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Estimation of Tailings Dam Break Discharges

Arvind Dalpatram

USSD

Workshop on Dam Break AnalysisApplied to Tailings Dams

August 24-26, 2011

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Overview

Dam break analyses for water storage dams

Relatively simple Lots of guidance available in literature

Often covered by regulatory guidelines

Well established numeric modelling tools/software

available

Dam break analyses for tailings storage dams More complex than water storage dams

Tailings more viscous than water, and not as free flowing

Not all tailings released from impoundment

Numeric modelling tools/software difficult to use or not

reliable

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Overview

Difference between water storage and tailings storage

impoundments

Use of methodology/tools for water storage dams

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Water and Tailings Storage Impoundments

Tailings StorageWater Storage

WaterDam Dam

Free Water

(supernatant pond)Tailings Beach

Tailings

(solids & water)

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After Dam Breach

Tailings StorageWater Storage

DamDam

TailingsWater

BreachBottom

Breach

Bottom

Tailings flow downstream of dam

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Breach to Foundation Level

Tailings StorageWater Storage

DamDam

Tailings

Not all tailings

releasedTailings flow

downstream of dam

All water released

Breach

Bottom

Breach

Bottom

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Volume of Tailings Released

Source

No. of

Dams

Dam

Heights

Tailings Released

Range Average

Lucia (1981) 11 15m to 46m 14% to 100% 40%

USCOLD (1995) 16 20m to 61m 1% to 100% 29%

Garga and Khan (1995) 19 ? 3% to 100% 28%

USCOLD (1995) and

www.tailings.info31 12m to 61m 1% to 100% 26%

M. Rico et al. (2007) 28 5m to 66m 3% to 100% 33%

Azam and Li (2010) 72 ? ? 20%

http://www.tailings.info/http://www.tailings.info/

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Volume of Tailings Released (M. Rico et al.)

Source: M. Rico et al. (2007)

VF = 0.354VT1.01

Where:

VF = Outflow volume

VT = Stored volume

OutflowV

olume(106xm3)

Impoundment Volume (106 x m3)

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Steps for Tailings Dam Break Analyses

Establish dam break scenario

Estimate volume of tailings released

Review flows in downstream river and potential for

transport of tailings Assume released tailings behave like water

Estimate dam breach parameters

Run numeric dam break and inundation model Carryout sensitivity analyses for estimated/assumed

values

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Dam Break Scenarios

Sunny-day Failure

Supernatant pond at max. normal operating level

Normal flows in river(s) downstream of the dam (e.g.,

average annual flow)

Caused by earthquake, seepage, foundation failure, etc.

Rainy-day Failure

Flood-induced failure

Supernatant pond at design flood level, or higher

Flood flows in river(s) downstream of the dam (i.e., flowsmost likely to occur coincident with the breach event)

More water than sunny-day failure; more tailings

mobilized

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Amount of Tailings Mobilized

Impoundment Characteristics

Stage/storage curve

Shape of impoundment

Water in the Impoundment

Free water above the tailings

Water retained within the tailings (i.e., water content)

Flows in the rivers downstream of dam

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Impoundment Characteristics

Dam

Dam

Tailings

Tailings

Free Water

Free Water

Tailings surface after failure

Tailings surface after failure

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Water in the Impoundment and River

Dam

Tailings (solids & water)

Free Water

DamFree Water

Tailings (solids & water)

Sunny-day Failure

Rainy-day FailureWater in river

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Breach Parameters

Breach Geometry

Breach depth

Breach width Breach side slopes

Breach Formation Time

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Dam Break and Inundation Modelling

Conventional dam break and flood routing models

Sensitivity analyses:

Assumed tailings release volume Breach geometry

Breach formation time

etc.

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References

Azam, Sahid and Li, Qiren (2010). Tailings Dam Failures: A Review of the Last One Hundred Years, Geotechnical

News, December.

Garga, V.K. and Khan, M.A. (1995). Review and Comparison of a deterministic Model for estimating Flow Out

Distance of Breached Tailings, report submitted to Resources Canada, Mining Research Laboratory.

Lucia, P.C. (1975). Review of Experiences with Flow Failures of Tailings Dams and Waste Impoundments.

Lucia, P., Duncan, J., and H.B. Seed (1981). Summary of Research on Case Histories of Flow Failures of MineTailings Impoundment, mine Waste Disposal Technology Proceedings Bureau of Mine Technology Transfer

Workshop, Denver, July 16, 2981.

Lucia, P.C. (1981). Review of Experiences with Flow Failures of Tailings Dams and waste Impoundments, PhD

dissertation, University of California, Berkeley.

Rico M., Benito G., and Diez-Herrero A. (2007). Floods from Tailings Dam Failures, Journal of HazardManagement.

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References

USCOLD (1995). Tailings Dam Incidents.

Vick, S. (1992). Inundation Risk from Tailings Dam Flow Failures, Proceedings, IX Pan-American Conference, Van

del mar, Chile, Vol. 1, pp. 1137-1158.

Wahl, T. L. (1998). Predicting Embankment Dam Breach Parameters A Literature Review and Needs Assessment,

Dam Safety Research Report DSO-98-004, US Bureau of Reclamation, Dam Safety Office, July.

www.tailings.info

http://www.tailings.info/http://www.tailings.info/

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Estimation of Tailings Dam Break Discharges

Questions / Comments?