Culvert Risk Assessment Guideline Training Notes€¦ · the Risk Assessment Application (RAA)...

CULVERT RISK ASSESSMENT TRAINING WORKSHOP

Prepared 05/04/11

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WHAT RISK ??

Apr 2011

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Apr 2011

Are we at risk?

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Apr 2011

LEARNING OUTCOMES

1. Understand the current RTA culvert management process

2. Learn how to analyse inventory data and identify asset defects

3. Learn how to undertake risk assessments of culverts using the Risk Assessment Application (RAA) software to derive ASSESSED RISK LEVEL (ARL)

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Prepared DD/MM/YYYY




Apr 2011

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DAY 18:30 - 8:45 am Introduction (AC)8:45 - 9:00 am Culvert Management Framework (AC)9:00 - 9:30 am Inventory Collection Process (SJ)9:30 - 10:00 am Risk Assessment Process (Part 1) (GW)10:00 - 10:15 am Video on Culvert Failure Mechanisms (AD)10:15 - 10:30 am Morning Tea10:30 - 11:30 am Risk Assessment Process (Part 2) (GW)11:30 - 12:30 pm Worked Examples (AD)12:30 – 1:15 pm Lunch1:15 - 2:30 pm Remedial /Monitoring Actions (AD) 2:30 - 5:30 pm Field Inspection (AD)

TRAINING COURSE PROGRAM

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DAY 28:30 - 8:45 am Day 1 Review and Form Completion (AD)8:45 - 10:15 am Risk Assessment Application (RAA) (MM)10:15 - 10:45 am Morning Tea10:45 - 11:00 am Next Steps (SJ)11:00 - 12:15 am Worked examples (AD/MM)12:15 - 1:00 pm Lunch1:00 - 4:00 pm Group Activities (using field data to derive ARL)

(AD/MM)4.00 – 4.30 pm Questions (All)

TRAINING COURSE PROGRAM

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COURSE OUTLINE

• Culvert Management Framework

• Culvert Inventory Collection

• Risk Assessment Identify Hazards Estimate likelihood of failure Estimate consequence of failure Derive Assessed Risk Level (ARL)

• Risk Assessment Application

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•Policy PN 211 was approved in Sept 2009•Management of Culverts include:

– Culvert inventory and condition– Assessment (risk based approach)– Allocation of funds

• Intended outcomes:– Culvert risks systematically identified & assessed– Long term maintenance & funding needs assessed– Maintenance programs appropriately prioritised– Whole of life cost of maintaining culverts is reduced

Culvert Management Framework POLICY OVERVIEW

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•Culvert Inventory Collection Guideline– Available on RTA internet site

•Culvert Risk Assessment Guideline•Rehabilitation Guideline

Culvert inventory and risk assessment to be managed in central RTA database within RAMS

Culvert Management Framework ASSOCIATED DOCUMENTS

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COURSE OUTLINE

• Culvert Management Framework

• Culvert Inventory Collection



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CULVERT INVENTORY COLLECTION

Discovering the number and condition of culverts

Culvert Inventory Collection Guideline

Culvert Inventory Collection

Culvert Data Collection Form

•Identification•Culvert Location•Design Data•Culvert Details

Summary of Requirements•Identification•Culvert Location•Design Data•Culvert Details•Culvert Condition•Drainage Pits•Photo and Image files



Summary of Requirements•Identification•Culvert Location•Design Data•Culvert Details•Culvert Condition•Drainage Pits•Photo and Image files•Risk Assessment check list



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Risk Assessment Checklist

CHECKLIST ITEM EXAMPLE PHOTO

SUBSIDENCE

IN THE ROAD


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EXTENSIVE PATCHING OF THE ROAD ABOVE THE CULVERT

Presence of multiple patches in roadway above the culvert;

Patching to repair shape of roadway – i.e - sub-pavement distress;

If patching repaired roadway - guardrail may be sagged.


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SIGNIFICANT CRACKING OR DEFORMATION OF THE ROAD ABOVE THE CULVERT

Longitudinal or transverse cracking above the culvert, greater than 5mm wide;


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HOLES OR CAVITIES IN THE ROAD FILL AROUND THE INLET OR OUTLET OR ABOVE THE CULVERT

Localised depressions in the the roadway above the culvert;

Holes already established in the embankment.


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EMBANKMENT FAILURE AT THE CULVERT OUTLET

(SLUMPING, CRACKING)

Detached/ missing end structures (Headwalls, wing walls) at culvert outlet;

Significant batter slump;

Debris at inlet / outlet;

Cracking in pavement Headwall / wingwall detached.

Voids or scour holes behind the headwall

SEEPAGE EMERGING AROUND THE OUTSIDE OF THE PIPE

Water visually exiting out from under and around the culvert barrel.

Evidence of backfill entering into the barrel.


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SEVERE SCOUR EROSION OF THE ROAD FILL BATTERS

Voids directly above culvert greater than 150 mm deep

Overtopping of the roadway – some debris remaining under guardrail;

Batter slump / significant scouring.

SEVERE SCOUR EROSION BELOW THE OUTLET OR AT THE INLET

Overtopping of the roadway – some debris remaining under guardrail;

Slumping on inlet higher up embankment;

Scour on outlet side of embankment.


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HEADWALLS MISSING OR DISPLACED

Missing headwall / wing wall.

Headwall / wingwall separation that allows embankment material to erode between the culvert and headwall.

INCONSISTENT FLOW OF WATER BETWEEN INLET AND OUTLET

Visual flow or water flowing into pipe but not out.

Visual flow or water flowing out of the pipe but not in.


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SQUEEZE POINT AND/OR LOCALLY STEEP BATTER

Noticeable hinge points in embankment due to road widening but not culvert lengthening;

Batter slope steeper than 1:1.


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EXTENSIVE CRACKING AND DEFORMATION OF THE INTERNAL WALLS

Cracks in concrete barrel units that run for the length of the unit – hairline cracks included;

Cracking in headwall may indicate further cracking inside pipe;

Any water or fill ingress into the culvert.


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EVIDENCE OF CORROSION OF STEEL REINFORCEMENT

Rust and pitting marks on the exposed steel reinforcement at any location on the concrete barrel.

SPALLING OR DELAMINATION OF CONCRETE

Slices of concrete have fallen away from the main culvert.

Exposure of steel re-inforcement.


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NOTICEABLE DISPLACEMENT OR SEPARATION ACROSS JOINTS

Evidence of water or embankment entering the pipe through cracks or through joints.

Visible vertical displacement in butt joints.

EVIDENCE OF GROUNDWATER ENTERING INTO THE PIPE

Deposits of soil backfill in the culvert invert that has entered through cracks (i.e. not debris that has flowed through the pipe).

Water flowing out of pipe not flowing into inlet.

Water coming through the culvert joints.


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EVIDENCE OF EROSION THROUGH JOINTS

Deposits of soil in the culvert invert.

Scour holes and voids around the culvert barrel.

Depressions and sags on the roadway above the culvert.

Seepage inflows carrying fines, soil accumulation at joints).

BOWING OF CULVERT Ponding of water in the centre of the culvert.

Visually the centre of the culvert appears lower than the outlet.

NOTE here the sideways diversion of the waterflow indicating a bending of the culvert base


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BUSINESS RULES

RULE 1 (Culvert Performance)ROAD

• Subsidence• Patching• Cracking • Holes/cavities • History of water over road

CULVERT• Seepage around the outside• Inconsistent flow of water between inlet and outlet• Metal, plastic, terracotta, masonry, timber, composite, • Significant cracking and deformation of the internal walls• Displacement or separation joints (butt ≥ 20mm, spigot and socket ≥ 50mm)• Erosion through joints • Water being lost out of joints

ENVIRONMENT• Occupied at risk buildings downstream (within 100m)

RULES 2/3 (Squeeze point/ High Embankment)• Embankment failure at the culvert outlet eg slumping, cracking• Significant scour erosion of the road fill batters• Significant scour erosion below the outlet or at the inlet• Headwalls missing or displaced• Squeeze point and/ or locally steep batter

• Culvert conveys tidal flows or has floodgates present

RULE 4 (Culvert Structure)• Corrosion of steel reinforcement • Spalling of concrete• Displacement or separation across joints (butt ≥ 20mm, spigot and socket ≥ 50mm)• Groundwater entering pipe• Bowing of culvert• Geometry change• Debris or vegetation inside culvert• Acid sulphate soils and/or acid bearing rock

RULE 5 (Large Culvert)•Larger Dia ≥ 900mm or equivalent waterway area

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Risk Assessment Checklist The Comment Box

If inspector believed that immediate danger to the public, the word “URGENT” entered into the comment box.

The following cases indicated the requirement to use the word “Urgent”:

• 50% or greater blockage of the inlet, outlet or culvert barrel;• Cracking extending past the travelled lane;• Guardrail hanging;• Props in culvert• Unplanned utilities in culvert• Significant dip in the pavement; and• Anything posing a danger to vehicles / public.

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CULVERT RISK ASSESSMENT COURSE OUTLINE

•Culvert Management Framework•Culvert Inventory Collection



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OVERVIEW OF CULVERT RISK ASSESSMENT GUIDELINE

• Introduction (pages1-3)• Risk assessment Methodology (pages 5-10)• Risk Assessment Planning (pages11-13)• Risk Assessment Procedure (page14)• Culvert Risk Assessment Record (pages15-34)• Failure Modes (pages 35-65)• Likelihood Rating (pages 35-66)• Consequence Rating (pages 67-73)• Assessed Risk Level (page 74)• Assessment Completion (page 75)

•This training course is based on this guideline

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RISK ASSESSMENT INTRODUCTION

1. Culvert Management Framework2. Risk Assessment Roles3. Risk Assessor needs to be aware of:

i. Confined space requirementsii. Traffic control at worksitesiii. Industrial rope useiv. GPS unit use limitationsv. Environmental requirementsvi. Heritage requirements

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RISK ASSESSMENT - PART 1

RISK ASSESSMENT METHODOLOGY

Establish Context

Identify Hazards

Analyse Risks

Evaluate Risks

Treat Risks

Likelihood

Consequences

Estimate level

Communicateand consult

Monitorand Review

Establish Context

Identify Hazards

Analyse Risks

Evaluate Risks

Treat Risks

Likelihood

Consequences

Estimate level


Monitorand Review

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• Risk Management Process 1. Hazard Identification2. Likelihood Analysis3. Consequence Analysis4. Assessed Risk Level

Establish Context

Identify Hazards

Analyse Risks

Evaluate Risks

Treat Risks

Likelihood

Consequences

Estimate level


Monitorand Review

Establish Context

Identify Hazards

Analyse Risks

Evaluate Risks

Treat Risks

Likelihood

Consequences

Estimate level


Monitorand Review

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HAZARD IDENTIFICATION (pp35-65)

Kinds of Hazards – Ten possible kinds of culvert failure mechanisms have been defined under four broad modes

SC Structural Collapse SC-1 Structural collapse of the barrel

SI Slope InstabilitySI-1 Slope Instability Caused by AffluxSI-2 Slope Instability Caused by Leakage out of the BarrelSI-3 Slope Instability Caused by Headwall CollapseSI-4 Slope Instability Caused by Undermining at the Inlet or Outlet

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HAZARD IDENTIFICATION (pp35-65)

PI Piping PI-1 Piping into the CulvertPI-2 Piping on the Outside of Culvert due to AffluxPI-3 Piping on the Outside of Culvert due to Leakage out of the

HF Hydraulic FlowHF-1 Erosion by Overtopping FlowsHF-2 Cross-Catchment Flooding

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Establish Context

Identify Hazards

Analyse Risks

Evaluate Risks

Treat Risks

Likelihood

Consequences

Estimate level


Monitorand Review

Establish Context

Identify Hazards

Analyse Risks

Evaluate Risks

Treat Risks

Likelihood

Consequences

Estimate level


Monitorand Review

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LIKELIHOOD ANALYSIS (P 35-66)

The likelihood of failure refers to the possibility of the hazard occurring and extending over a given zone of influence.

EACH MODE OF FAILURE HAS ITS OWN LIKELIHOOD ESTIMATION Eg: For Structural Collapse:

Likelihood of failure SC-1

= Likelihood of collapse of culvert barrel (table SC-1.1)

x Likelihood of void or settlement at road surface

(table SC-1.2)

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LIKELIHOOD RATING (L) (P 66)

Likelihood to L Rating Conversion

Likelihood L Rating

Description

Above 0.5 L1 The event may, or is expected to, occur within a short period under average circumstances, or the mechanism is active at present

0.05 to < 0.5 L2 The event may, or is expected to, occur within a moderate period

0.005 to < 0.05 L3 The event could be expected to occur at some time over about a 100 year period

0.0005 to < 0.005 L4 The event would not be expected to occur within about a 100 year period

0.00005 to < 0.0005

L5 The event would not be expected to occur within about a 100 year period

< 0.00005 L6 The event is unlikely to occur even under extreme circumstances.

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Establish Context

Identify Hazards

Analyse Risks

Evaluate Risks

Treat Risks

Likelihood

Consequences

Estimate level


Monitorand Review

Establish Context

Identify Hazards

Analyse Risks

Evaluate Risks

Treat Risks

Likelihood

Consequences

Estimate level


Monitorand Review

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CONSEQUENCE ANALYSIS (P 67-73)

Purpose is to identify the effects of the hazards on the elements at risk

Elements at risk include:• Road users • Infrastructure (eg. railways);• Buildings (occupied and unoccupied) • Structures• Pedestrians • Services (eg. water supply, power poles); • Road and furnishings • Other property.• Vehicles

Potential consequences (effects):• Loss of life (C to be derived from temporal/vulnerability)• Damage to property and consequential effects (refer example)

• Road closure • Infrastructure or property damage and consequential costs • Repair costs

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CONSEQUENCE FOR RISK TO LIFE (pp67-72)

The consequence of a hazard resulting in loss of life must be estimated using the following rating scales.

• Temporal probability (T) of a person being present within the zone of influence of the failure,

• Vulnerability (V) of such a person.

These scales are combined through a matrix to derive a consequence rating.

The consequence rating derived relates to the indicative probability of death of an individual,

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METHODOLOGY Illustrated Example

InletOutlet

Potential slip circle

Culvert

Direction of slip

water

CL

Parameters determining ARL:

L – probability that failure mechanism occursT – probability a car is on the road and drives into voidV – expresses probability that death or damage occurs as result of the failureC is derived from T and VARL is derived from L and C

T

LInlet

Outlet


Culvert

Direction of slip

water

CLCL


L – probability that failure mechanism occursT – probability a car is on the road and drives into voidV – expresses probability that death or damage occurs as result of the failureC is derived from T and VARL is derived from L and C

T

L

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METHODOLOGY Illustrated Example

Inlet

Outlet


Culvert

Direction of slip


L – probability that failure mechanism occursT – probability a person is in building at time of impactV – expresses probability that death or damage occurs as result of the failureC is derived from T and VARL is derived from L and C

LTInlet

Outlet


Culvert

Direction of slip


L – probability that failure mechanism occursT – probability a person is in building at time of impactV – expresses probability that death or damage occurs as result of the failureC is derived from T and VARL is derived from L and C

LT

CONSEQUENCE MATRIX Risk to life (p71)

Consequence Matrix for Risk to Life

Temporal Probability of an Individual Being Present at the Time of Failure

Vulnerability T1 T2 T3 T4 T5

V1 C1 C1 C2 C3 C4

V2 C1 C1 C2 C3 C4

V3 C2 C2 C3 C4 C5

V4 C3 C3 C4 C5 C5

V5 C4 C4 C5 C5 C5

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CONSEQUENCE RATING (C) Risk to property (pp71-72)

Consequence Risk for Property

Rating Description Example

C1 Total closure of a Sub-Network Rank 5 or 6 (SN5-6) road for an extended period

Major infrastructure or property damage (other than road)Very high disruption cost (other than road users)Very high repair cost(Total direct and indirect costs > $10M)

C2 Total closure of one carriageway of an (SN5–6) road or total closure of an (SN3-4) road for an extended period

Substantial infrastructure or property damageLarge disruption costsHigh repair cost(Total direct and indirect costs > $2M < $10M)

C3 Partial or total closure of an (SN3-4) road for a short period, longer period if reasonable alternatives are available

Moderate infrastructure or property damageModerate disruption costsModerate repair cost(Total direct and indirect costs : $0.5M < $2M)

C4 Partial or total closure of an (SN2) road for a short period

Minor infrastructure or property damageMinor disruption costsLow repair cost(Total direct and indirect costs > $0.1M < $0.5M)


Negligible infrastructure or property damageLittle or no disruption costsVery low – no repair cost(Total direct and indirect costs < $0.1M)

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Establish Context

Identify Hazards

Analyse Risks

Evaluate Risks

Treat Risks

Likelihood

Consequences

Estimate level


Monitorand Review

Establish Context

Identify Hazards

Analyse Risks

Evaluate Risks

Treat Risks

Likelihood

Consequences

Estimate level


Monitorand Review

AD

Assessed Risk Level Matrix

Consequence Class

Likelihood C1 C2 C3 C4 C5

L1 ARL1 ARL1 ARL1 ARL2 ARL3






ASSESSED RISK LEVEL (ARL) (p74)

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RISK ASSESSMENT - PART 2 (Risk Analysis)

• Assessment of each hazards and estimating likelihood• Vulnerability and temporal probability estimates• Consequence Ratings• Deriving Assessed Risk Level• Next steps in risk management

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RISK ANALYSIS – FORM (p95)

M . R is k A n a l y s is H a z a r d /F a i lu r e M e c h a n is m

S C - 1 S I - 1 S I - 2 S I - 3 S I - 4 P I - 1 P I - 2 P I - 3 H F - 1 H F - 2

H a z a r d T y p e

S t r u c tu r a l C o l la p s e

S lo p e I n s ta b i l i t y A f f lu x

S lo p e I n s ta b i l i t y L e a k a g e O u t o f B a r r e l

S lo p e I n s ta b i l i t y H e a d w a l l C o l la p s e

S lo p e I n s t a b i l i t y U n d e r -m in in g

P ip in g I n t o C u lv e r t

P ip in g O u ts id e o f C u lv e r t d u e t o A f f lu x

P ip in g O u ts id e o f C u lv e r t d u e t o L e a k s o u t o f C u lv e r t

H y d r a u l ic F lo w E r o s io n b y O v e r -t o p p in g F lo w s

H y d r a u l ic F lo w C r o s s C a tc h -m e n t F lo o d in g

L ik e l ih o o d R a t in g s

L ik e l ih o o d F a c to r 1



F in a l L ik e l ih o o d

L ik e l ih o o d R a t in g ( L 1 - L 6 )

C o n s e q u e n c e C la s s R a t in g s *

T e m p o r a l P r o b a b i l i t y ( T 1 - T 5 )

V u ln e r a b i l i t y ( V 1 - V 5 )

C o n s e q u e n c e C la s s fo r L o s s o f L i fe ( C 1 - C 5 )

C o n s e q u e n c e C la s s fo r p r o p e r t y d a m a g e ( C 1 - C 5 )

R is k A n a l y s i s R a t in g s

A s s e s s e d R is k L e v e l ( A R L 1 - A R L 5 )

N e e d fo r fu r t h e r in v e s t ig a t io n ? ( Y /N ) Y e s N o C o m m e n t s :

* I n g e n e r a l t h e T , V a n d C r a t in g s w i l l b e t h e s a m e fo r e a c h k in d o f h a z a r d , e x c e p t f o r H F - 2 w h ic h w i l l h a v e a la r g e r z o n e o f in f lu e n c e ( ie a c r o s s o th e r c a tc h m e n ts ) .

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STRUCTURAL COLLAPSE SC – 1 (p35)

GW

STRUCTURAL COLLAPSE Likelihood (Pages 35-38)

Factors• Culvert type • Depth of cover.• Culvert condition • Loss of supporting material.

Likelihood of failure SC-1

= Likelihood of collapse of culvert barrel (table SC-1.1)

x Likelihood of void or settlement at road surface

(table SC-1.2)

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SLOPE INSTABILITY SI – 1 (caused by afflux) (p39)

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SLOPE INSTABILITY SI-1 Likelihood (Pages 39-41)

Factors• Hydraulic capacity • Potential for flooding• Location• Material• Foundation• Embankment

Likelihood of failure SI-1

= Likelihood of storm event exceeding

capacity(table S1-1.1 )

or Likelihood of culvert blockage or

insufficient hydraulic capacity

(table SI-1.2)

x Likelihood of instability of road

embankment (table SI-1.3)

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SLOPE INSTABILITY SI – 2 (caused by leakage) (p42)

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SLOPE INSTABILITY SI -2 (Caused by leakage SI -2) Likelihood (Pages 42-44)

Factors• Conditions • Scour undermining the toe• Observed condition of embankment• Embankment material and compaction• Foundation Material•Downstream slope


= Likelihood of leakage out of culvert (table SI-2.1)

x Likelihood of embankment slope instability (table SI-2.2)

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SLOPE INSTABILITY (Caused by head wall collapse SI -3)

Likelihood (Pages 45-46)

Factors• Depth of soil at road embankment• The distance from the headwall to the edge line (EL)• The amount of erosion• A squeeze-point at this location• Guard rail is bolted to the headwall


= Likelihood of headwall collapse

(table SI-3.1)

x Likelihood of pavement collapse given headwall

collapse(SI-3.2)

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SLOPE INSTABILITY (Undermining at inlet/outlet SI – 4)

Likelihood (Pages 46-49)

Factors• Energy dissipation measures at the inlet or outlet• Erosion protection measures at the inlet or outlet• Evidence of scour at the inlet or outlet• Water energy – grade and roughness.


= Likelihood of excessive erosion at the outlet or

inlet(table SI-4.1a and table SI-

4.1b)

x Likelihood of road/culvert collapse

(table SI-4.2)

HB

PIPING PI-1 (Piping into culvert) (p50)

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PIPING PI- 1 (Piping into culvert PI -1) Likelihood (Pages 50-52)

Factors• Culvert type.• Condition of joints, evidence of cracks/corrosion • Surrounding soil conditions • A source of seepage into the culvert

Likelihood of failure PI-1

= Likelihood of erosion into culvert

(table PI-1.1)

x Likelihood of void or settlement at road

surface(table PI-1.2)

PIPING PI-2 (Piping on outside of culvert due to afflux PI -2)

Likelihood (Pages 53- 55)

Factors• Hydraulic capacity of the culvert• Potential for blockage at the inlet.• Embankment material and compaction • Hydraulic gradient for seepage through the embankment• Duration of ponding of water

Likelihood of failure PI-2

= Likelihood of storm event

exceeding capacity(table P1-2.1)

or Likelihood of culvert blockage or

insufficient hydraulic capacity

(table PI-2.2)

x Likelihood of piping failure of road embankment(table PI-2.3)

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PIPING PI-3 (Piping on outside of culvert due to leakage PI -3)

Likelihood (Pages 55- 58)

Factors• Embankment material and compaction • Culvert type• Velocity of flow within the culvert• Condition of joints, evidence of cracks/corrosion

Likelihood of failure PI-

3

= blank Likelihood of internal scour causing piping(table PI-3.2)

x Likelihood of road/void collapse

(table PI-3.3)

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HYDRAULIC FLOW HF-1 (Erosion by overtopping flows HF -1) (p59)

HB

HYDRAULIC FLOW HF-1 (Erosion by overtopping HF -1)

(Likelihood Pages 59-62)

Factors• Hydraulic capacity of culvert; and• Potential for blockage at inlet.• Embankment geometry • Surface cover on slope (vegetation);• Slope of embankment; and• Amount of water and its velocity.

Likelihood of failure

HF-1

= Likelihood of storm event

exceeding capacity(table HF-1.1)

or Likelihood of overtopping of road

embankment(table HF-1.2)

x Likelihood of overtopping causing excessive erosion

(table HF-1.3)

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HYDRAULIC FLOW HF-2 (Cross catchment flooding) (p62)

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HYDRAULIC FLOW HF-2 (Cross catchment Flooding) (Likelihood Pages 62 - 65)

Factors• Hydraulic capacity of the culvert• Potential for blockage• Geometry of road embankment

Likelihood of failure

HF-2

= Likelihood of storm event exceeding capacity

(table HF-2.1)

or Likelihood of culvert blockage

or insufficient hydraulic capacity

(table HF-2.2)

x Likelihood of cross catchment

flooding(table HF-2.3)

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CONSEQUENCE RATING (C) (pp67-73)

The consequence of a hazard resulting in loss of life must be estimated using

1. Temporal probability (T) of a person being present within the zone of influence of the failure, at the time of failure,

2. Vulnerability (V) of such a person.

Vulnerability (V) rating, Temporal probability (T) rating, and thus Consequences (C) ratings are same at one culvert for any hazard (except HF-2)

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CONSEQUENCE RATING

The consequence of a hazard must be considered for two cases:•Loss of Life•Property

Each is dealt with separately in the Guidelines

The higher consequence class will determine risk level

CONSEQUENCE RATING (C) Vulnerability V (Pages 67-68)

Extended Vulnerability Table

Vulnerability Rating

Vulnerability Element Probability

People in the Open People in Buildings Vehicle Crossing Embankment Failure Area

V1 Unable to evade debris (movement very/extremely rapid), or buried

Engulfed in building collapse

Lost into a deep, narrow void. p > 0.5

V2 May be able to evade debris

Partial building collapse Lost into a shallow void p 0.1 – 0.5

V3 Most people able to evade debris

Building penetrated, no collapse

Stepped surface with 0.1 – 0.2 m steps at highway speeds.Aquaplaning as a result of travelling at highway speeds.

p 0.01 – 0.1

V4 Building struck, damaged but not penetrated

Stepped surface with 0.1 – 0.2 m steps at urban speeds.Shallow void/depression where guardfence may prevent a vehicle from leaving the road.Aquaplaning as a result of travelling at urban speed.

p 0.001 – 0.01

V5 Building struck, only minor damage etc

Stepped surface with 0.1 – 0.2 m steps at low speeds.Irregular surface formed by a developing embankment failure at highway speeds.Water on the road causing some loss of control of the vehicle.

p < 0.001

CONSEQUENCE RATING (C) Vehicle impacting voids/stepped surface (P 68)

Vehicle Impacting Voids or Stepped Surfaces

Void Type Posted Speed LimitHighway Speeds(100 – 110 km/hr)

Urban Speeds(60 – 80 km/hr)

Low Speeds(<= 50 km/hr)

Deep, narrow void V1 V2 V3

Shallow void (0.2 – 0.5 m step) V2 V3 V4

Stepped surface (0.1 – 0.2 m steps) V3 V4 V5

Shallow void with guard fence V4 V4 V4

Irregular surface (steps < 0.1 m) V5

CONSEQUENCE RATING (C) Temporal probability estimation (T) (P 69)

Temporal Probability table

Rating Description ProbabilityT1 Person usually expected to be present as part of the normal pattern of

usage (eg residential buildings, some commercial buildings). Road users in the heaviest of urban traffic conditions.

(p > 0.5)

T2 Person often expected to be present as part of the normal pattern of usage (eg many commercial buildings). Road users on major urban arterial roads and the most heavily trafficked rural roads.

(p 0.1 – 0.5)

T3 Person may sometimes be present as part of the normal pattern of usage. Road users on many urban arterial roads and most major rural arterial roads.

(p 0.01 – 0.1)


(p 0.001 – 0.01)


(p < 0.001)

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CONSEQUENCE RATING (C) Temporal probability rating for road users (P 70)

Allocation of Temporal Probability Rating by Traffic Volume

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

Traffic Volume (Vehicles/Lane/Day)

Tem

pora

l Pro

babi

lity

T5

T4

T3

T2

T1

Cla

ss

270

2,650

17,500

GW

Consequence Matrix for Risk to Life

Temporal Probability of an Individual Being

Present at the Time of Failure

Vulnerability T1 T2 T3 T4 T5

V1 C1 C1 C2 C3 C4

V2 C1 C1 C2 C3 C4

V3 C2 C2 C3 C4 C5

V4 C3 C3 C4 C5 C5

V5 C4 C4 C5 C5 C5

CONSEQUENCE RATING (C) Matrix for Risk to Life (P 71)

GW

CONSEQUENCE RATING (C) Consequence for risk to property (P 72-73)

Consequence Risk for Property

Rating Description Example

C1 Total closure of a Sub-Network Rank 5 or 6 (SN5-6) road for an extended period

Major infrastructure or property damage (other than road)Very high disruption cost (other than road users)Very high repair cost(Total direct and indirect costs > $10M)

C2 Total closure of one carriageway of an (SN5–6) road or total closure of an (SN3-4) road for an extended period

Substantial infrastructure or property damageLarge disruption costsHigh repair cost(Total direct and indirect costs > $2M < $10M)

C3 Partial or total closure of an (SN3-4) road for a short period, longer period if reasonable alternatives are available

Moderate infrastructure or property damageModerate disruption costsModerate repair cost(Total direct and indirect costs : $0.5M < $2M)


Minor infrastructure or property damageMinor disruption costsLow repair cost(Total direct and indirect costs > $0.1M < $0.5M)


Negligible infrastructure or property damageLittle or no disruption costsVery low – no repair cost(Total direct and indirect costs < $0.1M)

HB


Consequence Class








ASSESSED RISK LEVEL (ARL) (P 74)

HB


Consequence Class








ASSESSED RISK LEVEL (ARL)

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