. 18 Edge Failure: Due to narrower erodible width and change of bed roughness: Increased Contraction Scour Side Slope Installation Edge and Slide Failure: combined effect of Local and Contraction Scour: Riprap Stability – Edge Failure 6

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Edge Failure of Riprap • Why riprap edge fails? Two side effects of riprap installed on the surface: – Narrower erodible width (volumetric effect) – Change the bed roughness (roughness effect) Model Without riprap Model With riprap 7

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Edge Failure of Riprap Cont’d • Why riprap edge fails? Two side effects of riprap installed on the surface: – Narrower erodible width (volumetric effect) – Change the bed roughness (roughness effect) Model Without riprap Model With riprap 8

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Edge Failure of Riprap Cont’d • Less edge failures risk for wider openings High Shear Lead to Edge Failure Model without riprap Model with riprap 9

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER CFD Modeling – Compound channels Field Installations y 1 CFD Modeling Channel Geometry 10

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER CFD Modeling – Compound channels No riprap - compound Riprap - compound CFD Models – compound channel 11

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Bed shear stress (Riprap size =1’ 9’’) Case 26 (W 2/y 0 = 6. 2) No riprap Riprap CFD Results - Bed Shear Stress 12

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Case 30 (W 2/y 0 = 16. 0) No riprap Riprap CFD Results - Bed Shear Stress 13

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Results for Full Scale Modeling CFD (V 2=5. 1 ft/s) 2, 40 CFD results 2, 20 CFD (V 2=5. 7 ft/s) 2, 00 Theoretical derivation 1, 80 1, 60 CFD (V 2=6. 6 ft/s) Curve-fitting (V 2=5. 1 ft/s) 1, 40 Curve-fitting (V 2=5. 7 ft/s) 1, 20 1, 00 4, 0 6, 0 8, 0 10, 0 12, 0 14, 0 16, 0 Curve-fitting (V 2=6. 6 ft/s) Theoretical Derivation – CFD and Curve-fitting 14

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Field Cases Towlston, VA VA (W 2=34', (W 2 =34’, y 1=7. 5') y 0 =7. 5’) Towlston, 11 STH 40, WI (W 2 =34', y 0 =4. 23') STH 40, WI (W 2=34', y 1=4. 23') Guthrie Run, DE (W 2 =27', y 0 =1. 5') Guthrie Run, DE (W 2=27', y 1=1. 5') Forestry Service Rd, PA (W 2 =33', y 0 =4') Forestry Road, Service. NV Road, PA y =11. 7') Nordyke (W 2 =57', 0 (W 2=33', y 1=4') 9 7 5 3 1 0 4 8 12 16 20 Theoretical Derivation – Definition of Narrow Opening 15

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Importance of Riprap • When the bridge abutments are built in the main channel and NOT buried below total scour – Riprap becomes part of bridge structure (riprap failure = bridge failure) – No riprap failure => No surface installation – New layout is needed 16

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Proposed Layout for Riprap Countermeasure for Shallow Foundations • Free Surface Flow – – Riprap Layouts based on Scour for Scour Check Flood Option 1: No riprap for abutments, foundation buried below total scour Option 2: Riprap buried below long term degradation (LTD) + check flood contraction scour Option 3: Riprap buried below long term degradation (LTD) + check flood contraction scour , full width protection across the stream bed • Pressure Flow – – Riprap Layout based on Contraction Scour for Scour Design Flood Riprap buried below vertical contraction scour, full width protection across the stream bed 17

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Free Surface Flow: Option 1 Cross Section View 18

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Free Surface Flow: Option 2 For W 2 / y 0 (CF) > 6. 2 Cross Section View 19

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Free Surface Flow: Option 3 Cross Section View 20

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Pressure Flow Cross Section View 21

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Free Surface Flow: Option 1 Plan View 22

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Free Surface Flow: Option 2 Plan View 23

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Free Surface Flow: Option 3 Plan View 24

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Pressure Flow Plan View 25

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Buried Full Width Protection W 2/y 0 = 6. 2 Apron extent = 2 y upstream and downstream Narrow Bridge Openings – Buried Full Width Protection 26

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Buried Full Width Protection Cont’d W 2/y 0 = 6. 2 No Shear, No Edge failure observed Narrow Bridge Openings – Buried Full Width Protection 27

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Bed Shear Stress For Model Without/With Buried Riprap Case 31 (W 2/y 0 = 6. 2) No riprap Buried Riprap CFD Results - Bed Shear Stress 28

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Bed Shear Stress For Model Without/With Buried Riprap Case 32 (W 2/y 0 = 8) No riprap Buried Riprap CFD Results - Bed Shear Stress 29

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Bed Shear Stress For Model Without/With Buried Riprap Case 35 (W 2/y 0 = 16) No riprap Buried Riprap CFD Results - Bed Shear Stress 30

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Preliminary Conclusions • For new bridges with shallow foundations built in the main channel, implement proposed layout for riprap countermeasure. No riprap edge failure is allowed when abutments are not buried below the total scour depth of check flood. Preliminary Conclusions 31

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER Thank you! 32