Minepastebackfill:theuseof

grou

tsat

massiv

escale

Step

hanJeffe

risEnvironm

entalG

eotechnics

Ltd

Step

henWilson

Hambled

onMiningplc

SYNOPSISOFPA

PER

•Selectionof

cementitious

bind

er•Rh

eology

andpipe

flow

•Co

nsolidation

•Bleeding

•Ch

anne

lledbleed

CONVE

NTIONAL

TAILINGS

MAN

AGEM

ENT

•Tailings

minewaste

afterm

illing

•Fine

tailingstypically80

%passing75

μm•Wet

andeasilyliquefiable

•Po

tentialfor

flowslide

s–occurred

toooften

•Typically

retained

with

intailingsd

amso

rlagoon

s•Largearea

ofland

requ

iredwhich

ultim

ately

mustb

erestored

totheenvironm

ent

Taili

ngs

feed

(slu

rry

pipe

line )

Hyd

rocy

clon

e

Und

erflo

wsa

nd

Ove

rflow

fines

Slim

es

Sup

erim

pose

d po

nd

Cle

an w

ater

Dec

ant r

etur

ned

to p

lant

Dam

Dra

in

Phr

eatic

line

With

gra

tefu

l ack

now

ledg

men

t to

Pro

f Tam

as M

eggy

es, B

AM

Sur

face

pas

te d

ispo

sal

Bul

uyan

hulu

-Ta

nzan

iaW

ith g

rate

ful a

ckno

wle

dgen

t to

Pro

f T. M

eggy

es &

Gol

der A

ssoc

iate

s

Sur

face

pas

te d

ispo

sal

Bul

uyan

hulu

-Ta

nzan

iaW

ith g

rate

ful a

ckno

wle

dgen

t to

Pro

f T. M

eggy

es &

Gol

der A

ssoc

iate

s

AZNALCO

LLAR

,SPA

INFAILED

TAILINGS

DAM

Dam

Breach

INSIDE

THEFAILED

TAILINGS

POND

POTENTIALLY

ACID

GENER

ATINGPYRITE

WAS

TE

CEMEN

TEDPA

STEBA

CKFILL

•Co

nvertin

gaprob

lem

into

asset

•Re

turnsa

prop

ortio

nof

tailingsu

ndergrou

nd(m

axim

um~50

%)

•Ce

mentedmassc

anbe

used

forregionalund

ergrou

ndminesupp

ort

•Pastewillno

tstoproof

cracking

•no

tstiffe

noughbu

twillstop

collapse

•Enablesg

reater

prop

ortio

nof

orebo

dyto

berecovered

•Re

ducesd

ilutio

nof

oredu

ringextractio

n•Re

ducesa

bove

grou

ndstorage

PASTEBA

CKFILL

•Water

may

bescarce

somaxim

umrecovery

ofwater

isde

sirableandachieved

throughthickening

orfiltration

•Und

ergrou

nddisposalredu

ceslandtake

andenvironm

ental

risk

•Acementitious

bind

erisrequ

iredform

aterialplaced

unde

rgroun

das

thematerialretains

water

•Mines

areofteninremotelocatio

ns,how

ever

paste

minim

isesb

inde

rreq

uirementscomparedto

othe

rbackfills

•Ch

emicalandph

ysicalprop

ertie

sofm

inetailingsc

anbe

complex

andvaria

ble

•Re

sidualamou

ntso

fmetalssuchas

copp

er,leadandzin

ccankillor

massiv

elyretard

cementset

WITHGR

OUTS

ONESIZE

DOES

NOT

FITALL

REQUIRED

PROPERT

IES–PA

STEBA

CKFILL

•Econ

omyof

who

leprocess

•Minim

umbind

ercontent

•Exploito

ravoidtailingsc

hemistry

•Minim

umwater

content

•Pu

mpability

•Selflevelling

•Bleed/filtration/consolidationminim

al•Pene

trability

–no

tanissue

ALSO

NEEDTO

SELECT

APPR

OPR

IATE

GROUTBE

HAVIOUR

MODE

LS

Und

ergrou

ndMine

Processin

gPlant

Tailings

Concentrate

Filte

ring

Thickening

Mixing

Bind

er

or

Simplified

PasteBa

ckfill

MaterialFlowDiagram

Backfill

Plant

Water

Recycling

Cob

riza

Min

e, P

eru

Past

e Th

icke

ner

Und

erflo

w

Lish

een

Min

e Pa

ste

Plan

tIre

land

MAS

SIVE

THICKENER

PASTEMIXSTATION

TAILINGS

–BINDE

RMIXER

Typi

cal t

hick

er p

aste

bac

kfill

6-7

inch

slu

mp

Gol

d Ta

iling

s –

Seki

sovs

koye

Min

e, K

azak

hsta

n

Typical

tailings

paste

Testing

Prob

ably

willfin

dabe

tter

one

PIPELINEPR

ESSU

REGR

ADIENT

•Pastemustb

epu

mpableas

itmay

have

tobe

pumpe

dsubstantialhorizo

ntaldistances

but

•Minemay

bede

epso

that

thereisalarge

verticaldrop

•Needto

avoidcavitatio

nandfree

fallof

paste

•Otherwise

severe

damageto

pipe

worketc.

d4

LPw

PIPELINEPR

ESSU

REGR

ADIENT(P/L)

Functio

nof:

shearstressa

twall

w•

pipe

diam

eter

d

BASICRH

EOLO

GY–BINGH

AMMODE

L

bb

Shearstressat

wall

wisafunctio

nof:

•yieldstress

•plastic

viscosity

•shearrate

PRED

ICTIONOFWALLSH

EARSTRE

SS

•Standard

equatio

nexist

forB

ingham

mod

el•bu

tinpracticewalllayer

develops

•Walllayer

ismoreflu

id•Effectismorepron

ounced

insm

allerp

ipes

•Invalidates

simpleBingham

mod

elfora

llgrou

ts!

•andanyothe

rsinglematerialm

odelwhich

considerso

nlybu

lkflu

id•Forp

umping

pressure,needto

consider

onlythewalllayer

ROTATIONAL

VISCOMETRY

•Co

uldtryto

match

shearrates

viscom

eter

pipe

•Co

mplex

andmay

notrep

resent

wallcon

ditio

ns•So

setp

eriphe

ralvelocity

ofshearvane/b

obto

averagelinearv

elocity

inpipe

,Vp

•Use

largediam

eter

cup(in

finite

sea)

pV

dNTestvane

orbo

bin

cupof

grou

t

SHEA

RSTRE

SSONBO

B

Whe

reM

isthetorque

onthebo

b

2DhM2

r

rw

assume

dhDM

8LP

2

Hence

PIPELINEPR

ESSU

REDR

OP

•Shearstresso

nbo

bat

approp

riate

rotatio

nal

speeds

givesa

nindicatio

npu

mping

pressure

•Quick,verysim

ple,no

need

tode

velopfull

rheo

logy

form

aterial

•Provides

aratio

nalbasisforselectio

nof

viscom

eter

rotatio

nalspe

edforo

peratio

nal

QA/QC

•Metho

dology

canbe

refin

edforo

ther

materials/a

pplications