EROSION TECHNOLOGY for SITES EROSION TECHNOLOGY for SITES

Earth Spillway Integrity AnalysisEarth Spillway Integrity Analysis Phase 2: Inputs and Equations Phase 2: Inputs and Equations

EROSION TECHNOLOGY for SITES EROSION TECHNOLOGY for SITES

Earth Spillway Integrity AnalysisEarth Spillway Integrity Analysis Phase 2: Inputs and Equations Phase 2: Inputs and Equations

EROSION MEASUREMENT TRAINING:Maricopa County, AZ October 2011

3 PHASE Spillway Erosion Model

1. SURFACE EROSION (Cover Destruction)

3. HEADCUT ADVANCE

2. CONCENTRATED FLOW EROSION

SPILLWAY EROSION PHASESSPILLWAY EROSION PHASES

1. 1. SURFACE EROSION SURFACE EROSION (Cover Destruction)

2. CONCENTRATED FLOW EROSION 2. CONCENTRATED FLOW EROSION (Headcut Formation)(Headcut Formation)

3. HEADCUT ADVANCE3. HEADCUT ADVANCE

PHASE 2CONCENTRATED FLOW EROSION

PHASE 2PHASE 2Concentrated Flow Surface DetachmentConcentrated Flow Surface Detachment.

rr = k = kdd ( (ee - - cc))

ee = = (d+(d+d)Sd)S

Stress equation applies when eroded depth (d) is less than approach critical flow depth (phase 2).

kkd d = coefficient of detachment (material property)= coefficient of detachment (material property)

cc = critical tractive stress (material property) = critical tractive stress (material property)

SURFACE DETACHMENT

te, (Pa)

0.0 0.2 0.4 0.6 0.8 1.0 1.2

e r, (g

/cm

2 )/s

0

2

4

6

8

10

tc

kd

c e

r

10-1 100 101 102 103 10410-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

10 Clopper and Chen(1988)

9 Chen and Anderson(1987)

8 Shaikh et al.(1987)

7 McWhorter et al.(1968)

6 Hanson(1990)

5 Elliot et al.(1989)

4 Grissinger et al.(1981)

3 Arulanandan et al.(1980)

2 Fuduka & Lick(1980)

1 Partheniades(1965)

e, (N/m2)

r, (g

/cm

2 /s)

1

2

109

8

76

54

3

DETACHMENT RATE COEFFICIENTDETACHMENT RATE COEFFICIENT

The detachment rate coefficient may be externally determined and entered directly in SITES or estimated by SITES from soil properties.

Kd Versus Percent Clayfor Range of dry density values

0.01

0.1

1

10

0 20 40 60 80 100

Percent 2 Microns

Kd

Com

pute

d

d = 120 pcf

d = 100 pcf

d = 110 pcf

d = 90 pcf

d = 130 pcf

Summary of Factors to compute KdSummary of Factors to compute Kd

Dry Density, Dry Density, dd

Percent finer than 2Percent finer than 2 (% clay) (% clay) Practical range is from 0.01 to 10Practical range is from 0.01 to 10 Number is inversely related to resistance to Number is inversely related to resistance to

erosion – low value is high resistance, high erosion – low value is high resistance, high value is low resistancevalue is low resistance

Note units are in ft/hr of downward erosion per Note units are in ft/hr of downward erosion per unit applied stress of lb/ftunit applied stress of lb/ft22

Jet Erosion Test (JET)Jet Erosion Test (JET)

Jet Erosion Test in NY Spillway

CRITICAL STRESS CRITICAL STRESS for for

DetachmentDetachment

Critical stress based on loose particle condition for all materials.

Parameters Impacting Phase 2 ErosionParameters Impacting Phase 2 Erosion

SPILLWAY EROSION PHASESSPILLWAY EROSION PHASES

1. 1. SURFACE EROSION SURFACE EROSION (Cover Destruction)

2. CONCENTRATED FLOW EROSION2. CONCENTRATED FLOW EROSION

3. HEADCUT ADVANCE3. HEADCUT ADVANCE