soft soils preloading & vd (paulus rahardjo - sesi 6)

8/10/2019 SOFT SOILS Preloading & VD (Paulus Rahardjo - Sesi 6)

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Rekayasa Tanah Lunak

PERBAIKAN TANAH LUNAK DENGAN

PRELOADING DAN VERTICAL DRAIN

Prof. PAULUS P. RAHARDJO, Ph.D Parahyangan Catholic University,Bandung – Indonesia



Metode PreloadingTujuan : - Meningkatkan kuat geser tanah dasar

- Mengurangi sifat kemampatan tanah- Mengurangi resiko settlement dikemudian hari



KONSEP

PRELOADING DAN VERTICAL DRAINS



MENINGKATKAN

KUAT GESER TANAH DASAR

hGww nn

1

Gs = berat jenis tanah

= penurunan tanah permukaan

h = tebal lapisan lunak

hS

C

GwS u

c

nu

434.0

.1



Prinsip

Preloading dan Vertical Drain



SAND DRAINS / GRAVEL DRAINS

dan PREFABRICATED VERTICAL DRAINS



Alat Pemancang PVD

Metode Pemasangan Prefebricated Vertical Drain

1. MENGGELAR LAPISAN PASIR SEBAGAISAND BLANKET ALTERNATIF LAIN DENGANPREFABRICATED HORIZONTAL DRAIN

2. MEMASANG VERTICAL DRAINS (PVD)3. MELAKUKAN PENIMBUNAN DAN SURCHARG4. MEMONITOR SETTLEMENT DAN TEKANAN

AIR PORI EKSES5. MEMINDAHKAN SURCHARGE6. MELAKUKAN PERAPIHAN LAHAN SIAP

DIBANGUN



CARA Pemasangan Prefebricated Vertical Drain

Pemasangan Sepatu Pelat

Pemancangan Mandrel

Ke Dalam Tanah




Pencabutan Mandrel

Dari Dalam Tanah

Pemotongan

Ujung Atas PVD




Sambungan Antar Ujung Rol Material PVD



DASAR-2 UNTUK DESAIN

c

o

o

c

o

c

o

s f

p

p p

e

C

p

p

e

hC s log

1log

1

1. PERHITUNGAN SETTLEMENT KONSOLIDASI

2. PERHITUNGAN WAKTU KONSOLIDASI

s = U . Sf

3. PERANCANGAN PRELOAD DAN VERTICAL DRAINS

- tinggi preload ditentukan dari stabilitas dan ketersediaanmaterial timbunan

- kedalaman vertical drain ditentukan dari tebal lapisantanah lunak

- jarak vertical drains ditentukan dari batasan waktu



Perhitungan derajat konsolidasi

vertikal dan radial1 – U = (1 – Uh) (1 – Uv)



Nomogram desain



LOKASI PROYEK DAN KONDISI GEOLOGI

Mahakam river deltaicsoils

Alluvial type withconsiderable thickness,where the soil consist ofmud deposited in afluviatile, deltaic andcoastal environtment



HASIL PENYELIDIKAN TANAH

Void Ratios and Shear Strength

g vs Depth

0

5

10

15

20

25

30

35

40

45

50

1.00 1.50 2.00g (t/m3)

D e p t h

SC 2 SC 1

e initial vs Depth

0

5

10

15

20

25

30

35

40

45

50

0 2 3

e initial

D e p t h

SC 1 SC 2

Su vs Depth

0

5

10

15

20

25

30

35

40

45

50

0 20 40 60 80

Su (kPa)

D e p t h

S C1 S C2

Su / v' vs Depth

0

5

10

15

20

25

30

35

40

45

50

0.0 0.2 0.4 0.6 0.8

Su / v '

D e p t h

SC1 SC2



HASIL PENYELIDIKAN TANAH

Water Content, Plasticity andCompressibility

wn vs Depth

0

5

10

15

20

25

30

35

40

45

50

0 50 100 150

wn (%)

D e p t h

SC1 SC2

Plastic Limit

0

10

20

30

40

50

60

0 25 50 75 100

(%)

D e p t h ( m )

SC1 SC2

Liquid Limit

0

10

20

30

40

50

60

0 50 100 150

(%)

D e p t h ( m )

SC1 SC2

Cc vs Depth

0

5

10

15

20

25

30

35

40

45

50

0.0 0.5 1.0 1.5 2.0

Cc

D e p t h

SC 1 SC 2

E50 vs Depth

0

5

10

15

20

25

30

35

40

45

50

0 20 40 60 80

E50

D e p t h

SC 1 SC 2



Initial Condition of Site

Site Preparation and Reclamation



MENGGELAR GEOTEKSTIL, MENGGELAR PASIR

DAN MEMASANG PVD

Reclamation Program

Soil Improvement by Geotextile,Preloading and the Use of Vertical Drains

INVESTIGASI DAN HASIL REKAMAN



INVESTIGASI DAN HASIL REKAMAN

SP-1 - SP-24 Fill Thickness

0

1

2

3

4

5

6

0 50 100 150 200 250

Time (day)

F i l l T h i c k n e s s ( m )

SP-1 - SP-24 Settlement

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 50 100 150 200 250

Time (day)

S e t t l e m e n t ( m )



Geotechnical Investigation Program

CPTU BEFORE ANDDURINGRECLAMATION WORKS

ill

j

i

i i j

T T 77

< -

D e p t h i n m t o

r e f e r e n c e l e v e l

0123456789

10111213141516171819202122232425

262728293031323334353637383940

0 2 4 6 8 10

SoilBehaviour Type

after Robertson,1986S l eeveresi stance, fs(M Pa) P orepressure, u2(MPa) Pore pressure ratio,Bq

0123456789

10111213141516171819202122232425

262728293031323334353637383940

0 0.05 0.1

0123456789

10111213141516171819202122232425

262728293031323334353637383940

0 0 .2 0 .4 0 .6 0 .8 1

0123456789

10111213141516171819202122232425

262728293031323334353637383940

0 1 2 3 4 5 6 7 8 9 10

0123456789

10111213141516171819202122232425

262728293031323334353637383940

0 0.2 0.4 0 .6 0.8 1 -----------

Cone resistance,qc(MPa) Friction r atio,FR(%)

0123456789

10111213141516171819202122232425

262728293031323334353637383940

(8) Sand to siltysand

(9) Sand

(3) Clays

(3) Clays

(1) Sensitive, finegrained

(1) Sensitive, finegrained

(5) Clayeysilt to siltyclay

(6) Sandysilt to clayeysilt

(6) Sandysilt to clayeysilt

(6) Sandysilt to clayeysilt(6) Sandysilt to clayeysilt



UJI CPT-U SEBELUM DIMULAI PENIMBUNAN

fs (kg/cm2)

0

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0 0.5 1

SC 2 SC 1

qc (kg/cm2)

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0 10 20 30 40

SC 2 SC 1

u (kg/cm2)

0

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51

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53

54

-2 0 2 4 6 8 10

SC 2 SC 1

OCR

Lunne et all, 1997

0

1

2

3

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0 1 2

SC 2 SC 1

K0

Kulhawy and

Mayne, 1990

0

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0 1 2

SC 2 SC 1

Su (kg/cm2)

Campanella et all,

1980

0

1

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0 0 .1 0 .2 0 .3 0 .4 0 .5

SC 2 SC 1



PTu were conducted during the period of waiting time before fill removal

Typical CPTu test result during reclamation

< - D e p t h i n m t o

r e f e r e n c e l e v e l

0

123456789

1011121314151617181920212223242526272829

3031323334353637383940

0 2 4 6 8 10

Soil Behaviour Type

after Robertson,1986Sleeve resistance,fs(MPa) Pore pressure,u2(MPa) Pore pressure ratio,Bq

0

123456789

1011121314151617181920212223242526272829

3031323334353637383940

0 0.05 0.1

0

123456789

1011121314151617181920212223242526272829

3031323334353637383940

0 0.2 0 .4 0 .6 0 .8 1

0

123456789

1011121314151617181920212223242526272829

3031323334353637383940

0 1 2 3 4 5 6 7 8 9 10

0

123456789

1011121314151617181920212223242526272829

3031323334353637383940

0 0.2 0 .4 0 .6 0 .8 1

Cone resistance,qc(MPa) Friction ratio,FR(%)

0123456789

1011121314

151617181920212223242526272829

3031323334353637383940

(8) Sand to silty sand

(9) Sand

(3) Clays

(3) Clays

(1) Sensitive, fine grained

(1) Sensitive, fine grained

(5) Clayey silt to silty clay

(6) Sandy silt to clayey silt

(6) Sandy silt to clayey silt

(6) Sandy silt to clayey silt(6) Sandy silt to clayey silt



PTu were conducted during the period of waiting time before removal

Comparison of Old and New CPTu test results

The Comparison of qc Value of Soft Soil

Before and After Preload

0

10

20

30

40

50

60

0 0.5 1 1.5 2

qc (MPa)

D e p t h ( m )

CPTU SC-1 PCPT-01

The Comparison of fs Value of Soft Soil


0

10

20

30

40

50

60

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04

fs (MPa)

D e p t h ( m )

CPTU SC-1 PCPT-01

The Comparison of u2 Value o f Soft Soil


0

10

20

30

40

50

60

0 0.2 0.4 0.6 0.8 1

u2 (MPa)

D e p t h ( m )

CPTU SC-1 PCPT-01



Determination of the degree of consolidation of Reclaimed

Site on deep soft Mahakam deltaic soils using CPTu

Higher qc and fs may be due to increased shear strength

UNDERSTANDING THE MEASUREMENT OF CPTu ON RECLAIMED SITE

Response from CPTU

qc =‘higher’ tip resistance

f s = ‘higher’ friction

u2 = ‘higher’ pore pressure

u1

u2

u3

u2

up = excess pore pressure due

to cone penetration

u = residual excess pore pressure

u0 = hydrostatic pore water pressure






u1

u2

u3

u2

up = excess pore pressure due

to cone penetration

u = residual excess pore pressure

u0 = hydrostatic pore water pressure

ui

Log time

uf = u0

ui

Log time

u0

uf

ReclaimedSite

UnreclaimedSite






Dissipation Curve At 9.825 m

140

160

180

200

220

240

0.01 0.1 1 10 100 1000

Time (Min.)

P o r e p r e s s u r e ( K P a )

Log time

u due to cone

penetration

u50

t50

ui

u100

uf

u50

u0

u residual excess pore

pressure

u50 = (ui-uf )/2



Degree of Consolidation interpreted by Method ofextrapolation of dissipation test

Dissipation Curve at 8.38 m t50 = 59.95 Minute

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

1 10 100 1000 10000

Log Time (Min.)

E x c e s s P o r e W a t e r P

r e s s u r e ( M P a )

Measured Extrapolated t50 u0

Excess Pore Pressure Due

To Insertion Of CPTu Cone

Excess Pore Pressure

Due To Fill Material

Hydrostatic Pore Water Pressure

U [%] = 1-(ut/ui)

U [%] = 1-(ut/p)

p = pressures dueto fill placement



ASAOKA 9.825 m, PIK

100

125

150

175

200

225

250

100110120130140150160170180190200210220230240250

ut[KPa]

u t +

t [ K P a ]

Depth = 9.82 m

u0 = 68 kPa

uf = 117 kPa

ut = 117-68 = 49 kPa

= 64.6 kPa

U = 24.54 %

Dissipation Curve At 9.825 m

140

160

180

200

220

240

0.01 0.1 1 10 100 1000

Time (Min.)

P o r e p r e s s u r e ( K

P a )

uf = 117 Kpa

EXAMPLE OFCALCULATION



PTu were conducted during the period of waiting time before removal

Degree of Consolidation interpreted empiricalcorrelations

OCR vs Depth

0

10

20

30

40

50

60

0.00 1.00 2.00 3.00 4.00 5.00

OCR

D e p t h ( m )

SC-1

SC-2CPTu k=0.413

best fit the value of k=0.413

'.

0

0

v

vt qk OCR

Powell, 1988

k = 0.2-0.5



CONCLUSIONSSite Characterization of the deltaic soils using CPTu is best

It is concluded that the site is homogeneous deep soft clayswith increasing strength vs depth

The CPTu conducted before and after fill placement givevery clear understanding of the soft ground response. Thechanges in strength and pore pressure are identified.

A simple technique is developed and can be used to predictthe degree of consolidation by extrapolation of thedissipation test results. In general the degree ofconsolidation of the reclaimed site achieved before removalwas 85%

Next Challenge : CAN CPTU PREDICTS



Next Challenge : CAN CPTU PREDICTSWHEN THE MUD ERUPTIONS IN EASTJAVA WILL STOP?

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soft soils preloading & vd (paulus rahardjo - sesi 6)

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