chapter 1 exploration
TRANSCRIPT
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05/11/16 Planning 1
Site Exploration Purpose: Identifcation o stratifcation
and important engineering properties Strength, deormation and hdraulic
Inormation needed: or decision on
oundation tpe, !earing capacit,
settlement estimation, identifcation oen"ironmental pro!lem and pertinentsolution#
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%ote Allowance must be given for possible
design changes as excavation for
construction could reveal newconditions that were not evident duringexploration phase.
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Planning an Exploration
Program Planning: 'aximi(e inormation and minimi(e
cost) International practice sho*s soil exploration can cost
0#5 to 1+ o total proect cost# - conser"ati"e design tending to sa"e on exploration
cost does not guarantee saet and e"en econom#
Erratic soil does not necessaril impl need or
extensi"e !oring# .he aim in this case should !eesta!lishment o general picture o stratifcation*ith conser"ati"e design ultimatel#
'aximi(e se o -"aila!le inormation
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Steps in a Soil Exploration
Program -ssem!l o inormation: on tentati"e laout,
unction, special eatures, etc# .his ma in"ol"econsulting dierent maps and preliminardra*ings
2econnaissance/-ppraisal: *al3 o"er site tore"eal crac3s, sags, stic3ing doors 4 *indo*s,etc# tpe o existing structures gull trenchesroc3 outcrops an other rele"ant ino#
Preliminar In"estigation: e* !orings toesta!lish general ormation one or a e* deep!oreholes to competent strata i upper soil isloose
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Steps in data should su7ce or preliminar design 4
identifcation o construction method 8sheeting,diaphragm *all, pile *all, tie!ac3s, etc#9 suita!ilit
o site 4 econom esta!lished# etailed In"estigation: Purpose is to refne
design and decide on an special constructionmethod in"estigation extent depends on
preliminar data generall, it in"ol"es morein"estigation *ith one or more !oreholes tocompetent roc3#
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Exploration 'ethods epending on the unction, si(e, and
importance o the structure, one or
more o the ollo*ing explorationmethods can !e emploed ;pening test pits and/or trenches
Sin3ing !oreholes <eophsical in"estigation <eological in"estigation
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.est Pit and .renches -d"antages
=heap,
ast,
ena!le direct "isual inspection
<ood samples can !e extracted
isad"antages Shallo* in"estigation
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@oring 'ethods @oring has t*o phases: -d"ancing hole
4 sampling#
'an techniAues a"aila!le: ependanton material encountered and purpose# -d"ancing techniAues: -ugering, *ash !oring
, percussion drilling, rotar drilling, continuoussampling, displacement method, etc#
Sampling techniAues: Spiral, !uc3et, hollo*Bstem augers, solidB and splitBspoon samplers, Shel!Btu!e 8thin *all9, stationar piston, singleB and dou!letu!e roc3 core !arrels#
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@oring 'ethods .*o 'aor Pro!lems: =a"ing o *all 4
hea"ing o !ottom#
Dea"ing: occurs in all holes due to stressrelease serious !elo* <. due to seepage useo drilling Fuid maintained a!o"e <. helps#
=a"ing: serious in cohesionless deposits and
!elo* <. also in ointed roc3 !elo* <.depending on degree o *eathering at the ointsthus, use o casings or dri"e pipes !elo* <. iscommon#
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-ugering Dand -ugers: 8a9 Ship or helical 8!9 closed spiral
8c9 open spiral 8d9 I*an or postBhole auger#
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-ugering Po*er -ugers %eed po*er or rotation 4 pressure
Garing si(e and capacit in t*o maor
categories: Fight augers 85 to 1$0cm Φ9 4!uc3etBtpe augers 8&0 to $0cm Φ9#
@uc3etBtpe augers: ;pen top slotted 4 teethed!ottom the !ig si(es can accommodate an inspector#
Hlight augers: SingleBFight, dou!leBFight, high spiral,
con"eorB or continuousBFight, and hollo*Bstemaugers attaching additional height o spiral in thesingleB and dou!leBFight augers is common to sa"e
time
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-ugering =on"eorBFight auger: eep penetration can !e
attained up to &0m 'ixing up o material is adisad"antage#
Dollo*Bstem augers: Internal diameter ranges!et*een >cm and 16 cm consists o a steel tu!e*ith spiral !lades also suita!le or loose deposits!elo* <. center stem and plug replaced !sampler during sampling tu!e ser"es as casing
high Aualit samples can !e retrie"ed SP. can !econducted#
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-ugering Po*er -ugers:
Penetration & to >m
a9 singleBFight earthauger
!9 dou!le Fight earthBroc3auger
c9 dou!leBFight roc3
augerd9 high spiral auger
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-ugering Po*er -ugers
Penetration at
least &0m 8up to100m9
a9 =on"eor Fight auger
!9 @uc3et auger
c9 Dollo*Bstem auger
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-ugering .pical truc3Bmountedauger rig
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ash @oring Starts ! dri"ing a casing o $ to m length#
=asing is cleaned ! chopping !it and
pressuri(ed *ater# 2aising, rotating 4 dropping o !it is necessar#
Is *idel emploed in S# -merica, -rica 4-sia#
@it is replaced ! sampler during sampling#
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ash @oring 8schematic9 Schematic representation
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Percussion rilling =ommon in drilling *ater *ells#
In"ol"es alternate raising 4 dropping o hea"
drilling tools, pouring o *ater and periodical!ailing or pumping o slurr tpe o !itdepends on material encountered#
-d"antageous in coarse granular deposits *ith!oulders and in ca"ernous limestone#
- maor disad"antage: the hea" !lo*s candistur! soil to a signifcant depth di7cult todetect thin laers#
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Percussion .ruc3B
mountedPercussion
drilling rig
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2otar rilling ses rotation 4 pressure or ad"ancement#
'ost rapid in less fssured roc3s#
@entonite mud/slurr or casing necessar ica"ing is a pro!lem#
Garious drill heads ma !e emploed: augerheads grinding heads coring !its etc
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2otar rilling
- hdraulicBeed rotar drilling rig
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2otar rilling
2otardrilling
!its
a9 Hishtail
!9 Da*thorn
c9 =ar!ide
d9 .ricone
e9 iamond
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Samples 4 Sampling .*o tpes o samples
istur!ed !ut representati"e:
Structure could !e lost !ut should contain allconstituents in proper proportion Emploed or identifcation, *ater content,
compaction tests and locating !orro* materials#
Jndistur!edK Digh care exercised to preser"e structure -rea ratio ma not exceed 1&+
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Samples -rea ratio, -r:
%1002
22
×−=i
ior A
φ φ φ
φo is outerdiameter
φi is inner diameter
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Samplers Split-barrel (split-spoon) sampler 'ost commonl emploed or distur!ed/
representati"e samples
φiL &? to 115mm in 1$#5mm incrementsML5 and 60cm tL6#mm#
.he φiL &?mm !arrel is popular !ecause o
existing correlations !et*een % and soil
properties) Hor minor structures, design is commonl
made on the !asis o data rom such samples
- num!er o inserts or soil retention are u
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Samplers .pical splitB!arrel
sampler andsample retainers
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Thin-wall (Shelby)tube sampler 'ost commonl used
tL1#5 to &#$mm φ L 50and >5mm M L 60 and>6cm
se o φ L 100 and150mm is no*adasspecifed ! someauthorities# -d"#: Itena!les to cut out oursamples or triaxial test)
Samplers 8undistur!ed9
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Samplers### Thin-wall (Shelby)…
φi o cutter: 0#5 to 1#5+ o φi o tu!e#
rust protection on the internal *all isnecessar i tu!e is steel# sed in sot to sti cohesi"e soils#
ri"ing emploed in hard cohesi"esoil#
pon retrie"al, a!out $#5cm o thesoil on !oth ends is remo"ed andplaced in a tight ar or moisturecontent and other tests#
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Samplers### Piston Samplers
Thin-wall stationaryPiston Sampler 2etention is ! creating "acuum =onsists o a thinB*all tu!e
sampler, a piston, a 1$#5mm
piston rod and a modifedsampler head#
φi L &5 to 1$5mm M L &5 to
>5cm most common: φi L
>&mm *ith M L >5 cm thatretrie"es a sample 60cm long#
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Samplers### Thin-wall stationary piston…
sed in sot to sti cohesi"e soil
Procedure: Sampler *ith piston lo*ered Piston rod is fxed and tu!e pushed 8ne"er
dri"en9 at >#5 to 15 cm/s#
Excellent Aualit o sample can !eo!tained
- *ide "ariet o this is a"aila!le
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Samplers### Osterberg (double) piston samplers
'odifcation o Shel! *ith additional
actuating piston and a pressure clinder Sampling done ! pressuri(ed *ater on top
o the actuating piston orcing this and thesampler past the stationar piston
Sampler assem!l is pulled out *hen thet*o pistons come in contact
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Samplers### Osterberg (double) piston … Schematic
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Samplers### Swedish Foil samplers
;!ecti"e: to increase sample length per operation# Sample length up to $5m in one go is possi!le))
ltimate goal: to sample o"er!urden to frm laer in one go# Principle: entire elimination o sliding resistance# Equipment consists o sampler head, series o
!arrels and a loosel ftting Foating piston attachedto a rod or chain extending to surace# Sampler head: has tapered !ottom *ith sharp cutting
edge and a dou!leB*all upper section housing !" rolls ometal oils o t # $%$& or $%!&mm attached to the piston#
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Samplers### Swedish Foil%%%
EAuipment
'arrels: ML$#5m and φi L 6? interconnected !special longitudinall split coupling that reducedistur!ance during its remo"al
Procedure: Sampler *ith piston loc3ed to !arrel !ottom is
lo*ered# Piston is reed rom !arrel, !ut the rod to *hich it
is attached is loc3ed to drilling rig to 3eep pistonat one le"el throughout operation#
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Samplers### Swedish Foil%%%
Procedure .he strips o oils un*ind en"eloping the entering
sample as the remainder o the sampler is pushed# -dditional !arrels are added as needed# pon completion, sampler is pulled out# -s a !arrel
emerges it is uncoupled rom the lo*er one exposing asmall section o oil co"ered sample# Hoils are cut,
!arrel capped and the exposed part retrie"ed in a ar# sed primaril in sot cohesi"e soils and uniAuel
adapted or thinl stratifed and "er sot soils#
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Samplers### Swedish Foil…
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Sounding .ests B
Standard Penetration .est <eneral
e"eloped around 1C$>
Standardi(ed in -S.' since 1C5? 8as -S.'15?69
;riginall de"eloped or sand !ut used or allsoils presentl
Principle: resistance is proportional to soundness
=on"ention: SP. e"er 1 to $m starting roma!out 1#5m !elo* ground surace
Ena!les a!out 50+ sample reco"er#
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SP.### Schematic
representatio
n o threecommonlused SP.hammers
Asrat:
Asrat:
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SP.### Procedure
Standard split !arrel 85cm long9 dri"en !
hammer: mL65g and ree allL>6cm @lo*s needed or e"er 15cm penetration
recorded
.otal !lo* count or the last $x15cm is %B"alue
.est is stopped i 50 !lo*s could not sin3 an 15cm increment 100 !lo*s could not sin3 last &0cm increment 10 !lo*s produce no ad"ance at all
Asrat:
Note that earlier to about 1967, N-value was the count
for the 1st 30cm-penetration, which could nearly mean a
50 reduction from the present standard! "nfortunately,
many #$% correlations in current use are based on this
earlier procedure!
Note that earlier to about 1967, N-value was the count
for the 1st 30cm-penetration, which could nearly mean a
50 reduction from the present standard! "nfortunately,
many #$% correlations in current use are based on this
earlier procedure!
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SP.### Inherent pro!lems
'isleading !lo* count can arise rom *arped sampler encountering !oulders Auic3 condition !elo* <.
ith proper attention paid, ho*e"er,these pro!lems can !e o"ercome#
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SP.### -dustments
%B"alues are not reproduci!le in
adacent !oreholes and ! dierenteAuipment mainl due to energ loss Input energ is constant:
E Whkg m s m J
in == × × =63 5 9 81 0 76 475
2. . .
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SP.### Eecti"e energ "aries !et*een &0 to
100+ o Ein
Possi!le sources or the energ loss: ierence in manuacturer
Dammer confguration
se o liner
;"er!urden eect
@orehole si(e
2od length
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SP.### efning energ ratio ound thus
important:
@lo* counts rom an eAuipment can
no* !e standardi(ed to a selected Er ,sa Erb so that a soil is characteri(ed
! a uniAue %B"alue#
E E E r a in= × 100%
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SP.### Galues o Er! suggested in the past:
50 to 55+ ! Schmertmann 81C>C9
60+ ! Seed et al 81C?59 S3empton 81C?69 >0 to ?0 + ! 2iggs 81C?69
>0+ ! @o*les 81CC69
@ased on @o*les suggestion, thestandardi(ed %B"alue !ecomesthen ′ = × × × × × N C N N 70 1 2 3 4η η η η
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SP.### .he correction actors η1, η$, η&, η, are
or energ, rod length, liner, and
!orehole si(e, respecti"el 8a"aila!le in@o*les 81CC69#
.he adustment or eecti"eo"er!urden is
%ote that
C p kPa N = ′9576 0. ( )
E E r r 1 2=
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SP.### ηi L1 or ErL>0+, lrN 10m, no liner and
φ!h ≤1$0mm
esign -*alues: Earl Practice: .he smallest or the a"erage
in a stratum
=urrent Practice: *eighted a"erage
N N Z Z av i i i= ∑ ∑
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SP.### Oi is depth o increment
Hor ooting, a"eraging is done o"er the
inFuence (one 8 I#e#, rom @/$ to $@ !elo*ooting !ase9
+orrelations: %B"alues ha"e !een correlated *ith γ ,r,
φ, Au, Ault and Es# se o correlations on recent adusted %B
"alues is recommended 8see @o*les 81CC699#
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=one Penetration .est
8=P.9 <eneral
e"eloped in Dolland
Standardi(ed in -S.' 8as -S.' &19 @ecoming amous or sot clas, sot silts and
fne to medium sand deposits 8common in deepdeposits o Food plains, ri"er deltas 4 coastlines9
EAuipment consists o 60 cone *ith -!L10cm$ 8or Ac9
.apered slee"e 8to separate s3in riction9
Qac3et 8or As9
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=P.### .pes
,echanical or utch +one Electric Friction 81st modifcation9: emplos
strain gauges or simultaneous measurement oAc and As#
Electric Pieo./riction: measures Ac, As, and u#
Seismic cone: ses "i!ration sensor to recordsismic *a"es rom generated rom hammerimpact at the surace# It ena!les to compute <s
and Gs#
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=P.### .pical
mechanical andelectric
conepenetrometers
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=P.### Procedure: utch =one
=one alone is pushed at 10 to $0mm/s and
Ac measured .hen ac3et alone is pushed and As
measured
Hinall, !oth cone and ac3et are pushed
and Atot measured:( )
q q q
f q q
tot c s
r s a
= +
= × 100%
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=P.
.pical output
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=P.###
Procedure: Electric Hriction in"ol"es continuous push 8no startBstop9
Ac and As recorded electronicall through nonnections
to strain gauges and plotted
-d"antages: Hast, especiall *ith E- sstem
-llo* continuous recording
seul in "#sot soils
allo*s correlations as is the case *ith SP.
Shortcomings Inapplica!le in dense and sti soils
Interpretation demands good experience
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=P.### =lassifcation
chart !ased
on =P. results