soilworks - midasen.midasuser.com/mail/20130417/session1.pdf · 2019-07-11 · soilworks 1d...

SoilWorks

1D Consolidation Analysis & Design

NEW POSSIBILITY,

DESIGN YOUR FUTURE

MidasIT Seongwan Bae

2013.04.04

MIDAS Geotechnical Engineering Seminar


Part 1. Definitions

Part 2. Analytical Overview

Part 3. Process of Softground Design

Part 4. Case Study

Part 5. Conclusions

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......... 08

......... 18

......... 20

......... 53

5

Geotechnical Solution for Practical Design

http://en.midasuser.com

Part 1. Definitions

Soft Ground

• Compressible deposits such as Clay, silty Clay,clayey Silt.

• Very low permeability

• Initial and long term settlement

6



Part 1. Definitions

Classification of Clay

Classification of Clay

Terzaghi & Peck (1967) Very Soft Soft Medium Stiff Very Stiff Hard

Szechy & Varga (1978) Very Soft Soft∼Medium Stiff Very Stiff Hard

SPT(N) ＜2 2∼4 4∼8 8∼15 15∼30 ＞30

qc(tf/m2) ＜5 5∼15 15∼30 30∼60 ＞60

[Classification of Clay by Terzaghi & Peck]

7



Part 1. Definitions

Problems in Soft Ground

• Initial and long term settlements

during and after construction

• Differential settlement on

adjacent structures, services(road)

• Heaving or Boiling

• Reduction of bearing capacity…

8



Part 1. Definitions

Softground Improvement Methods

http://www.penta-ocean.co.jp/english/business/civil/softground.html


Part 1. Definitions



Part 4. Case Study

Part 5. Conclusions

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10




Overview

[ 1D Consolidation]

[ FEM Consolidation]

11



Sand


Settlement Calculation (Initial Settlement)

[ De Beer Method) ]

[ B.K. Houng Graph Method ]

12




Settlement Calculation (Primary Consolidation)

[ Notation and Terminology used forOedometer Compression

Curves (fromBalasubramaniam & Brenner, 1981) ]

13




Settlement Calculation (Primary Consolidation)

Type Compression Index (Cc)

method

Volumetric Compression

Index (mv) method Initial Pore Ratio (eo) method

Schematic

Diagram

Settlement

Calculation

Remarks

Used when consolidation test

cases are few or none and

when an approximate

settlement calculation using

physical properties is

performed.

The level of variation of mv in

the overconsolidated domain

is high, which results in a

large margin of errors. But

the level is relatively good in

the normally consolidated

domain.

In case a large amount of test

data renders a big variation in

the e-logP curve, the

settlement calculation by this

theoretical method is rather

difficult. It is not commonly

used in practice.

14




Settlement Calculation (Rebound of Cohesive Soil)

Type Compression Index (Cc)

method

Volumetric Compression

Index (mv) method Initial Pore Ratio (eo) method

Schematic

Diagram

Rebound

Calculation

Remarks

In the method, the rebound

is calculated using the

removed stress and,

the slope of the e-logP curve

after the removal of the load.

In the method, the rebound

is calculated using the

removed stress and,

Mv after the removal of the

load.

In the method, the rebound is

calculated using the void ratios

before and after removal of the

load.

15




Settlement Calculation (Secondary Consolidation)

[Relation between Secondary Compression Ration and Water

Content (fromMesri, 1973) ]

16




Rate of Settlement (Degree of Consolidation)

[ Example of Degree of Consolidation Curve for Construction Stage Analysis ]

[ Rate of Settlement] [ Degree of Consolidation]

17




Calculation of Strength Increase

Type Skempton Hansbo Triaxial Compression Test

Empirical

Equations

IP = Plastic Index

WL = Liquid Limit

Φ = Friction angle from CU Test

Type Strength Increment Ratio (m)

Clay 0.25 ~ 0.30

Silt 0.30 ~ 0.45

silty Clay 0.25 ~ 0.40

Peat 0.35 ~ 0.50

18




Calculation of Strength Increase – Stability Analysis

Analysis

Method

Vertical F

Equilibrium

Horizontal F

Equilibrium

Moment

Equilibrium Advantages Disadvantages

Simplified

Bishop ○ X ○

• Reduction in computing

time

• Appliable for circular and

non-circular failure surface

• Inaccurate against

horizontal force

Simplified

Janbu ○ ○ X

• Reduction in computin time

• Optimized for shallow

failure surface

• Conservative Results

(F.S.)

Spencer ○ ○ ○

• Appliable for circular and

non-circular failure surface

• Consider more accurate

than simplified method

• Need more iteration


Morgenstern -

Price ○ ○ ○

• Possible to estimate the

internal vertical force

• Consider more accurate

than Janbu



Sarma

(Vertical) ○ ○ ○

• Applicable for rock slope

• A modification of MP which

reduces the iterations




Part 1. Definitions



Part 4. Case Study

Part 5. Conclusions

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20




Process of Softground Design

Check Design Criteria

Site Investigation

Determine Material Properties

Check Improvement Methods

Max.height of embankment

Construction Stage

Check Reinforcement

Stability Analysis

Settlement and Duration

Residual Settlement

Drainage / Preloading Method

1D Consolidation Analysis

SCP / GCP

Conterweight Fill

Compare Reinforcement

Determine Reinforcement

Determine Drainage/Preloading

Determine Improvement Method

Plastic Board Drain

Pack Drain

Sand Drain

Fiber Drain

Compare Drainage

Construction,

Monitoring and Control

Total Construction Period

Design level of embankment

Design Criteria

(Allowable Residual Settlement)

Boring Test

Lab Test

-Consolidation Test

-UU,CU Test

Cc , Cv , Ch

E0 , Pc , Kv , Kh

Sa

Check Points

-Material properties

-Stability

-Waterlevel, site condition

-Effect

-Duration

-Economy, Constructability


Part 1. Definitions



Part 4. Case Study

Part 5. Conclusions

......... 03

......... 08

......... 18

......... 20

......... 53

22



Part 4. Case Study

Plan drawing of Soft Ground

2

2

2

3

2

2

2

3

2 2

2

6 1st Zone

32

23



Part 4. Case Study

Preliminary Analysis

[ Model ]

Type 1 2 3 4 5 Number of

Analysis Cases

Weak Layer

Thickness (m) 2 4 6 8 10

5 X 5 X 2 = 50 case

Embankment

Height (m) 3 6 9 12 15

Landfill Thickness

(m) 2

Softground

Properties Top Bottom

Soft Ground

Embankment

Landfill

Weak Layer Thickness

Embankment Height

N-value

Waterlevel

Total Settlement

Consolidation Period

Generated Settlement

Residual Settlement

Landfill Thickness

[ Input Data ]

[ Output Data ] [ Preliminary Analysis Cases ]

24



Part 4. Case Study

Preliminary Analysis

1

2

3

4

Weak Layer Thickness (D) Allowable Residual Settlement (cm)

D ≤ 10m 10

10m ≤ D ≤ 30m 20

30m ＜ D 30

[ Allowable Residual Settlement ]

25



Part 4. Case Study

Parametric Analysis

2

2

2

3

2

2

2

3

2 2

2

6 1st section

32

Drainage Methods

Preloading Heights

26



<Model>

Modeling Process : CAD section import Smart Surface Drag &Drop (Assign Material Properties)

1D Consolidation Analysis

Multi Analysis

Parametric Analysis for Max. Drain Spacing

Parametric Analysis for Min. Preloading Height

Smart Result

Result Analysis -> Report Generation

Softground – Slope Coupled Analysis

Part 4. Case Study

Parametric Analysis

27



Copy & Paste

Smart Surface(SS) Drag & Drop

(Assign Material) Set Calculation Point

Set Waterlevel

Create Analysis Cases

Part 4. Case Study

Parametric Analysis – modeling process

28



Copy & Paste Smart Surface(SS) Drag & Drop


Set Waterlevel


Part 4. Case Study


29




(Assign Material)

Set Calculation Point Set

Waterlevel Create Analysis

Cases

Part 4. Case Study


30




(Assign Material) Set Calculation

Point Set

Waterlevel Create Analysis

Cases

Part 4. Case Study


31





Set Water

level


Part 4. Case Study


32



Part 4. Case Study




Set Water

level

Create Analysis

Cases

33



Part 4. Case Study

Parametric Analysis – Result Analysis

34



Part 4. Case Study

Preloading Heights

Preloading Heights

35



Part 4. Case Study

Preloading Heights

1

2

3

Preloading Heights

Height Increase / Number of Increment

Analysis Cases for Each Increment

36



Part 4. Case Study

Preloading Heights

1

2

3

Results Analysis

Analysis of Preloading Analysis Results

37



Part 4. Case Study

Preloading Heights

Degree of consolidation (%) 55 60 65 70 75 80 85 90 95 99

Duration (day) 371 445 530 627 741 882 1063 1318 1755 2769

Occurred settlement (m) 0.5884 0.6418 0.6953 0.7488 0.8023 0.8558 0.9093 0.9628 1.0162 1.0590

Residual settlement (m) 0.4814 0.4279 0.3744 0.3209 0.2674 0.2139 0.1605 0.1070 0.0535 0.0107

Scheduled construction

period(day)

Degree of

consolidation (%)

Occurred

settlement (m)

Residual

settlement (m)

Allowable

settlement(m) Remarks

730 74.54 0.7974 0.2723 0.1000 NG

[ Settlement calculation results for scheduled construction period]

[Degree of consolidation – consolidation period – settlement calculation results]

38



0 0.5 1 1.5 2 2.5

Preloading height (m)

-0.1

0

0.1

0.2

Resid

ual settle

ment (m

)

85%90%95%

Part 4. Case Study

Preloading Heights

Section P/L height

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00

Degree of

consolidation

90%

Duration (day) 1318 1318 1318 1318 1318 1318 1318 1318 1318 1318

Occurred

settlement (m) 0.9721 0.9812 0.9900 0.9987 1.0071 1.0153 1.0233 1.0312 1.0389 1.0464

Residual

settlement (m) 0.0976 0.0886 0.0797 0.0711 0.0626 0.0544 0.0464 0.0385 0.0309 0.0233

[Preloading Height – Summary of review results of residual settlement]

[Preloading Height estimate for designated degree of consolidation]

39



Part 4. Case Study

Drain Spacing

Drainage Methods, Reinforcement Methods,

Drain Spacing

Drainage Methods, Drain Spacing

40



Part 4. Case Study

Drain Spacing

1

2

3

Construct PBD

Drain Spacing

Analysis Cases for Each Spacing

41



1

2

3

Part 4. Case Study

Drain Spacing

Results Analysis

Analysis of Drain Spacing Analysis Results

42




period(day)

Degree of

consolidation (%)

Occurred

settlement (m)

Residual

settlement (m)

Allowable


730 74.54 0.7974 0.2723 0.1000 NG


Part 4. Case Study

Drain Spacing - PBD

Spacing Degree of

consolidation (%)

Occurred

settlement (m)

Residual

settlement (m)

Allowable

residual settlement

(m)

Remarks

0.90m x 0.90m 95.69 1.0236 0.0461 0.1000 OK

1.10m x 1.10m 91.63 0.9802 0.0895 0.1000 OK

1.30m x 1.30m 88.05 0.9419 0.1278 0.1000 NG

1.50m x 1.50m 85.24 0.9118 0.1579 0.1000 NG

1.70m x 1.70m 83.10 0.8889 0.1808 0.1000 NG

[ Improvement period for check is based on 730 date]

43



Part 4. Case Study

Drain Spacing - SCP


period(day)

Degree of

consolidation (%)

Occurred

settlement (m)

Residual

settlement (m)

Allowable


730 74.54 0.6598 0.2253 0.1000 NG


Spacing Degree of

consolidation (%)

Occurred

settlement (m)

Residual

settlement (m)

Allowable

residual settlement

(m)

Remarks

1.60m x 1.60m 94.40 0.7519 0.0446 0.1000 OK

1.80m x 1.80m 91.61 0.7448 0.0682 0.1000 OK

2.00m x 2.00m 89.03 0.7349 0.0906 0.1000 OK

2.20m x 2.20m 86.79 0.7247 0.1103 0.1000 NG

2.40m x 2.40m 84.92 0.7154 0.1271 0.1000 NG

[ Improvement period for check is based on 730 date]

44



Part 4. Case Study

Softground-Slope Coupled Analysis

Strength Increase, Slope Stability for each construction stage

45



Part 4. Case Study


1

46



Part 4. Case Study


1

2

Create Slope Models

Guide Message

47



Part 4. Case Study


1

2

Top Clay Surface

Increase Parameters

Material Properties for each surface

48



Part 4. Case Study


Slope Module 1st stage stability 2nd stage stability 3rd stage stability 4th stage stability

49



Softground

Module

•Single Stage Model

•Create Slope Model

Slope

Module

•Max.Height of 1st

stage

Softground

Module

•Multi Stage Model

•Create Slope Models

Slope

Module

•Max.Height of 2nd

stage

Part 4. Case Study


Estimate the Max. heights of embankment during construction

50



Part 4. Case Study


Max. heights of embankment for 1st stage

Softground

Module



Slope

Module


stage

Softground

Module



Slope

Module


stage

51



Part 4. Case Study


Estimate the Max. heights of embankment during construction

Softground

Module



Slope

Module


stage

Softground

Module



Slope

Module


stage

52



Part 4. Case Study


Max. heights of embankment for 2nd stage

Softground

Module



Slope

Module


stage

Softground

Module



Slope

Module


stage

53



1

2

Part 4. Case Study


What if… take the same time to model..?


Part 1. Definitions



Part 4. Case Study

Part 5. Conclusions

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......... 08

......... 18

......... 20

......... 53

55



Part 5. Conclusions

Conclusions

• Design Criteria

– In terms of both serviceability and costs

• Site Investigation

– Geological information and reliable parameters for analysis

• Design Process

– Ensure both stability of embankment and residual settlements

• Monitoring

– Performance of embankment during and after construction

56



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57



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soilworks - midasen.midasuser.com/mail/20130417/session1.pdf · 2019-07-11 · soilworks 1d...

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