DESIGNANDEXECUTIONOFGROUNDINVESTIGATIONFOREARTHWORKS
ABSTRACTThedesig
a
dexecutio
ofgrou
di
vestigatio
worksforearthworkprojectshasbecomei
creasi
glyimporta
tastheavailabilityofsuitabledisposalareasbecomeslimiteda
dcostsofimporti
ge
gi
eeri
gfilli
creaseA
outli
eofgrou
di
vestigatio
methodswhichca
augme
t‘traditio
ali
vestigatio
methods’particularlyforglacialtillboulderclaysoilsisprese
tedTheissueof‘geotech
icalcertificatio
’israiseda
d
recomme
datio
soutli
edo
itsmeritsfori
corporatio
withgrou
di
vestigatio
sa
dearthworks1INTRODUCTIONThei
vestigatio
a
dreuseevaluatio
ofma
yIrishboulderclaysoilsprese
tsdifficultiesforboththegeotech
icale
gi
eera
dtheroaddesig
e
gi
eerTheseglacialtillorboulderclaysoilsaremai
lyoflowplasticitya
dhaveparticlesizesra
gi
gfromclaytobouldersMostofourboulderclaysoilsco
tai
varyi
gproportio
sofsa
dgravelcobblesa
dbouldersi
aclayorsiltmatrixTheamou
toffi
esgover
stheirbehavioura
dthesiltco
te
tmakesitveryweathersusceptibleMoistureco
te
tsca
behighlyvariablera
gi
gfromaslowas7forthehardgreyblackDubli
boulderclayupto2025forMidla
dSouthWesta
dNorthWestlightgreyboulderclaydepositsTheabilityofboulderclaysoilstotakei
freewateriswellestablisheda
dpoorpla
i
gofearthworksofte
amplifiesthisThefi
esoilco
stitue
tsarege
erallyse
sitivetosmalli
creasesi
moistureco
te
twhichofte
leadtolossi
stre
gtha
dre
derthesoilsu
suitableforreusease
gi
eeri
gfillMa
yofourboulderclaysoilsespeciallythosewithi
termediatetypesiltsa
dfi
esa
dmatrixhavebee
rejectedattheselectio
stagebutgoodpla
i
gshowsthattheyca
i
factfulfilspecificatio
requireme
tsi
termsofcompactio
a
dstre
gthTheselectio
processshouldaimtomaximisetheuseoflocallyavailablesoilsa
dwithcarefulevaluatio
itispossibletouseori
corporate‘pooror
fmargi
alsoils’withi
fillareasa
demba
kme
tsFillmaterial
eedstobeplacedatamoistureco
te
tsuchthatitis
eithertoowettobestablea
dtrafficableortoodrytobeproperlycompactedHighmoistureco
te
tlowstre
gthboulderclaysoilsca
besuitableforuseasfilli
lowheightemba
kme
tsie2to25mbut
otsuitablefortrafficki
gbyearthworkpla
twithoutusi
gageotextileseparatora
dgra
ularfillcappi
glayerHe
ceitisvitalthattheearthworksco
tractorfullyu
dersta
dstheha
dli
gpropertiesofthesoilsasforma
yprojectsthisiseffectivelygover
edbythetrafficabilityofearthmovi
gequipme
t2TRADITIONALGROUNDINVESTIGATIONMETHODSApri
cipalaimofthegrou
di
vestigatio
istoclassifythesuitabilityofthesoilsi
accorda
cewithTable61fromSeries600oftheNRASpecificatio
forWorksSRWMarch2000Themajorityofcurre
tgr