1D Consolidation Analysis & Design

Transcription

1 SoilWorks 1D Consolidation Analysis & Design MIDAS Geotechnical Engineering Seminar NEW POSSIBILITY, DESIGN YOUR FUTURE Seongwan Bae MidasIT

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4 1D Consolidation Analysis & Design Part 1. Definitions Part 2. Analytical Overview Part 3. Process of Softground Design Part 5. Conclusions

5 Part 1. Definitions Soft Ground Compressible deposits such as Clay, silty Clay,clayey Silt. Very low permeability Initial and long term settlement 5

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) < >30 qc(tf/m 2 ) < >60 [Classification of Clay by Terzaghi & Peck] 6

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 7

8 Part 1. Definitions Softground Improvement Methods 8

9 1D Consolidation Analysis & Design Part 1. Definitions Part 2. Analytical Overview Part 3. Process of Softground Design Part 5. Conclusions

10 Part 2. Analytical Overview Overview [ 1D Consolidation] [ FEM Consolidation] 10

11 Part 2. Analytical Overview Settlement Calculation (Initial Settlement) Sand [ De Beer Method) ] [ B.K. Houng Graph Method ] 11

12 Part 2. Analytical Overview Settlement Calculation (Primary Consolidation) [ Notation and Terminology used foroedometer Compression Curves (frombalasubramaniam & Brenner, 1981) ] 12

13 Part 2. Analytical Overview Settlement Calculation (Primary Consolidation) Type Compression Index (C c ) method Volumetric Compression Index (m v ) method Initial Pore Ratio (e o ) 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 m v 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. 13

14 Part 2. Analytical Overview Settlement Calculation (Rebound of Cohesive Soil) Type Compression Index (C c ) method Volumetric Compression Index (m v ) method Initial Pore Ratio (e o ) 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. 14

15 Part 2. Analytical Overview Settlement Calculation (Secondary Consolidation) [Relation between Secondary Compression Ration and Water Content (frommesri, 1973) ] 15

16 Part 2. Analytical Overview Rate of Settlement (Degree of Consolidation) [ Example of Degree of Consolidation Curve for Construction Stage Analysis ] [ Rate of Settlement] [ Degree of Consolidation] 16

17 Part 2. Analytical Overview 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 ~

18 Part 2. Analytical Overview Calculation of Strength Increase Stability Analysis Analysis Method Simplified Bishop Simplified Janbu Vertical F Equilibrium Horizontal F Equilibrium Moment Equilibrium X X Spencer Morgenstern - Price Sarma (Vertical) Advantages Reduction in computing time Appliable for circular and non-circular failure surface Reduction in computin time Optimized for shallow failure surface Appliable for circular and non-circular failure surface Consider more accurate than simplified method Possible to estimate the internal vertical force Consider more accurate than Janbu Applicable for rock slope A modification of MP which reduces the iterations Disadvantages Inaccurate against horizontal force Conservative Results (F.S.) Need more iteration than simplified method Need more iteration than simplified method Need more iteration than simplified method 18

19 1D Consolidation Analysis & Design Part 1. Definitions Part 2. Analytical Overview Part 3. Process of Softground Design Part 5. Conclusions

20 Part 3. Process of Softground Design Process of Softground Design Check Design Criteria Total Construction Period Design level of embankment Design Criteria (Allowable Residual Settlement) Site Investigation Boring Test Lab Test -Consolidation Test -UU,CU Test Determine Material Properties C c, C v, C h E 0, P c, K v, K h S a Check Improvement Methods Stability Analysis Max.height of embankment Construction Stage Check Reinforcement 1D Consolidation Analysis Settlement and Duration Residual Settlement Drainage / Preloading Method Compare Reinforcement SCP / GCP Conterweight Fill Determine Improvement Method Determine Reinforcement Determine Drainage/Preloading Compare Drainage Plastic Board Drain Pack Drain Sand Drain Fiber Drain Check Points -Material properties -Stability -Waterlevel, site condition -Effect -Duration -Economy, Constructability Construction, Monitoring and Control 20

21 1D Consolidation Analysis & Design Part 1. Definitions Part 2. Analytical Overview Part 3. Process of Softground Design Part 5. Conclusions

22 Plan drawing of Soft Ground 6 1 st Zone

23 Preliminary Analysis Weak Layer Thickness Embankment Height Landfill Thickness N-value Embankment Landfill Soft Ground Waterlevel [ Model ] [ Input Data ] Total Settlement Consolidation Period Generated Settlement Residual Settlement Type Weak Layer Thickness (m) Embankment Height (m) Landfill Thickness (m) Softground Properties Top Bottom Number of Analysis Cases 5 X 5 X 2 = 50 case [ Output Data ] [ Preliminary Analysis Cases ] 23

24 Preliminary Analysis Weak Layer Thickness (D) Allowable Residual Settlement (cm) D 10m 10 10m D 30m m < D 30 [ Allowable Residual Settlement ]

25 Parametric Analysis Preloading Heights 6 1 st section Drainage Methods

26 Parametric Analysis <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 26

27 Parametric Analysis modeling process Copy & Paste Smart Surface(SS) Drag & Drop (Assign Material) Set Calculation Point Set Waterlevel Create Analysis Cases 27

28 Parametric Analysis modeling process Copy & Paste Smart Surface(SS) Drag & Drop (Assign Material) Set Calculation Point Set Waterlevel Create Analysis Cases 28

29 Parametric Analysis modeling process Copy & Paste Smart Surface(SS) Drag & Drop (Assign Material) Set Calculation Point Set Waterlevel Create Analysis Cases 29

30 Parametric Analysis modeling process Copy & Paste Smart Surface(SS) Drag & Drop (Assign Material) Set Calculation Point Set Waterlevel Create Analysis Cases 30

31 Parametric Analysis modeling process Copy & Paste Smart Surface(SS) Drag & Drop (Assign Material) Set Calculation Point Set Water level Create Analysis Cases 31

32 Parametric Analysis modeling process Copy & Paste Smart Surface(SS) Drag & Drop (Assign Material) Set Calculation Point Set Water level Create Analysis Cases 32

33 Parametric Analysis Result Analysis 33

34 Preloading Heights Preloading Heights 34

35 Preloading Heights 1 Preloading Heights Height Increase / Number of Increment 2 Analysis Cases for Each Increment 3 35

36 Preloading Heights Results Analysis 1 Analysis of Preloading Analysis Results

37 Preloading Heights Scheduled construction period(day) Degree of consolidation (%) Occurred settlement (m) Residual settlement (m) Allowable settlement(m) Remarks NG [ Settlement calculation results for scheduled construction period] Degree of consolidation (%) Duration (day) Occurred settlement (m) Residual settlement (m) [Degree of consolidation consolidation period settlement calculation results] 37

38 Residual settlement (m) Preloading Heights Section P/L height Duration (day) Degree of consolidation 90% Occurred settlement (m) Residual settlement (m) [Preloading Height Summary of review results of residual settlement] % 90% 95% P reloading height (m) [Preloading Height estimate for designated degree of consolidation] 38

39 Drain Spacing Drainage Methods, Reinforcement Methods, Drain Spacing Drainage Methods, Drain Spacing 39

40 Drain Spacing 1 Drain Spacing Construct PBD Analysis Cases for Each Spacing

41 Drain Spacing Results Analysis 1 Analysis of Drain Spacing Analysis Results

42 Drain Spacing - PBD Scheduled construction period(day) Degree of consolidation (%) Occurred settlement (m) Residual settlement (m) Allowable settlement(m) Remarks NG [ Settlement calculation results for scheduled construction period] Spacing Degree of consolidation (%) Occurred settlement (m) Residual settlement (m) Allowable residual settlement (m) Remarks 0.90m x 0.90m OK 1.10m x 1.10m OK 1.30m x 1.30m NG 1.50m x 1.50m NG 1.70m x 1.70m NG [ Improvement period for check is based on 730 date] 42

43 Drain Spacing - SCP Scheduled construction period(day) Degree of consolidation (%) Occurred settlement (m) Residual settlement (m) Allowable settlement(m) Remarks NG [ Settlement calculation results for scheduled construction period] Spacing Degree of consolidation (%) Occurred settlement (m) Residual settlement (m) Allowable residual settlement (m) Remarks 1.60m x 1.60m OK 1.80m x 1.80m OK 2.00m x 2.00m OK 2.20m x 2.20m NG 2.40m x 2.40m NG [ Improvement period for check is based on 730 date] 43

44 Softground-Slope Coupled Analysis Strength Increase, Slope Stability for each construction stage 44

45 Softground-Slope Coupled Analysis 1 45

46 Softground-Slope Coupled Analysis 1 Create Slope Models Guide Message 2 46

47 Softground-Slope Coupled Analysis Top Clay Surface Material Properties for each surface 1 Increase Parameters 2 47

48 Softground-Slope Coupled Analysis Slope Module 1 st stage stability 2 nd stage stability 3 rd stage stability 4 th stage stability 48

49 Softground-Slope Coupled Analysis Estimate the Max. heights of embankment during construction Softground Slope Softground Slope Module Module Module Module Single Stage Model Create Slope Model Max.Height of 1 st stage Multi Stage Model Create Slope Models Max.Height of 2 nd stage 49

50 Softground-Slope Coupled Analysis Max. heights of embankment for 1 st stage Softground Slope Softground Slope Module Module Module Module Single Stage Model Create Slope Model Max.Height of 1 st stage Multi Stage Model Create Slope Models Max.Height of 2 nd stage 50

51 Softground-Slope Coupled Analysis Estimate the Max. heights of embankment during construction Softground Slope Softground Slope Module Module Module Module Single Stage Model Create Slope Model Max.Height of 1 st stage Multi Stage Model Create Slope Models Max.Height of 2 nd stage 51

52 Softground-Slope Coupled Analysis Max. heights of embankment for 2 nd stage Softground Slope Softground Slope Module Module Module Module Single Stage Model Create Slope Model Max.Height of 1 st stage Multi Stage Model Create Slope Models Max.Height of 2 nd stage 52

53 Softground-Slope Coupled Analysis What if take the same time to model..?

54 1D Consolidation Analysis & Design Part 1. Definitions Part 2. Analytical Overview Part 3. Process of Softground Design Part 5. Conclusions

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 55

56 SoilWorks - Vision SoilWorks SoilWorks is Time is Money Time 56

57 SoilWorks - Vision International SoilWorks 57

58 SoilWorks - Vision International SoilWorks

59 SoilWorks Engineering Solution Partner 59