hashimoto
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kuliah tamuTRANSCRIPT
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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
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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
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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
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-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
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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
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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%
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“3CaO-Al2O3-3CaSO4-32H2O”
is a hydrogen product called
ettringite.
Effects of different types of binders - Chemical reactions between peat and binder -
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■ SEM(telemicroscope) photo of treated
TESHIO peat using binder at curing of 28days
Mechanism of increase in Strength
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DMM, middle layer mixing method: quf/qul ≒3
Laboratory and field strength
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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
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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
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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
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• 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
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Thank you for your attention