Case History of Cement Stabilization for Peat

Civil Engineering Research Institute for Cold Region, PWRI

Geo-technical Research Team

Research Engineer: HIJIRI HASHIMOTO

IRE-CERI Workshop on Road Construction Technology over Peat 2014

June.5-6, Bandung Indonesia

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• Decision procedure of the ground

improvement method on construction site.

• Construction use and the improved ground

method(Deep mixing method & Middle layer

mixing method) outline.

• Laboratory mixing test and construction

management on improved ground.

• Summary

Content

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Relationship between period and cost

The method to overcome

the trade-off between

PERIOD and COST

Surcharge method

High

Low

Short Long Period

Cost

Deep-mixing method

Lightweight embankment method

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The Division of the cement improvement method of construction

Surface soil

stabilization

Middle layer

Mixing Method

Deep Mixing Method

Deep Mixing Method

The maximum Improved Depth ・・・ 25 m

Deep mixing method

(1)

(2)

(3) (4) (5)

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Trencher type mixing method

A power blender (full view) A trencher mixer

Application of cement-mixing stabilization

Improvement of foundation

ground for retaining walls Prevention of embankment

sliding failure

Embankment

stabilization

Improved soil Improved soil

Bearing layer

soft soil

Bearing layer

-When deep cement mixing is used on peat,

we are often faced with factors that

obstruct solidification due to the organic

matter in peat.

-Even in laboratory tests where uniform

mixing can be performed, peat may not

solidify when using portland or blast

furnace cement.

-It is therefore important to find a way to

choose the most effective binders to use

for peat from the numerous types available.

The problems that cement improves peat

Properties Ebetsu peat Yubarigawa peat Enbetsu peat

Natural water content (%) 380 719 912

Density of soil particles (g/cm3) 1.85 1.60 1.62

Ignition loss (%) 47 70 95

pH 5.1 4.1 5.0

- PEAT： 3 kinds

- CEMENT： 8 kinds

Ordinary Portland cement,

Blast Furnace B-type cement,

Binder

- TEST： Un-confined compression test（JIS A 1216)

Aim： The different of cement and peat effecting

on the improved strength.

Effects of different types of binders - Engineering properties of peat tested -

JGS 0812

BC： The ratio of the cement weight for

the wet weight of the peat

Effects of different types of binders - Results of the unconfined compression test -

EBETSU PEAT YUBARIGAWA PEAT ENBETSU PEAT

Wn=380%

Wn=719%

Wn=912%

“3CaO-Al2O3-3CaSO4-32H2O”

is a hydrogen product called

ettringite.

Effects of different types of binders - Chemical reactions between peat and binder -

■ SEM(telemicroscope) photo of treated

TESHIO peat using binder at curing of 28days

Mechanism of increase in Strength

DMM, middle layer mixing method： quf/qul ≒3

Laboratory and field strength

a

qu

l28=

3・q

uc

k

Quantity of binder （kg/m3）

b c

Blast furnace B-type

cement

Ordinary portland cement

High organic type binder

High organic type

B-type cement

80kg/m3×3000IDR/kg = 240,000IDR/m3

220kg/m3×1000IDR/kg = 220,000IDR/m3

80 150 220

Aim： We decides quantity of kind of economical cement

satisfying design strength (×3 = Lab. strength)

and quantity of binder(cement)

Laboratory mixing test The economic type is adopted from the provides

quantity of binder(cement) and price per 1kg of

each binder(cement)

Portland cement 150kg/m3×1200IDR/kg = 180,000IDR/m3

Construction

Management

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Schedule control

Work progress control

Quality control

Construction management of improved soil

Orderer → Contracter

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①：The strength of specimens to satisfy 85%

of design strength

②：The extreme mean of the test specimen’s

strength to satisfy design strength

Quality control(Standard)

The mean strength greatly exceeds design

strength to satisfy 85% of desigh strength

Un-economical !!

We evaluate the quality of improved

ground in 28 days after construction

Peat： K=0.5

The improved strength were less than

the design strength was 30%.

Work quality strength = quf28_ave – 0.5×σ

desigh

strength

Quality control(CERI)

average

Normal distribution

minimum

quf28

0.5σ σ：standard deviation

Consideration of a defectiveness rate

when we improve peat

• For the peaty ground of Hokkaido, there are

many construction if improved ground.

• When there is much organic content of peat,

even the binder may not solidify.

• It is necessary to choose economical cement

type by the laboratory test.

• The quality control of the improved ground

on peaty ground considers 30% of bad rates.

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Summary

Thank you for your attention