Construction Materials - Siva 09 FBook
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Transcript of Construction Materials - Siva 09 FBook
Use of Problematic Soils as Engineered Fill for
Embankments
BySiva Theivendrampillai
SivakumarPrincipal Engineer (Geotechnical)
Geotechnical Branch
The problematic soils considered are:
• Expansive Soils
• Dispersive Soils
• Erodible Soils
• Problematic Soils - Normally “unsuitable materials”.
• Significant quantities of excavated materials are problematic soils. eg. High Plastic Clays
• It is very difficult to source good quality materials locally for some projects
• Cost-effective to use some or all excavated materials with constraints
WHY
Expansive ClayHigh Plasticity Clays - Potential to change in volume with a change in moisture.– Swelling upon wetting
– Shrinkage upon drying
Some indicative values for highly reactive/expansive soils:• Shrink-Swell Index > 3%• CBR Swell > 4-5% (Standard compaction, 4 days soaked)
• WPI > 3200 • LS > 12%
• Potential (eg. CH clay)• Placement (eg. Compaction Condition)• Environment (eg. Arid/Wet) - Atmospheric
Edge Effects
ShoulderSealed Surface
SeasonalVariations
for UncoverdArea
Stable Long TermConditions BeneathCentre of Pavement
DynamicMoistureBalance
Edge Effects on Pavement due to Moisture Balance
0
1
2
3
4
5
6
7
8
0 1000 2000 3000 4000 5000 6000 7000Weighted Plasticity Index (WPI)
Shrin
k-Sw
ell I
ndex
WPI Vs Shrink-Swell IndexData from:Dalby-Miles (Yarralla Dev)Dalby-Miles (Macalister)Mt Isa-Camooweal (Barkly Hwy)Cramsie-Muttaburra (Longreach)Toowoomba-Dalby (Lagoon Creek)Toowoomba-Dalby (Doctor’s Creek)
Gregory Hwy (Emerald)Goomeri-Gayndah (Burnett Hwy)Mackay-BucasiaCunningham Hwy (FG5417)Yandina-Cooroy (Bruce Hwy)Linkfield (Brisbane - R3380)
r2=0.57
Expansive Embankment Materials
LongitudinalCracks
CunninghamHighway
Average Properties:PI = 41%LS = 17%WPI = 3660Iss = 3.3
Effect of Embankment Batter Slope on Pavement Cracking
3m
3m
AssumedActive Zone3m Horizontal
Batter Slope1V:1.5H
Batter Slope1V:4H
Expansive Soil
Expansive Soil
Expansive ClaysIn Queensland
Keith Wallace (1988)
Moisture Rich >500mm/yrMoisture Hungry <500mm/yr
Dispersive SoilsClay content has a high percentage of sodium. Therefore the clay fraction readily breaks down to form a suspension in water.Indicative value for dispersive soils:
Emerson Class Number ≤ 3
Exchangeable Sodium Percentage (ESP) > 2%
A Test for Dispersive Soils
Dispersive Embankment
Materials
Warrego Highway Marburg
Cunningham Hwy Aratula
Piping or Tunnelling
DispersiveSoil
Augustine HeightsNear Springfield
Erodible SoilsLack of cohesion to resist flow of water.
Silty/Sandy soilsPI < 7 and/or
fines < 15 % (that is, % passing 0.075mm)
Rate of erosion depends on several factors such as:– Soil Properties (eg. Porosity and permeability)– Rainfall intensity– Batter slope– Vegetation
* Material that is inferior to Class D is unsuitable material
-≤ 503200 < 4000Class D*
--2200 < 3200Class C
--1200 < 2200Class B
15 – 30≥ 7< 1200Class A
% passing 0.075 mm AS Sieve
PI (%)WPIMaterial Description
Embankment Material PropertiesAs per MRTS04 (MRS11.04)
WPI = PI x % passing 0.425 mm sieve
Embankment Zones
1 to 2 m
PavementSubgrade
Upper ZoneOuter Zone
CORE ZONE
2.5m
In generalCore Zone: Expansive Clays (Class C/D), Dispersive/Erodible SoilsUpper and Outer Zones: Better Materials (Class A/B)For details: Refer MRTS04 (MRS 11.04)
Embankment Height >10m should be geotechnically designed.
Min
1.0 m when Class C and 1.5 m when Class D in
core
High
0.6 m when Class C and 1.0 m when Class D in
core
Low toMedium
Between 1V:2H and
1V:2.5H
A, B
0.6 m when Class C and 1.0 m when Class D in
core
High
A, BA, B
A, B, C
A, B, C, D
1.0Low toMedium
1V:2.5H(or
shallow)Greater
than1.5 m and less
than or equal to
6m
Outer Upper Core
General Fill ClassUpper Zone Thickness
(m)
Homogeneous
Cross-Section
Zoned Cross-SectionRainfall
Zone Batter Slope H (m)
Embankment Height between 1.5m and 6m (from MRTS 04)
Y
PavementSubgrade
Min 2.5m
5 m
Class A/B Class A/B
Class A/B
Class A, B, C, D
To be geotechnically designed>10
ROCK FILLLow to High
1V:1.5H(or
shallow)≤ 10
AAA, BHigh
A, BA, BA, B
A, B, C, D
1.5 m when Class C
and 2.0 m when
Class D in core
Low toMedium
1V:2H(or
shallow)
Greater than6 mAnd≤10 m
Outer Upper Core
General Fill Class Upper Zone Thickness
(m)
Homogeneous
Cross-Section
Zoned Cross-Section
Rainfall Zone
Batter SlopeH (m)
Embankment Height greater than 6m(from MRTS 04)
* These limits apply to material without added water. Where water is added to achieve compaction, the limits shall be 85 – 110.
60 – 8060 – 8060 – 8050 – 80< 500Low
80 – 10080 – 10060 – 9050 – 80500 – 800
Medium
100 – 140*100 – 140*60 – 9050 – 80> 800
High
Class DClass CClass BClass A
General Fill MaterialPercentage of optimum moisture content (standard
compaction)Median Annual
Rainfall (mm)
Rainfall Zone
Moisture Content Range forEmbankment Fill Materials
FromMRTS 04
Compaction Requirements(MRTS 04)
95% minimumClass C or D
(Low and medium rainfall zones)
90% minimum96% maximum
Class C or D(High rainfall zone)
95% minimumClass A or B
Road embankment
Characteristic Value of Relative
CompactionMaterialLocation
Stabilisation
Alternative to “Zoned Embankment”, stabilisation of the problematic soils can be considered. For example:• Expansive soil – Lime / cement / fly ash
• Dispersive soil – Gypsum / Lime
However it may not be cost-effective.
• Regional soil behaviour should be taken onto account
• Investigation to be carried out to identify problematic soils
• Problematic soils such as– Expansive soils– Dispersive soils– Erodible soils
can be encapsulated by better quality fill materials as per MRTS04 (MRS 11.04) for road embankment.
• Embankment Height >10m should be geotechnicallydesigned.
Summary
THANK YOU
AcknowledgmentAll staff within Geotechnical Branch