soil nail thesis presentation

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University of Technology, Sydney Faculty of Engineering & Information Technology School of Civil & Environmental Engineering Student : Victor Yeung Project No : S08 – 097 Student No: 10240810 Bachelor of Engineering ( Civil ) Supervisor: Dr. Behzad Fatahi

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Page 1: Soil Nail Thesis Presentation

University of Technology, Sydney

Faculty of Engineering & Information Technology

School of Civil & Environmental Engineering

Student : Victor Yeung

Project No : S08 – 097

Student No: 10240810

Bachelor of Engineering ( Civil )

Supervisor: Dr. Behzad Fatahi

Page 2: Soil Nail Thesis Presentation

Outline of Presentation

- What is slope failure ?- Type of landslide

- Factors causing landslide

- Slope stabilisation methods

- What is Soil Nail ?

- Construction procedure

- Quality control of Soil nailing

- SLOPE/W slope analysis software

- Case Study ( Hong Kong )

- Conclusion

Hong Kong , 1995

Page 3: Soil Nail Thesis Presentation

What is slope failure ?- The slope can not support itself

- Gravitational and seepage forces cause disturbing force

- Soil friction provide resisting force

- If disturbing moment > resisting moment

Slope will failure ( Landslide )

China

Page 4: Soil Nail Thesis Presentation

Type of landslide Fall type landslide Usually occurring in rock slopes, rock displacement and rock

fall with a very fast movement.

Newcastle , Australia

Page 5: Soil Nail Thesis Presentation

Type of landslideSlide type landslideSlides are usually caused by mass movements that present a well-

defined failure wedge and surface

Hong Kong , 1995

Page 6: Soil Nail Thesis Presentation

Type of landslideFlow type landslideFlow landslide is a continuous viscous slide involving soil or

rock. If material is clay or fine soil material, this flow is called mud flow

Hong Kong , 1990

Hong Kong , 2008

Page 7: Soil Nail Thesis Presentation

Major landslide in past history (Hong Kong & Australia)

Hong Kong

18 June 1972

Mid-level Kotewall Road. Two high-rise residential buildings collapsed due to large landslide and killed 67 people

Hong Kong , 1972

Page 8: Soil Nail Thesis Presentation

Major landslide in past history (Hong Kong & Australia)Australia

30 July 1997

A large section of steep mountainside below the Alpine Way road collapsed in Thredbo , NSW. 18 people died in this disaster. Australia , 1997

Page 9: Soil Nail Thesis Presentation

Factors causing landslide- Geometrical changes

- Surcharge

- Shocks and vibrations ( Earth quake, blasting)

- Change in water regime (Rainfall ,pipe leakage )

- Removal of vegetation ( Reduce tree root suction)

- Weathering ( Reduction of cohesion, desiccation )

Page 10: Soil Nail Thesis Presentation

Slope stabilisation methodsSurface protection

Shotcrete - Concrete sprayed on the slope surface

Masonry - Use stone pitching as a rigid surface cover

to prevent erosion and surface runoff.

Chunam - Cement sand mix material for surface

protection

Page 11: Soil Nail Thesis Presentation

Slope stabilisation methodsLandslide prevention

Soil nail Slope reinforced by the inserting steel reinforcing bars

Soil re-compactionExcavate loose soil and backfill re-compaction

Soil replacementUse other material replacing loose soil (No-fine concrete replacement)

Hong Kong

Hong Kong

Page 12: Soil Nail Thesis Presentation

Slope stabilisation methodsLandslide prevention

Bio- EngineeringUse tree root or plant root to prevent shallow slope failure

Sub-surface DrainageReduction of pore water pressure of slope

Stone ColumnsIncrease average shear resistance of soil along potential slip surface by using compacted stone

Hong Kong

Page 13: Soil Nail Thesis Presentation

Soil NailWhat is SOIL NAIL ?

Steel bar

Centraliser

Grout columnSoil nail head

Page 14: Soil Nail Thesis Presentation

Function of Soil Nail

Provide a resisting force against slope failure

Page 15: Soil Nail Thesis Presentation

Differences of Soil nail & Soil Anchor

Soil nail

- Non-prestressed

- Faster construction time

- Maintenance on soil nail is not necessary

Soil Anchor

- Prestressed tendon

- Longer construction time

-Maintenance is necessary

(Avoid loss of prestress in tendons)

Page 16: Soil Nail Thesis Presentation

Advantages of Soil nail

- Economy

- Fast construction

- Light construction equipment

- Adaptability to different soil types

- Flexibility

- Reinforcement Redundancy

Hong Kong

Hong Kong

Page 17: Soil Nail Thesis Presentation

Construction procedure of Soil nail

1. Drilling

2. Steel bar installation

3. Grouting

4. Soil nail head construction

Page 18: Soil Nail Thesis Presentation

Quality control of Soil nail

1. Soil nail Steel bar testing

2. Bleeding test & Flow Cone test (for Liquid grout )

3. Compressive strength test(for harden grout)

4. Pull out & proofing Tests

Bleeding Test

Flow cone test

Page 19: Soil Nail Thesis Presentation

Soil nail Design

Slope Failure analysis

- Limit equilibrium design approach

- Factor of Safety ( FOS ) calculation

Method of analysis- Ordinary / Swedish Method

- Bishop Method

- Janbu’s Method

-

- Other methods

Morgenstern-price’s Method

Page 20: Soil Nail Thesis Presentation

SLOPE/W slope analysis software

- Developed by GEO-SLOPE International Ltd. - Assessing the realistic FOS

Page 21: Soil Nail Thesis Presentation

Soil nail design procedure

1. Use SLOPE/W to analysis slope stability

2. Insert soil nails in the SLOPE/W model

3. Use trial and error method to determine the potential failure resisting force of soil nails

4. Use soil nail capacity calculation to determine bond length , bar size, spacing and inclination angle

5. Re- analysis the slope model use final design parameter

Page 22: Soil Nail Thesis Presentation

Design Criteria

1. Slope critical section FOS > Design requirement

2. Soil nail capacity checking must be satisfy the design requirement

Page 23: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

Background

1. Next to the sport centre , high risk (Consequence-to-life)

2. According to bore hole log record, cohesion=5kPa , Friction angle = 38o

3. Critical section – Height =12m , slope angle approximate= 60o

Location: Hong Kong ( Shek Kip Mei Sport Centre )

Page 24: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

Use bore hole log records to estimate the soil layering

Silty SandSilty Sand

Bedrock

Page 25: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

Use Morgenstern-Price’s Method Minimum FOS = 0.986

FOS (0.986) < 1.4 (HK requirement)

Page 26: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

Slip No FOS

1 1.112

20.986

(minimum)

3 1.157

4 1.367

5 1.572

Estimate potential slip surface

Page 27: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

After soil nail installed

minimum FOS = 1.52

FOS (1.52) >1.4 (require)

Page 28: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

Page 29: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

Row Nail Length (m)

Bond Length (m)

Inclination Angle

(degree)Nail

Spacing (m)Design

resisting force KN

A 12 3.3 15 2 55

B 12 3.8 15 2 50

C 8 4.3 15 2 20

D 8 4.2 15 2 15

E 8 5.7 15 2 8

Use Trial and error method to determine the preliminary soil nail parameter

Page 30: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

Row No.Level

(mPD)

Bar Length

(m)L

Bar Size (d)

(mm)D

Horizontal

Spacing (m)

S

Force per m

Width F (kN)

F

Force Required=F x S

Max. Allowable Tensile

Force

Ta > Tr

Tr (kN) Ta (kN) Check

Row E 58.80 8.0 25 2.0 8.00 16.00 79.66 O.K.Row D 56.80 8.0 25 2.0 15.00 30.00 79.66 O.K.Row C 54.80 8.0 25 2.0 20.00 40.00 79.66 O.K.Row B 52.80 12.0 32 2.0 50.00 100.00 141.62 O.K.Row A 50.80 12.0 32 2.0 55.00 110.00 141.62 O.K.

Maximum allowable tensile force of steel bar ( Final Checking )

Page 31: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

Maximum allowable force between steel & grout ( Final Checking )

Row No.

Level (mPD)

Bar Length

(m)

Bar Size (d)

(mm)

Horizontal

Spacing (m)

Free length

La (m)

Bond length Le

(m)

Force per m Width

F (kN)

Force Require

d

Max. Allowable

ForceTmax > Tr

Tr (kN) Tmax (kN)

Row E 58.8 8.0 25 2.0 4.70 3.30 8.00 16.00 205.26 O.K.

Row D 56.8 8.0 25 2.0 4.20 3.80 15.00 30.00 236.36 O.K.

Row C 54.8 8.0 25 2.0 3.70 4.30 20.00 40.00 267.46 O.K.

Row B 52.8 12.0 32 2.0 3.80 8.20 50.00 100.00 680.06 O.K.

Row A 50.8 12.0 32 2.0 2.30 9.70 55.00 110.00 804.46 O.K.

Page 32: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

Maximum allowable force between soil & grout ( Final Checking )

Row No.

Effective Vertical Stress

Force Mobilised

Total Force Mobilised

Force Require

dF.O.S.

F.O.S. > 2

sv (kPa)

Tf (kN)= ( 1.571 +

0.140 s’v ) x Le

CDG CDG Tf (kN) Tr (kN) Tf / Tr

Row E 68.00 36.65 36.65 16.00 2.29 O.K.

Row D 106.00 62.45 62.45 30.00 2.08 O.K.

Row C 144.00 93.58 93.58 40.00 2.34 O.K.

Row B 180.27 220.16 220.16 100.00 2.20 O.K.

Row A 158.57 230.92 230.92 110.00 2.10 O.K.

Page 33: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

Final Soil nail design summary

Row No.Level

(mPD)

Bar Length

(m)

Bar Size (d)

(mm)

Horizontal

Spacing (m)

Free length

La (m)

Bond length Le

(m)

Force per m

Width F (kN)

Force Require

d

Tr (kN)

Row E 58.80 8.0 25 2 4.70 3.30 8.00 16.00Row D 56.80 8.0 25 2 4.20 3.80 15.00 30.00Row C 54.80 8.0 25 2 3.70 4.30 20.00 40.00Row B 52.80 12.0 32 2 3.80 8.20 50.00 100.00Row A 50.80 12.0 32 2 2.30 9.70 55.00 110.00

Page 34: Soil Nail Thesis Presentation

Case Study ( Hong Kong )

After soil nail installed , the slope stability FOS value has been increased

Slip No FOS

1 -

2 1.534

31.529

(Minimum)

4 1.671

5 1.835

Page 35: Soil Nail Thesis Presentation

Conclusion- From the Case Study , the slope stability has been

significantly improved by Soil nailing

- Limit equilibrium method using Slope/W is an accurate approach to design soil nail walls in practice

- Soil nailing method has a simple design method and easy construction method

- Soil nail is the most cost-efficient solution for slope stabilisation

Page 36: Soil Nail Thesis Presentation

Thank youThank you

Any Questions ?Any Questions ?