NCHRP Report 516: Pier and Contraction Scour in Cohesive Soils

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Table of Contents
Front Matter R1-R10
Summary 1-7
1.4 Why Was This Problem Addressed? 8-8
1.5 Approach Selected to Solve the Problem 9-9
2.4 Erodibility and Correlation to Soil and Rock Properties 10-13
3.3 EFA Test Data Reduction 14-14
3.4 EFA Precision and Typical Results 15-16
4.2 Small Flood Followed by Big Flood 17-17
4.3 Big Flood Followed by Small Flood and General Case 18-18
4.4 Hard Soil Layer Over Soft Soil Layer 19-20
4.6 Equivalent Time 21-21
4.7 Extended and Simple SRICOS-EFA Method 22-23
4.8 Case Histories 24-25
4.9 Predicted and Measured Local Scour for the Eight Bridges 26-28
4.10 Conclusions 29-29
5.4 Measuring Equipment 30-31
5.5 Soils and Soil Bed Preparation 32-32
5.6 Flume Tests: Procedure and Measurement 33-33
5.8 Shallow Water Effect on Maximum Pier Scour Depth 34-35
5.9 Shallow Water Effect on Initial Shear Stress 36-36
5.11 Pier Spacing Effect on Maximum Scour Depth 37-37
5.12 Pier Spacing Effect on Initial Scour Rate 38-38
5.15 Pier Shape Effect on Initial Scour Rate 39-39
5.18 Attack Angle Effect on Maximum Scour Depth 40-41
5.20 Attack Angle Effect on Scour Hole Shape 42-42
5.21 Maximum Scour Depth Equation for Complex Pier Scour 43-44
6.2 Existing Knowledge on Numerical Simulations for Scour 45-45
6.5 Shallow Water Effect: Numerical Simulation Results 46-46
6.6 Shallow Water Effect on Maximum Shear Stress 47-47
6.7 Pier Spacing Effect: Numerical Simulation Results 48-48
6.9 Pier Shape Effect: Numerical Simulation Results 49-50
6.10 Pier Shape Effect on Maximum Shear Stress 51-51
6.11 Attack Angle Effect: Numerical Simulation Results 52-52
6.12 Attack Angle Effect on Maximum Shear Stress 53-53
6.13 Maximum Shear Stress Equation for Complex Pier Scour 54-55
7.3 Flume Tests and Measurements 56-56
7.4 Flume Tests: Flow Observations and Results 57-58
7.5 Flume Tests: Scour Observations and Results 59-59
7.6 Maximum and Uniform Contraction Depths for the Reference Cases 60-62
7.7 Location of Maximum Contraction Depth for the Reference Cases 63-63
7.8 Correction Factors for Transition Angle and Contraction Length 64-64
7.9 SRICOS-EFA Method Using HEC-RAS Generated Velocity 65-65
7.11 Scour Depth Equations for Contraction Scour 66-67
8.3 Transition Angle Effect: Numerical Simulation Results 68-68
8.4 Contracted Length Effect: Numerical Simulation Results 69-71
8.6 Maximum Shear Stress Equation for Contraction Scour 72-75
9.3 The Integrated SRICOS-EFA Method: Step-by-Step Procedure 76-80
9.5 The SRICOS-EFA Program 81-83
9.6 Output of the SRICOS-EFA Program 84-84
10.4 Gill (1981) Database: Contraction Scour 85-87
10.5 Remarks 88-88
11.2 Preparation of the Future Hydrographs 89-89
11.3 Risk Approach to Scour Predictions 90-90
11.4 Observations on Current Risk Levels 91-92
12.2 Example 2: Single Rectangular Pier with Attack Angle and Approaching Hydrograph 93-94
12.3 Example 3: Group Rectangular Piers with Attack Angle and Approaching Constant Velocity 95-98
12.4 Example 4: Contracted Channel with 90-Degree Transition Angle and Approaching Constant Velocity 99-102
12.5 Example 5: Contracted Channel with 60-Degree Transition Angle and Approaching Hydrograph 103-104
12.6 Example 6: Bridge with Group Piers and Contracted Channel with Hydrograph in Contracted Section 105-110
13.1 Conclusions 111-112
13.2 Recommendations, 113-113
References 114-115
Nomenclature 116-117
Unit Conversions 118-118
Appendix A - Photographs from the Flume Tests 119-125
Abbreviations used without definitions in TRB publications 126-126

Table of Contents

Front Matter R1-R10

Summary 1-7

1.4 Why Was This Problem Addressed? 8-8

1.5 Approach Selected to Solve the Problem 9-9

2.4 Erodibility and Correlation to Soil and Rock Properties 10-13

3.3 EFA Test Data Reduction 14-14

3.4 EFA Precision and Typical Results 15-16

4.2 Small Flood Followed by Big Flood 17-17

4.3 Big Flood Followed by Small Flood and General Case 18-18

4.4 Hard Soil Layer Over Soft Soil Layer 19-20

4.6 Equivalent Time 21-21

4.7 Extended and Simple SRICOS-EFA Method 22-23

4.8 Case Histories 24-25

4.9 Predicted and Measured Local Scour for the Eight Bridges 26-28

4.10 Conclusions 29-29

5.4 Measuring Equipment 30-31

5.5 Soils and Soil Bed Preparation 32-32

5.6 Flume Tests: Procedure and Measurement 33-33

5.8 Shallow Water Effect on Maximum Pier Scour Depth 34-35

5.9 Shallow Water Effect on Initial Shear Stress 36-36

5.11 Pier Spacing Effect on Maximum Scour Depth 37-37

5.12 Pier Spacing Effect on Initial Scour Rate 38-38

5.15 Pier Shape Effect on Initial Scour Rate 39-39

5.18 Attack Angle Effect on Maximum Scour Depth 40-41

5.20 Attack Angle Effect on Scour Hole Shape 42-42

5.21 Maximum Scour Depth Equation for Complex Pier Scour 43-44

6.2 Existing Knowledge on Numerical Simulations for Scour 45-45

6.5 Shallow Water Effect: Numerical Simulation Results 46-46

6.6 Shallow Water Effect on Maximum Shear Stress 47-47

6.7 Pier Spacing Effect: Numerical Simulation Results 48-48

6.9 Pier Shape Effect: Numerical Simulation Results 49-50

6.10 Pier Shape Effect on Maximum Shear Stress 51-51

6.11 Attack Angle Effect: Numerical Simulation Results 52-52

6.12 Attack Angle Effect on Maximum Shear Stress 53-53

6.13 Maximum Shear Stress Equation for Complex Pier Scour 54-55

7.3 Flume Tests and Measurements 56-56

7.4 Flume Tests: Flow Observations and Results 57-58

7.5 Flume Tests: Scour Observations and Results 59-59

7.6 Maximum and Uniform Contraction Depths for the Reference Cases 60-62

7.7 Location of Maximum Contraction Depth for the Reference Cases 63-63

7.8 Correction Factors for Transition Angle and Contraction Length 64-64

7.9 SRICOS-EFA Method Using HEC-RAS Generated Velocity 65-65

7.11 Scour Depth Equations for Contraction Scour 66-67

8.3 Transition Angle Effect: Numerical Simulation Results 68-68

8.4 Contracted Length Effect: Numerical Simulation Results 69-71

8.6 Maximum Shear Stress Equation for Contraction Scour 72-75

9.3 The Integrated SRICOS-EFA Method: Step-by-Step Procedure 76-80

9.5 The SRICOS-EFA Program 81-83

9.6 Output of the SRICOS-EFA Program 84-84

10.4 Gill (1981) Database: Contraction Scour 85-87

10.5 Remarks 88-88

11.2 Preparation of the Future Hydrographs 89-89

11.3 Risk Approach to Scour Predictions 90-90

11.4 Observations on Current Risk Levels 91-92

12.2 Example 2: Single Rectangular Pier with Attack Angle and Approaching Hydrograph 93-94

12.3 Example 3: Group Rectangular Piers with Attack Angle and Approaching Constant Velocity 95-98

12.4 Example 4: Contracted Channel with 90-Degree Transition Angle and Approaching Constant Velocity 99-102

12.5 Example 5: Contracted Channel with 60-Degree Transition Angle and Approaching Hydrograph 103-104

12.6 Example 6: Bridge with Group Piers and Contracted Channel with Hydrograph in Contracted Section 105-110

13.1 Conclusions 111-112

13.2 Recommendations, 113-113

References 114-115

Nomenclature 116-117

Unit Conversions 118-118

Appendix A - Photographs from the Flume Tests 119-125

Abbreviations used without definitions in TRB publications 126-126